,a ,century's ,progress                 
,,in                                    
,astronomy                              
,,by                          ,,hector  
,,macpherson1 ,jun4                     
,,member ,,of ,,the ,,soci,t            
,,astronomique ,,de ,,france2           
,,member ,,of ,,the ,,soci,t ,,belge    
,d',,astronomie2                        
,,author ,,of #8,,astronomers ,,of      
,,to-,,day'                             
,,william ,,blackwood ,,and ,,sons      
,,edinburgh ,,and ,,london              
,,mcmvi                           ,all  
,rights reserved                        
,,preface4      ,the present volume     
originated in a desire to present1 in   
small compass1  a record of the         
marvellous progress in astronomy during 
the past hundred  years4 ,indebtedness  
should be acknowledged to the valuable  
works of  ,professor ,newcomb1          
,professor ,schiaparelli1 ,professor    
,lowell1 ,professor  ,young1 ,sir       
,robert ,ball1 ,mr ,gore1 ,m4           

,flammarion1 and ,miss ,clerke1 who1 as 
the historian of modern astronomy1      
occupies a place at once  authoritative 
and unique4    ,portions of ,chapters   
,,ii4 and ,,xii4 have already appeared  
in the form of  an article on the       
,construction of the ,heavens1          
contributed by the writer  to the       
,american periodical1 #8,popular        
,astronomy4'      ,balerno1             
,mid-,lothian1        ,october #aijf4   
,,contents4                             
,,page    ,,chapter ,i4                 
#a                                      
,,herschel ,,the ,,pioneer4             
,influence of ,herschel's work--,his    
characteristics--,birth and             
early years--,emigration to             
,england--,caroline                     
,herschel--,discovery of                
,uranus--,king's ,astronomer--,latter   
years and death--,death of ,caroline    
,herschel    ,,chapter ,,ii4            
#ae                                     
,,herschel ,,the ,,discoverer4          

,solar researches--,study of ,venus--,of
 ,mars--,the                            
,asteroids--,jupiter--,saturn--,discover
y of satellites--,uranian               
satellites--,cometary                   
researches--,motion of the ,solar       
,system--,discovery of binary           
stars--,clusters and                    
nebul--,nebulous stars--,the ,nebular   
,hypothesis--,star-gauging--,the        
disc-theory--,subordinate               
clusters--,abandonment of the           
disc-theory--,second method of          
star-gauging--,estimate of ,herschel's  
work    ,,chapter ,,iii4                
#dc                                     
,,the ,,sun4        ,schwabe and the    
sun-spot period--,researches of ,wolf1  
,lamont1            ,sabine1            
,gautier--,observations of ,carrington  
and            ,sprer--,career and work 
of ,fraunhofer--,spectrum               
analysis--,work of ,kirchhoff--,solar   
eclipse work--,the ,solar               
prominences--,janssen and               

,lockyer--,huggins and ,zllner--,work   
of ,young--,the ,italian                
spectroscopists1 ,secchi1 ,respighi1    
,tacchini--,career of ,tacchini--,the   
reversing layer--,the                   
,corona--,doppler's principle--,rotation
 of the ,sun--,work of                  
,dunr--,janssen's solar atlas--,maunder 
and magnetism--,solar                   
theories--,distance of the              
,sun--,summary    ,,chapter ,,iv4       
#fe                                     
,,the ,,moon4        ,life and work of  
,schrter--,of ,mdler--,of               
,schmidt--,changes on the               
,moon--,selenography in ,england--,lunar
 atmosphere--,lunar                     
photography--,work of ,w4 ,h4           
,pickering--,the new                    
,selenography--,the ,moon's             
heat--,motion of the                    
,moon--,acceleration of the ,moon's mean
 motion--,work of            ,laplace1  
,adams1 ,delaunay    ,,chapter ,v4      
#hj                               ,,the 

,,inner ,,planets4        ,the problem  
of ,vulcan--,mercury--,work of          
,schrter--,schiaparelli1            his 
life and work--,work of                 
,lowell--,spectrum of                   
,mercury--,venus--,rotation period3 work
 of ,schrter1 ,di ,vico1                
,schiaparelli1 ,tacchini1               
,lowell--,atmosphere and surface of     
,venus--,the ,earth3 variation of       
latitude--,mars--,rotation of           
,mars--,surface--,discovery of          
canals--,work of ,schiaparelli and      
,lowell--,interpretation of the         
canals--,the theory of                  
intelligent life--,spectrum of          
,mars--,satellites--,the                
,asteroids--,bode's law--,work of       
,piazzi and ,olbers--,application       
of photography by ,wolf--,discovery of  
,eros    ,,chapter ,,vi4                
#ajc                               ,,the
 ,,outer ,,planets4        ,physical    
condition of ,jupiter--,work of ,zllner 
and ,proctor--,the            red       

spot--,satellites--,discovery of fifth  
satellite--,sixth and            seventh
 satellites--,rings of ,saturn3 ,bond1  
,maxwell1            ,keeler--,struve's 
theory--,globe of ,saturn--,new         
satellites--,uranus and its             
satellites--,discovery of               
,neptune--,adams and ,le                
,verrier--,satellite--,trans-,neptunian 
planets    ,,chapter ,,vii4             
#abc                                    
,,comets4        ,life and work of      
,olbers--,his repulsion theory--,life   
and work of            ,encke--,his     
comet--,biela's comet--,faye's          
comet--,return of            ,halley's  
comet--,donati's comet--,comet of       
#ahfa--,spectroscopic            study  
of comets--,theory of                   
,brdikhine--,spectra of                 
comets--,comets of #ahhj and #ahhb--,the
 capture theory--,cometary              
photography    ,,chapter ,,viii4        
#ach                                    
,,meteors4        ,meteoric shower of   

#ahcc--,work of ,olmsted--,work of      
,erman and            ,kirkwood--,of ,h4
 ,a4 ,newton--,adams and the meteoric   
orbit--,shower of #ahff--;,connection of
 comets and meteors--,work            of
 ,schiaparelli--,shower of meteors in   
#ahgb--#8,le ,stelle                    
,cadenti'--,meteoric observation--,a4   
,s4 ,herschel--,work of                 
,denning--,stationary radiants--,bolides
 and aerolites--,origin            of   
aerolites    ,,chapter ,,ix4            
#aej                                    
,,the ,,stars4        ,distance of the  
stars--,life and work of                
,bessel--,studies of                    
,struve--,life and work of              
,henderson--,work of ,peters1 ,otto     
,struve1 ,brnnow1 and ,ball--,measures  
of ,gill--,parallax of                  
first-magnitude stars--,relative and    
absolute parallax--,work            of  
,kapteyn--,application of               
photography--,star-catalogues--,argeland
er's                                    

#8,durchmusterung'--,work of            
,schnfeld--,work of ,gould--,the #8,cape
            ,photographic               
,durchmusterung'--,work of ,gill and    
,kapteyn--,international chart of the   
heavens--,work of                       
,peck--,proper motions of the           
stars--,star-drift--,discoveries of     
,proctor and ,flammarion--,radial       
motion--,work of ,huggins1              
,vogel1 and ,campbell--,solar motion    
,,chapter ,x4                           
#afi                            ,,the   
,,light ,,of ,,the ,,stars4        ,work
 of ,fraunhofer and ,donati--,life and  
work of ,secchi--,his            types  
of spectra--,life and work of           
,huggins--,photography of               
spectra--,life and work of ,vogel--,his 
classification of                       
spectra--,work of ,dunr--,of            
,pickering--,spectroscopic              
catalogues--,analysis of                
spectra--,stellar photometry--,life and 
work of ,e4 ,c4 ,pickering--,variable   

stars--,work of                         
,goodricke--,of ,argelander1 ,schmidt1  
,heis1 ,schnfeld--,studies            of
 ,dunr--,of ,gore--,photographic        
discoveries--,classification--,algol    
variables3 their                        
explanation--,explanation of other      
variables--                             
,argus--,temporary stars--,of #ahdh--,of
 #ahff--,of #ahgf--,of #ahhe--,of       
#ahib--,photographic discoveries--,nova 
,persei1 #aija--,new star            of 
#aijc--,theories of temporary stars     
,,chapter ,,xi4                         
#aig                          ,,stellar 
,,systems ,,and ,,nebul4        ,life   
and work of ,john ,herschel--,binary    
stars--,computation of                  
orbits--,work of ,wilhelm ,struve--,of  
,otto ,struve--,of                      
,burnham--,satellites of ,sirius and    
,procyon--,astronomy of the             
invisible--,work of ,pickering and      
,vogel--,spectroscopic                  
binaries--,work of ,blopolsky and       

,campbell--,star-clusters--,nature of   
nebul--,spectroscopic work            of
 ,huggins--,of ,copeland--,nebular      
photography--,work of                   
,roberts1 ,barnard1 ,wolf--,of ,keeler  
,,chapter ,,xii4                        
#bad            ,,stellar ,,distribution
 ,,and ,,the ,,structure ,,of ,,the     
,,universe4        ,work of ,john       
,herschel--,researches of ,wilhelm      
,struve--,extinction            of      
light--,mdler's 8central                
sun0--,distribution of                  
nebul--,work of ,proctor--,aggregation  
of stars on the                         
,galaxy--,work of ,gore and             
,schiaparelli--,studies of              
,gould--,researches of ,kapteyn--,of    
,newcomb--,is the ,universe             
limited8 ,newcomb's                     
argument--,observations of              
,celoria--,researches of                
,seeliger--,external ,universes--,gore's
            speculations    ,,chapter   
,,xiii4                                 

#bbg                                    
,,celestial ,,evolution4                
,laplace's nebular                      
hypothesis--,helmholtz and solar        
contraction--,theories of solar         
heat--,objections to ,laplace's         
theory--,faye's hypothesis--,ball's     
exposition--,the meteoritic             
theory of ,proctor--,its extension by   
,lockyer--,evolution of            the  
stars--,vogel's order of                
evolution--,tidal friction3 work        
of ,darwin--,see's explanation of double
 stars--,future of the                  
,universe                             ,a
 ,,century',s ,,progress ,,in           
,,astronomy4                            
,,chapter ,i4                           
,,herschel ,,the ,,pioneer4      ,in    
astronomy1 as in other sciences1 the    
past hundred years has been a  period of
 unparalleled progress4 ,new methods    
have been devised1 fresh  discoveries   
have been made1 new theories have been  
propounded2 the field  of work has      

widened enormously4 ,in fact1 the       
science of the heavens has  become not  
only boundless in its possibilities1 but
 more awe-inspiring  and marvellous4    
,to whom in the main is this great      
advance due8 ,to the great pioneer of   
what may be called modern               
astronomy--,william ,herschel4 ,not only
 did  ,herschel reconstruct the science 
and widen its bounds1 but his powerful  
genius directed the course of nineteenth
 century research4 ,as an  astronomical 
observer he has never been surpassed4   
,in the breadth of his  views he was    
equalled only by ,newton2 and indeed he 
excelled ,newton in  his unwearied      
observations and his sweeping           
conceptions of the ,universe4  ,to quote
 his own remark to the poet ,campbell1  
he 8looked farther into  space than ever
 human being did before him40           
,herschel studied astronomy in all its  
aspects4 ,in all the branches of  modern
 astronomy he was a pioneer4 ,he        
observed the ,sun1 ,moon1 and  planets1 

devoting special attention to ,mars and 
,saturn4 ,he doubled the  diameter of   
the ,solar ,system by the discovery of  
,uranus4 ,he discovered  several        
satellites and studied comets4 ,he was  
pre-eminently the founder  of sidereal  
astronomy4 ,he discovered binary stars1 
thus tracing the law  of gravitation in 
the distant star-depths2 while to him is
 due the  credit of the discovery of the
 motion of the ,solar ,system4 ,he      
founded  the study of star-clusters and 
nebul1 propounded the nebular           
hypothesis1 and devised two methods of  
star-gauging4 ,above all1 he was  the   
first to attempt the solution of one of 
the noblest problems ever  attacked by  
man--the structure of the ,universe4 ,in
 fact1 the latter  problem was the end  
and aim of his observations4 ,as ,miss  
,clerke remarks1  8,the magnificence of 
the idea1 which was rooted in his mind  
from the  start1 places him apart from  
and above all preceding observers40     
,most of  the departments of modern     

astronomy find a meeting-place in       
,herschel1 as  the branches run to the  
root of the tree4 ,he discussed         
astronomy from  every point of view4    
,before1 however1 proceeding to examine 
the work of  this great man1 it is well 
to note a few of his characteristics4   
,these  characteristics1 once           
understood1 give us the key to his      
researches4  ,before we can master      
,herschel the astronomer we must        
understand ,herschel  the man4          
,notwithstanding the fact that ,herschel
 spent most of his life in  ,england1   
and that he is included in the          
#8,dictionary of ,national  ,biography1'
 he was pre-eminently a ,german4 ,like  
most ,germans his style  of writing was 
somewhat obscure1 and this was          
emphasised when he wrote  in ,english1  
owing to his imperfect command of the   
language4 ,had he  written in ,german as
 well as in ,english1 he would probably 
have been  better understood in his     
native country1 where erroneous views of

 his  theories were long entertained4   
,even so distinguished an astronomer as 
,wilhelm ,struve1 when translating      
,herschel's papers into ,german1 made a 
mistake when translating a certain      
passage1 which leaves the erroneous     
impression that ,herschel believed the  
,universe to be infinite--a mistake     
which would not have arisen had he      
written in ,german4    ,the student of  
,herschel should also be careful in     
quoting the views of  the great         
astronomer4 ,had ,herschel at the close 
of his life written a  volume containing
 his final views on the construction of 
the heavens1  this would not have been  
necessary2 but ,herschel did not write  
such a  volume4 ,his researches were    
embodied in a series of papers          
communicated  to the ,royal ,society    
from #aghj to #ahah4 ,as he observed the
 heavens his  opinions progressed1 so   
that a statement of his views at any    
given time  was by no means a statement 
of his final opinions4 ,the late ,r4 ,a4

  ,proctor1 who was the first great     
exponent of ,herschel in ,england1 has  
well said3 8,it seems to have been      
supposed that his papers could be       
treated as we might treat such a work as
 ,sir ,j4 ,herschel's #8,outlines of    
,astronomy'2 that extracts might be made
 from any part of any paper  without    
reference to the position which the     
paper chanced to occupy in  the entire  
series40    ,herschel1 like the true    
student of nature1 held theories very   
lightly4  ,they were to him but roads to
 the truth4 ,unlike many scientists1 he 
did  not interpret observations by      
hypothesis3 he framed his theories to   
fit  his observations4 ,if he found that
 a certain theory did not agree with    
what he actually saw in the heavens1 he 
abandoned it3 he did not  hesitate to   
change his views as his investigations  
proceeded4 8,no fear  of #8committing   
himself1'0 says ,miss ,clerke in her    
admirable work on #8,the  ,herschels1'  
8deterred him from imparting the        

thoughts that accompanied  his          
multitudinous observations4 ,he felt    
committed to nothing but truth40    ,in 
the mind of ,herschel imagination and   
observation were marvellously  blended4 
,he was a philosophical astronomer4     
,although his imagination was  a very   
vivid one he did not allow his fancies  
to run away with him1 as  ,kepler       
sometimes did3 on the other hand1 he did
 not1 like ,flamsteed1  refrain from    
speculating altogether4 8,we ought10 he 
wrote in #aghe1 8to  avoid two opposite 
extremes4 ,if we indulge a fanciful     
imagination1 and  build worlds of our   
own1 we must not wonder at our going    
wide from the  path of truth and nature4
 ,on the other hand1 if we add          
observation to  observation1 without    
attempting to draw not only certain     
conclusions but  also conjectural views 
from them1 we offend against the very   
end for  which only observations ought  
to be made40    ,these                  
characteristics--the lightness with     

which he held his theories1 his  vivid  
imagination1 and his philosophical      
reasoning--are the secrets of           
,herschel's success as an astronomer4   
,nearly all his ideas and  speculations 
have been confirmed4 ,as ,arago has     
said1 8,we cannot but feel  a deep      
reverence for that powerful genius that 
has scarcely ever erred40  ,herschel1   
like all other great students of        
,nature1 was deeply religious4  ,he     
could not observe the heavens without   
feeling awed at the marvels  which his  
telescopes revealed4 ,in his own words1 
8,it is surely a very  laudable thing to
 receive instruction from the ,great    
,workmaster of  ,nature40    ,friedrich 
,wilhelm ,herschel1 born in ,hanover on 
,november #ae1 #agch1 was  the fourth   
child of ,isaac ,herschel1 an oboist in 
the band of the  ,hanoverian ,guard4    
,isaac ,herschel1 a native of ,dresden1 
was an  accomplished musician1 and all  
his children1 ten in number1 inherited  
his talent4 ,of these ten1 six survived1

 and only two became famous4  ,these    
were ,william1 the great astronomer1 and
 his sister ,caroline 7born  on ,march  
#af1 #agej71 who became a student of the
 heavens only second to  her brother4   
,at the garrison school in ,hanover1    
where the ,herschels were educated1     
,william ,herschel showed intense love  
and aptitude for learning1 and was  more
 diligent and persevering than his      
brother ,jacob1 his senior by four      
years4 ,in #agec he became oboist in the
 band of the ,hanoverian ,guard in      
which his father was now bandmaster4 ,in
 her valuable memoirs1 his sister       
relates that her father was very        
interested in astronomy1 and that he    
taught his children the names of the    
constellations4 ,william became  devoted
 to the science1 and constructed a small
 celestial globe on which  equator and  
ecliptic were engraved4 ,but his studies
 were much hampered4  ,his mother had a 
great dislike to learning3 she had no   
sympathy with  aspirations1 and tried to

 prevent her children becoming well     
educated4  ,above all1 the ,hanoverian  
,guard was ordered to ,england in #agee1
 when a  ,french invasion was feared1   
and to that country ,herschel proceeded1
  along with his father and brother4    
,returning to ,germany in #agef1 the    
,hanoverian ,guard was employed the     
following year in the ,seven ,years'    
,war4 ,hanover was invaded by the       
,french1 and1 conscription being the    
rule1 the musicians were not  exempted  
from service4 ,under the command of the 
,duke of ,cumberland the  ,guard        
suffered a terrible defeat at           
,hastenbeck4 ,william ,herschel spent   
the night after the battle in a ditch1  
and decided that soldiering would  not  
be his profession4 ,he deserted1 and1   
with the consent of his  parents1 he    
sailed for ,england4 ,after his arrival 
at ,dover1 he wandered  through the     
country in search of musical employment4
 ,at length1 in #agfj1  he was appointed
 to train the band of the ,durham       

,militia1 and four years  later paid a  
secret visit to ,hanover1 where he was  
welcomed by his  father1 whose health   
was now failing1 and by his sister      
,caroline4 ,in the  following year he   
was promoted to the post of organist at 
,halifax1 and  in #agff he removed to   
,bath as oboist in ,linley's ,orchestra4
 ,finally1 in  #agfg1 he became organist
 in the new ,octagon ,chapel at ,bath4  
,herschel was  now twenty-nine years    
old1 and known as a famous musician4 ,as
 ,miss  ,clerke remarks3 8,the ,octagon 
,chapel soon became a centre of         
fashionable  attraction1 and he soon    
found himself lifted on the wave of     
public  favour4 ,pupils of high rank    
thronged to him1 and his lessons often  
mounted to thirty-five a-week40    ,in  
the year of his appointment his father  
died1 aged sixty1 after a life  of      
trouble and hardship4 ,his death was a  
great blow to his daughter  ,caroline1  
whom he had educated when her mother was
 from home4 ,caroline  ,herschel was    

naturally possessed of musical ability1 
but her mother and  elder brother had   
determined that she should be a         
housemaid1--a  determination which      
,william1 who was devotedly attached to 
his sister1  opposed4 ,finally1 in      
#aggb1 he visited ,hanover1 and took his
 sister to  ,england with him to act as 
his housekeeper4 ,but for her unwearied 
devotion it is doubtful whether ,william
 ,herschel would have become the  great 
astronomer4    ,about the time of his   
appointment in ,bath ,herschel commenced
 the study  of languages and            
mathematics1 reading ,maclaurin's       
#8,fluxions' and  ,ferguson's           
#8,astronomy4' ,the perusal of the      
latter volume revived his  love for     
astronomy4 ,after fourteen or sixteen   
hours' teaching he would  retire to his 
bedroom and read of the wonders of the  
heavens4 ,his  interest increased as he 
proceeded1 until1 in his own words1 8,i 
resolved  to take nothing upon trust1   
but to see with my own eyes all that    

other  men had seen before me40         
,accordingly he hired a small reflector4
  ,inquiring the price of a larger      
instrument1 he found it to be quite     
beyond his means4 ,then in #aggb1 when  
his sister came to keep his house  for  
him1 he resolved to make his own        
telescope4 ,first he tried the  fitting 
of lenses into pasteboard tubes1 but    
this being a total failure1  he bought  
the apparatus of a ,quaker optician who 
had constructed1 or  attempted to       
construct1 reflecting telescopes4 ,in   
,june #aggc1 assisted by  his sister and
 by his brother ,alexander1 then in     
,bath1 he commenced  work4 ,his first   
speculum mirror was five inches in      
diameter2 and1 while  it was in process 
of construction1 he was obliged to hold 
his hands on  it for sixteen hours at a 
stretch1 while his sister supplied his  
food  and read #8,the ,arabian ,nights1'
 #8,don ,quixote1' and other tales aloud
 to  him to pass the time4 ,at last1    
after two hundred failures1 he finished 

a  #e-;inch reflector1 and on ,march #d1
 #aggd1 he observed the ,orion nebula4  
,no  sooner had ,herschel commenced his 
celestial explorations than he  resolved
 to survey the entire heavens1 leaving  
no spot unvisited4    ,in #agge he      
commenced his review of the heavens1 but
 finding his  telescope inadequate he   
began the work of telescope-making      
afresh4  ,meanwhile he had much to      
distract him from astronomy4 ,in #aggf  
he became  director of the ,public      
,concerts at ,bath4 ,yet his enthusiasm 
was  unbounded3 he would run to his     
house between the acts at the theatre to
  observe the heavens4 ,in #aggi1 when  
observing the ,moon from the street in  
front of his house1 a gentleman asked   
permission to see the celestial         
wonders1 a request which ,herschel      
granted4 ,the gentleman1 ,dr ,watson of 
,bath1 introduced ,herschel to the      
,literary ,society1 and we find him in  
#aghj contributing two papers to the    
,royal ,society on ,mira ,ceti and the  

,moon4 ,in the same year he commenced   
his second review of the heavens1  and  
during its progress he made his first   
great discovery4 ,on ,march #ac1  #agha1
 while surveying the constellation      
,gemini1 he discovered a faint  object  
distinguished by a disc1 which he       
concluded to be a tailless  comet1 but  
which was soon shown to be a new planet 
beyond the orbit of  ,saturn4 ,this was 
the first planetary discovery made      
within the memory of  man4 ,king ,george
 ,,iii4 summoned ,herschel to ,london1  
and gave him a  pension of #bjj a-year1 
with the title of ,king's ,astronomer1  
pardoning  him also for his desertion   
from the army more than twenty years    
previously4 ,herschel then named the new
 planet the 8,georgium ,sidus10 a  title
 now abandoned and replaced by ,uranus4 
,william and ,caroline ,herschel now    
moved to ,datchet1 near ,windsor1 in    
#aghe to ,clay ,hall1 and finally1 in   
#aghf1 to ,slough1--8the spot of all the
  world10 said ,arago1 8where the       

greatest number of discoveries have been
  made40 ,here ,herschel and his sister 
worked for nearly forty years4 ,he      
communicated to the ,royal ,society     
paper after paper on astronomy in all   
its aspects4 ,he also continued the work
 of telescope-making1 and  constructed1 
in #aghi1 his #dj-;foot reflector1 the  
wonder of the age4 ,in  #aghg his sister
 was appointed his assistant1 and       
together the ,herschels  worked from    
dusk to dawn4 ,caroline ,herschel       
herself detected eight  comets and      
numerous nebul4 ,she relates in her     
memoirs that on one  occasion1 while she
 was acting as assistant1 the ink froze 
in her pen4  ,but such inconveniences   
mattered not to the ,herschels4 ,as     
,miss ,clerke  has well remarked1       
8,every serene dark night was to him a  
precious  opportunity1 availed of to the
 last minute4 ,the thermometer might    
descend below zero1 ink might freeze1   
mirrors might crack2 but1 provided  the 
stars shone1 he and his sister worked on

 from dusk to dawn4444 ,on  one occasion
 he is said to have worked without      
intermission at the  telescope and the  
desk for seventy-two hours40    ,honours
 were showered on ,herschel4 ,he was    
knighted in #ahaf1 and became           
,president of the ,royal ,astronomical  
,society in #ahbj1 besides receiving    
several honorary degrees4 ,but honours  
in no way elated him4 ,advancing  years 
in no way affected his wonderful mind4  
,but his duties as ,king's  ,astronomer 
necessitated his acting as 8showman of  
the heavens0 on the  visits of royalties
 to ,windsor1 often after a whole day's 
work1 when  rest was absolutely         
necessary4 ,this tremendous strain1     
which reflects  little credit on the    
,court1 proved too much for the old man4
 ,his health  began to give way1        
although his mind was as vigorous as    
ever4    ,herschel contributed his last 
paper to the ,royal ,society in #ahah1  
and  three years later sent a list of   
double stars to the new ,astronomical   

,society4 ,he made his last observation 
on ,june #a1 #ahba4 ,his strength had   
now left him1 and to this he could not  
reconcile himself4 ,as ,miss ,clerke    
puts it1 8,all his old instincts were   
still alive1 only the bodily power  to  
carry out their behests was gone4 ,an   
unparalleled career of  achievement left
 him unsatisfied with what he had       
done4444 ,his strong  nerves were at    
last shattered40 ,after a prolonged     
period of failing  health he died at    
,slough1 at the age of eighty-three1 on 
,august #be1  #ahbb4 ,on ,september #g  
he was buried in the church-yard of ,st 
,laurence at  ,upton4 ,on his tombstone 
are engraved the words--8,clorum        
perrupit  claustra0--he broke through   
the barriers of the skies4    ,the death
 of her brother was a terrible blow to  
,caroline ,herschel4  ,expecting to live
 only a twelvemonth1 she returned to    
,hanover to the  home of her brother1   
,dietrich ,herschel4 ,but she lived     
twenty-five years  among people who     

cared nothing for astronomy4 ,she was   
delighted at ,sir  ,john ,herschel's    
continuation of his father's work4 ,she 
compiled a  catalogue of all the        
clusters and nebul observed by her      
brother1 for  which she received the    
gold medal of the ,astronomical         
,society1 and she  was created an       
honorary member4 ,in #ahdf she received 
from the ,king of  ,prussia the gold    
medal of science4 ,but no honours made  
her in any way  elated4 ,she always held
 that whoever said much of her said too 
little of  her brother4 ,after a        
prolonged decline of health1 she died on
 ,january #i1  #ahdh1 aged ninety-seven 
years1 and was buried beside her father 
in the  churchyard of the               
,gartengemeinde at ,hanover1 leaving    
behind her a noble  example of          
self-sacrifice and devotion4            
,,chapter ,,ii4                         
,,herschel ,,the ,,discoverer4      ,one
 result of ,herschel's discoveries among
 the stars and nebul is that  his       

studies of the ,sun and planets1 with   
the exception of the discovery  of      
,uranus1 have been completely thrown    
into the shade4 ,nevertheless1 his  work
 in solar and planetary astronomy alone 
would have gained for him a  higher     
position in astronomy than his          
contemporaries4 ,the planets1           
satellites1 and comets were all         
attentively studied by the great        
astronomer2 indeed1 the scientific      
investigation of the surfaces of ,mars  
and ,saturn began with ,herschel4       
8,his attention to the ,sun10 ,miss     
,clerke truly remarks1 8might have been 
exclusive1 so diligent was his scrutiny 
of its shining surface40  ,sunspots were
 specially investigated by ,herschel1   
who closely studied  their              
peculiarities1 regarding them as        
depressions in the solar  atmosphere4   
,he also paid much attention to the     
facul1 but could not  observe them to   
the north and south of the ,sun1 thus   
proving their  connection with the spots

 which are confined to the regions north
 and  south of the equator4 8,there is  
all over the ,sun a great unevenness10  
said ,herschel1 8which has the          
appearance of a mixture of small points 
of  an unequal light2 but they are      
evidently a roughness of high and low   
parts40    ,herschel's solar            
observations were very valuable1 and did
 much for our  knowledge of the orb of  
day4 ,his theory of the ,sun's          
constitution--a  development of the     
hypothesis put forward by ,alexander    
,wilson  7#agad-aghf71 ,professor of    
,astronomy in ,glasgow--was1 however1   
very far  from the truth4 ,this was     
almost the only instance in which       
,herschel was  mistaken4 ,he regarded   
the ,sun as a cool1 dark globe1 8a very 
eminent1  large1 and lucid planet1      
evidently the first1 or1 in strictness  
of  speaking1 the only primary one of   
our system40 ,in his opinion an         
extensive atmosphere surrounded the     
,sun1 the upper stratum forming what    

,schrter named the 8photosphere40 ,this 
atmosphere1 estimated as two or  three  
thousand miles in depth1 was regarded as
 giving out light and  heat4 ,below this
 shining atmosphere there existed1      
,herschel believed1 a  region of clouds 
protecting the globe of the ,sun from   
the glowing  atmosphere1 and reflecting 
much of the light intercepted by them4  
,the  spots were believed to be openings
 in these atmospheres1 caused by the    
action of winds1 the umbra or dark      
portion of the spot thus representing   
the globe of the ,sun1 which ,herschel  
believed to be 8richly stored with      
inhabitants40 ,this theory held its     
ground for many years4 ,newton1 it is   
true1 believed the ,sun to be gaseous1  
but he propounded no hypothesis of  its 
constitution4 ,herschel's theory1 on the
 other hand1 was fully  developed1      
plausible1 and attractive4 ,it was held 
by eminent men of  science until #ahfj1 
when the revelations of the spectroscope
 showed it  to be quite untenable4 ,the 

theory was supported for many years by  
,sir  ,john ,herschel1 who1 however1    
abandoned it in #ahfd4 ,herschel made   
several  attempts to ascertain whether  
any connection existed between the state
  of the ,sun and the condition of the  
,earth4 ,in #ahja he was inclined to    
believe that 8some temporary defect of  
vegetation0 resulted from the  absence  
of sun-spots1 which1 he thought1 8may   
lead us to expect a  copious emission of
 heat1 and1 therefore1 mild seasons40   
,herschel  believed1 in fact1 that food 
became dear at the times of spot-minima4
 ,it  may be remarked that ,herschel    
never noted the spot-period of eleven   
years1 the discovery of which was       
afterwards made by ,schwabe4            
,herschel closely scrutinised the       
surfaces of the planets4 ,mercury alone 
was neglected by him4 ,from #aggg to    
#agic he observed ,venus1 with the      
object of determining the rotation      
period1 but he was unable to observe    
any markings on the surface of the      

planet4 ,he did not place reliance on   
,schrter's value of the rotation period 
7about twenty-three hours74  ,meanwhile1
 ,schrter announced the existence on    
,venus of mountains which  rose to five 
or six times the height of ,chimborazo4 
,as to these1 said  ,herschel1 8,i may  
venture to say that no eye which is not 
considerably  better than mine1 or      
assisted by much better instruments1    
will ever get  a sight of them40        
,herschel demonstrated the existence of 
an extensive  atmosphere round ,venus4  
8,the analogy between ,mars and the     
,earth10 ,herschel wrote in #aghc1 8is  
perhaps by far the greatest in the whole
 ,solar ,system40 ,in #aggg he  began1  
in his house at ,bath1 a series of      
observations on the red planet1  which  
yielded results of the utmost           
importance4 ,fixing his attention on    
the white spots at the north and south  
poles1--discovered by ,maraldi1  nephew 
of ,cassini1--he soon ascertained the   
fact that they waxed and  waned in size1

 the north polar cap shrinking during   
the summer of the  northern hemisphere1 
increasing in winter1 and vice versa in 
the  southern hemisphere4 ,he regarded  
the caps as masses of snow and ice      
deposited from 8a considerable1 though  
moderate1 atmosphere10 a theory  now    
generally accepted4 ,herschel gave an   
immense impetus to the study of  ,mars4 
,he carefully examined the planet's     
surface1 and the dark markings  were    
regarded by him as oceans4    ,during   
,herschel's lifetime the four small     
planets1 ,ceres1 ,pallas1 ,juno1  and   
,vesta1 were discovered by ,piazzi1     
,olbers1 and ,harding4 ,the great       
astronomer was much interested in these 
small worlds4 ,he commenced a  search   
through the ,zodiacal constellations for
 new planets1 but failed4  ,he was of   
opinion that many minor planets would be
 discovered4 ,accepting  ,olbers' theory
 of the disruption of a primitive       
planet1 ,herschel  calculated that      
,mercury might be broken up into #ce1jjj

 globes equal to  ,pallas4 ,meanwhile   
,herschel named the four new planets    
8,asteroids10 owing  to their minute    
size4 ,he estimated the diameter of     
,ceres at #afb miles  and ,pallas at    
#adg miles1 but ,professor ,barnard's   
measures have shown  them to be larger4 
,in connection with the discovery of the
 ,asteroids1 ,herschel showed a  very   
fine spirit4 ,in #8,the ,edinburgh      
,review' ,brougham declared that        
,herschel had devised the word          
8asteroid10 so that the discoveries of  
,piazzi and ,olbers might be kept on a  
lower level than his own discovery  of  
,uranus4 ,many scientists would have    
been much offended at this  contemptible
 insult1 but ,herschel merely remarked  
that he had incurred  8the illiberal    
criticism of #8,the ,edinburgh          
,review1'0 and that the  discovery of   
the ,asteroids 8added more to the       
ornament of our system  than the        
discovery of another planet could have  
done40    ,in ,herschel's time          

astronomers were acquainted with three  
of the outer  planets1--,jupiter1       
,saturn1 and ,uranus1--all of which were
 closely studied  by the great          
astronomer4 ,the belts of ,jupiter were 
supposed by him to be  analogous to the 
8trade-winds0 in the atmosphere of the  
,earth2 while the  drifting-spots on    
,jupiter's disc and their irregular     
movements were  carefully noted4 ,his   
observations on the four satellites of  
,jupiter led  him to believe that1 like 
our ,moon1 they rotated on their axes in
 a  period equal to that of their       
revolution round their primary--an      
opinion  shared by ,laplace1 and by many
 modern astronomers4    ,herschel's     
researches regarding ,saturn were1      
however1 much more  important than those
 on ,jupiter4 ,the globe of the planet1 
the rings and  the satellites1 were     
favourite objects of study at ,bath and 
,slough4 ,in  #agid he perceived a spot 
on the surface of ,saturn1 and made the 
first  determination of the rotation of 

the planet1 which he fixed as #aj hours 
#af minutes1--a result confirmed by     
modern astronomers4 ,the rings were     
subjected to the closest scrutiny4      
,herschel believed them to be solid1    
and he also considered them to revolve  
round ,saturn in about #aj hours4  ,it  
appears that he observed the famous     
8dusky ring10 but supposed it to  be a  
belt on the surface of the planet4 ,he  
also studied ,cassini's  division in the
 ring1 ascertaining its reality4    ,on 
completing his famous #dj-;foot         
reflector1 ,herschel1 on ,august #bh1   
#aghi1 turned it on ,saturn and its five
 known satellites4 ,near the  planet1   
and in the plane of the ring1 was seen  
another object1 which  ,herschel        
believed to be a sixth satellite4 ,to   
settle the question1 he  watched the    
planet for several hours to see if the  
object would partake  in the planet's   
motion4 ,finding that it did1 he        
announced it as a new  satellite1 which 
he found to revolve round ,saturn in #a 

day #h hours4  ,about three weeks later1
 on ,september #ag1 ,herschel discovered
 another  satellite yet closer to       
,saturn1 revolving round the planet in  
about #bb  hours4 ,these two satellites 
were not seen by any astronomers except 
,herschel2 and after his death they     
could not be observed4 ,his son1        
however1 rediscovered them4    ,the     
eighth satellite1 ,japetus1 was shown by
 ,herschel to rotate on its  axis in a  
period equal to that of its revolution1 
and his observations  were confirmed by 
modern observers4 8,i cannot10 ,herschel
 said1 8help  reflecting with some      
pleasure on the discovery of an analogy 
which shows  that a certain uniform plan
 is carried on among the secondaries of 
our  ,solar ,system2 and we may         
conjecture that probably most of the    
satellites  are governed by the same    
law40 ,in ,april #ahje ,herschel        
observed the globe  of ,saturn to       
present not a spherical but a           
8square-shouldered0 aspect4  ,it was for

 long believed that this was an optical 
illusion2 but ,proctor  and others have 
shown that it is quite possible for     
storms in ,saturn's  atmosphere to cause
 the planet's apparent distortion in    
shape4    ,herschel paid much attention 
to the planet ,uranus1 which he         
discovered  on ,march #ac1 #agha4 ,the  
discovery of ,uranus1 which was         
mentioned in a  previous chapter1 was in
 a sense the most striking of           
,herschel's  achievements4 ,uranus was  
the first planet discovered within the  
memory  of man3 besides1 the discovery  
enlarged the diameter of the ,solar     
,system  from #hhf to #aggb millions of 
miles4 ,throughout his lifetime         
,herschel  referred to the planet as the
 8,georgium ,sidus10 out of gratitude to
  ,george ,,iii4 for appointing him     
,king's ,astronomer2 but the astronomers
 of  ,france and ,germany1 who1 as ,sir 
,robert ,ball remarks1 8saw no reason   
why  the ,king of ,england should be    
associated with ,jupiter and ,saturn10  

opposed this term4 ,lalande called the  
planet 8,herschel10 but ,herschel's     
countrymen1 the ,germans1 named it      
,uranus1 in keeping with the custom of  
designating the planets from the ,greek 
mythology4 ,the name of ,uranus         
ultimately prevailed4    ,in ,january   
#aghg ,herschel discovered two          
satellites to ,uranus1 with the  aid of 
his #bj-;foot telescope4 ,these         
satellites he believed to revolve  round
 ,uranus in #h days and #ac days        
respectively1 and accordingly he made  a
 drawing of what their positions should 
be on ,february #aj4 ,on that day  he   
found them in their predicted places4   
,in #agig he announced that the         
satellites revolved round ,uranus in    
orbits at right angles to the  ecliptic1
 and in a retrograde direction4 ,in     
subsequent years ,herschel  believed    
that he had discovered other four       
satellites to ,uranus1 but he  was      
unable to confirm his belief4 ,as ,mr   
,gore says1 some of the  satellites     

8must1 therefore1 have been either      
optical #8ghosts' or else  small fixed  
stars which happened to be near the     
planet's path at the  time of           
observation4 ,herschel also suspected   
that he could see traces of  rings round
 ,uranus like those round ,saturn1 but  
his observation was  never confirmed1   
either by himself or other observers40  
,although ,herschel made several        
important observations on the ,moon1 and
  measured the heights of the lunar     
mountains1 he was not a devoted  student
 of our satellite4 ,caroline ,herschel  
remarks in her memoirs that  if it had  
not been for clouds or moonlight1       
neither her brother nor  herself would  
have got any sleep2 adding that         
,herschel on the moonlight  nights      
prepared his papers or made visits to   
,london4 ,however1 he did  make some    
investigations1 and in #aghc and #aghg  
believed himself to have  witnessed the 
eruption of three lunar volcanoes4 ,he  
afterwards  concluded1 however1 that    

what he believed to be eruptions was    
really the  reflexion of earth-shine    
from the white peaks of the lunar       
mountains4  ,herschel never discovered a
 comet1 leaving that branch of astronomy
 to  his sister1 who discovered eight of
 these objects4 ,he was1 however1 much  
interested in comets1 and attentively   
studied them1 introducing the  terms of 
8head10 8nucleus10 and 8coma40 ,herschel
 anticipated the view  that comets are  
not lasting1 but are partly             
disintegrated at their  perihelion      
passages4 ,he was of opinion that they  
travelled from star to  star4 ,the      
extent of their tails and appendages he 
thought to be a test  of their age4     
,we have now completed our sketch of    
,herschel's important labours  regarding
 our ,solar ,system4 ,as ,miss ,clerke  
says1 8,a whole cycle of  discoveries   
and successful investigations began and 
ended with him40 ,but  through observing
 the stars he made a further discovery  
in connection  with the ,solar ,system2 

indeed1 one of the greatest discoveries 
in the  history of astronomy--the       
movement through space of the ,sun1     
carrying  with it planets and comets4   
8,if the proper motion of the stars be  
admitted10 said ,herschel1 8who can     
deny that of our ,sun80 ,of course it   
was plain that the motion of the ,sun   
could only be detected through the      
resulting apparent motion of the  stars4
 ,thus1 if the ,sun is moving in a      
certain direction1 the stars in  front  
will appear to open out1 while those    
behind will close up4 ,but the  problem 
is by no means so easy as this4 ,the    
stars are also in motion1  and1 before  
the solar motion can be discovered1 the 
proper motions of  the stars--themselves
 very minute--have to be decomposed into
 two parts1  the real motion of the     
star1 and the apparent motion1 resulting
 from the  movement of the ,solar       
,system4 ,to any astronomer but         
,herschel the problem  would have been  
insoluble4 ,only sixty years had elapsed

 since ,halley had  announced the proper
 motions of the brighter stars which had
 been  previously supposed to be        
immovable--hence the name of 8fixed     
stars40  ,herschel did not deal with the
 motions of many stars4 ,only a few     
proper  motions were known with accuracy
 when he attacked the problem in #aghc4 
,making use of the proper motions of    
seven stars1 and separating the real    
from the apparent motion1 he found that 
the ,solar ,system was moving  towards a
 point in the constellation ,hercules1  
the 8apex0 being marked  by the star    
,herculis4 ,the rate of the solar       
motion1 ,herschel thought1  was         
8certainly not less than that which the 
,earth has in her annual  orbit40 ,this 
extraordinary discovery was one of      
,herschel's greatest  works4 8,its      
directness and apparent artlessness10   
,miss ,clerke remarks1  8strike us dumb 
with wonder40 ,in #ahje ,herschel again 
attacked the  subject1 utilising the    
proper motions of thirty-six stars4 ,his

 second  inquiry1 on the whole1         
confirmed his previous result1 the      
8apex0 being  again situated in         
,hercules2 but the determination of     
#aghc was probably  the more accurate of
 the two4    ,herschel was far in       
advance of his time regarding the solar 
motion4 ,the  two greatest astronomers  
of the next generation1 ,bessel and ,sir
 ,john  ,herschel1 rejected the results 
reached by ,sir ,william ,herschel4 ,but
 in  #ahcg ,argelander1 after a profound
 mathematical discussion1 confirmed     
,herschel's views1 and proved the solar 
motion to be a reality4 ,since  that    
date the problem has been attacked by   
various methods by ,otto  ,struve1      
,gauss1 ,mdler1 ,airy1 ,dunkin1 ,ludwig 
,struve1 ,newcomb1 ,kapteyn1  ,campbell1
 and others1 with the result that the   
reality of the solar  motion and of the 
direction fixed by ,herschel has been   
proved beyond a  doubt4 ,as ,sir ,robert
 ,ball well remarks1 mathematicians have
 exhausted  every refinement1 8but only 

to confirm the truth of that splendid   
theory  which seems to have been one of 
the flashes of ,herschel's genius40     
,in his volume #8,herschel and his      
,work1' ,mr ,james ,sime writes3 8,to   
,herschel belongs the credit not merely 
of having suspected the  revolution of  
sun around sun in the far-distant realms
 of space1 but  also of actually        
detecting that this was going on among  
the stars40  ,throughout his career     
double stars were favourite objects of  
observation4 ,the study of double stars 
was commenced by ,herschel while a      
musician in ,bath4 ,before his day1 of  
course1 double stars had been           
discovered and studied1 but it was      
believed that the proximity of two      
stars was merely an optical accident1   
the brighter star being much  nearer to 
us than the other4 ,herschel1 at first  
sharing the general  view1 observed     
double stars in the hope of measuring   
their relative  parallaxes2 assuming one
 star to be much farther away from the  

,solar  ,system than another1 he        
attempted to measure the parallactic    
displacement of the brighter star       
relatively to the position of the       
fainter4 8,this10 he afterwards wrote1  
8introduced a new series of             
observations4 ,i resolved to examine    
every star in the heavens with the      
utmost attention1 that ,i might fix my  
observations upon those that would  best
 answer my end4 ,i took some pains to   
find out what double stars had  been    
recorded by astronomers2 but my         
situation permitted me not to  consult  
extensive libraries1 nor1 indeed1 was it
 very material2 for as ,i  intended to  
view the heavens myself1 ,nature1 that  
great volume1 appeared  to me to contain
 the best catalogue40    ,herschel1 on  
,january #aj1 #aghb1 submitted to the   
,royal ,society a  catalogue of #bfi    
double stars3 of these he himself       
discovered #bbg4 ,in  ,december #aghd he
 forwarded another catalogue1 containing
 #dcd stars4 ,he  soon found that he was

 unable to measure stellar parallax1 and
 the idea  dawned on him that the double
 stars were physically connected by the 
law  of gravitation1 though he made no  
announcement to that effect for many    
years4 ,on ,july #a1 #ahjb1 ,herschel   
informed the ,royal ,society that       
8casual  situations will not account for
 the multiplied phenomena of double     
stars4444 ,i shall soon communicate a   
series of observations1 proving  that   
many of them have already changed their 
situation in a progressive  course1     
denoting a periodical revolution round  
each other40 ,in #ahjc he  showed that  
many stars were revolving round their   
centres of gravity1  proving them1 in   
his own words1 to be 8intimately held   
together by the  bond of mutual         
attraction40 ,in other words1 ,herschel 
discovered that the  law of gravitation 
prevailed in the ,stellar ,universe1 as 
well as in our  ,solar ,system--that the
 law which ,newton ascertained to       
prevail in the  ,solar ,system extended 

throughout the depth of space4          
,herschel did not merely prove the      
revolution of the binary stars2 he      
assigned periods to those which he had  
particularly studied4 ,he believed  the 
period of ,castor to be #cdb years2     
,leonis #abjj years2  ,serpentis  #cge  
years2 and  ,botis #afha years4         
,herschel did not compute the orbits    
mathematically4 ,this was not done for  
nearly thirty years1 when the           
calculation of binary star-orbits was   
commenced by ,savary1 ,sir ,john        
,herschel1 and ,encke4    ,in #aghb the 
,french astronomer1 ,charles ,messier   
7#agcj-ahag71 published  a list of #ajc 
nebul4 ,in the following year ,herschel 
commenced his  famous sweeps of the     
heavens with his large reflectors1 and  
during these  he made many remarkable   
discoveries4 ,in #aghf he published in  
the  #8,philosophical ,transactions' of 
the ,royal ,society a catalogue of a    
thousand new nebul and star-clusters1 in
 which he gave the position of  each    

object with a short description of its  
appearance1 written by  ,caroline       
,herschel while her brother actually had
 the object before his  eyes4 ,in #aghf 
,herschel published a catalogue of      
another thousand  clusters and nebul1   
followed in #ahjb by a list of #ejj2    
making a total  of #bejj clusters and   
nebul discovered by the great           
astronomer4 ,this  alone would have     
gained a great name for ,william        
,herschel in this branch  of astronomy4 
,in the space of only twenty years #bejj
 nebul and clusters  had been           
discovered4 ,the various nebul and      
clusters were divided into  eight       
classes1 as follows3 the first class    
being 8bright nebul10 the  second 8faint
 nebul10 the third 8very faint nebul10  
the fourth  8planetary nebul10 so named 
by ,herschel from their resemblance to  
planetary discs1 the fifth class        
contained 8very large nebul10 the  sixth
 8very compressed and rich clusters of  
stars10 the seventh 8pretty  much       

compressed clusters of large or small   
stars10 and the eighth  8coarsely       
scattered clusters of stars40    ,at    
first ,herschel believed all nebul to be
 clusters of stars1 the  irresolvable   
nebul being supposed to be farther from 
our system than  the resolvable nebul4  
,as many of the nebul which ,messier    
could not  resolve had yielded to       
,herschel's instruments1 ,herschel      
believed that  increase of telescopic   
power would resolve the hazy spots of   
light which  remained nebulous4 ,in the 
paper of #aghe1 in which ,herschel dealt
 with  the construction of the heavens1 
he stated his belief that many of the   
nebul were external galaxies--universes 
beyond the ,milky ,way2 and in  #aghf he
 remarked that he had discovered fifteen
 hundred universes6    ,arago1 ,mitchel1
 ,nichol1 ,chambers1 and other writers  
quite misinterpreted  ,herschel's views 
on the nebul when they said that he     
believed them to  be all external       
galaxies4 ,in #aghe ,herschel believed  

many to be connected  with the sidereal 
system2 considering that in some parts  
of the ,galaxy  8the stars are now      
drawing towards various secondary       
centres1 and will  in time separate into
 different clusters40 ,he was coming to 
the view  that the star-clusters were   
secondary aggregations within the       
,galaxy1  probably the true theory4 ,he 
pointed out that in ,scorpio1 the       
cluster  ,messier #hj is bounded by a   
black chasm1 four degrees wide1 from    
which he  believed the stars had been   
drawn in the course of time to form the 
cluster4 ,his sister records that one   
night1 after a 8long1 awful  silence10  
he exclaimed on coming on this          
chasm--8,hier ist wahrhaftig ein  ,loch 
im ,himmel60 7,here1 truly1 is a hole in
 the heavens47    ,herschel was now     
gradually giving up his theory of       
external galaxies and  his 8disc-theory0
 of the ,universe2 but he still believed
 even the  nebulous objects to be       
irresolvable only through immensity of  

distance4  ,in #agia1 however1 he drew  
attention to a remarkable star in       
,taurus1  surrounded by a nebulous      
atmosphere1 regarding which he wrote1   
8,view1  for instance1 the nineteenth   
cluster of my sixth class1 and          
afterwards  cast your eye on this cloudy
 star4 ,our judgment1 ,i will venture to
 say1  will be that the nebulosity about
 the star is not of a starry  nature4   
,we therefore either have a central body
 which is not a star1  or have a star   
which is involved in a shining fluid1 of
 a nature totally  unknown to us40 ,and 
with caution he added that 8the envelope
 of a cloudy  star is more fit to       
produce a star by its condensation than 
to depend  upon the star for its        
existence40    ,this was written in     
#agia1 five years before ,laplace       
propounded his  nebular theory4         
,meanwhile ,herschel1 believing that    
8these nebulous stars  may serve as a   
clue to unravel other mysterious        
phenomena10 found that  the theory of a 

8shining fluid0 would suit the          
appearance of the  irresolvable         
planetary nebul and the great nebula in 
,orion much better  than the extravagant
 idea of 8external universes40 ,herschel
 now  considered the ,orion nebula to be
 much nearer to the ,solar ,system than 
he formerly did1 and ceased to regard it
 as external to the ,galaxy4 ,for       
twenty years ,herschel patiently        
observed the nebul1 and it was not      
until #ahaa that he propounded his      
nebular hypothesis of the evolution of  
the ,sun and stars4 ,he found the       
gaseous matter in all stages of         
condensation1 from the diffused cloudy  
nebul like that in ,orion1  through the 
planetary nebula and the regular nebula1
 to the perfect  stars1 like ,sirius and
 the ,sun4 ,herschel's nebular theory   
was a grand  conception1 and a          
magnificent attack on the secrets of    
nature4    ,sir ,robert ,ball says3     
8,not from abstract speculation like    
,kant1 nor from  mathematical suggestion

 like ,laplace1 but from accurate and   
laborious  study of the heavens1 was the
 great ,william ,herschel led to the    
conception of the nebular theory of     
evolution40 ,herschel's nebular  theory 
was wider and less rigorous than that of
 ,laplace4 ,laplace reached  his theory 
by reasoning backwards2 ,herschel by    
observing the nebul in  process of      
condensation4 ,consequently1 while      
,laplace's theory has  required         
modification1 ,herschel's1 from its     
width1 is universally  accepted1 because
 there is nothing mathematically        
rigorous in it4 ,the  great ,german did 
not go into details like his ,french    
contemporary4 ,he  sketched the         
evolution of the stars in a wider sense4
    ,the astronomer's 8#aejj universes10
 ,miss ,clerke remarks1 8had now        
logically ceased to exist40 ,herschel   
had gathered much evidence about        
nebular distribution which shattered his
 belief in external universes1  although
 he still thought in #ahah that some    

galaxies were included among  the       
non-gaseous nebul4 ,in #aghd ,herschel  
pointed out that the clusters  and nebul
 8are arranged to run in strata02 and   
some time later he found  that the nebul
 were aggregated near the galactic      
poles2 in other words1  where nebul are 
numerous1 stars are scarce1 and vice    
versa4 ,so  rigorously did this rule    
hold1 that when dictating his           
observations to  his sister ,caroline1  
he would1 on noting a paucity of stars1 
warn her to  8prepare for nebul40    8,a
 knowledge of the construction of the   
heavens has always been the  ultimate   
object of my observations40 ,so         
,herschel wrote in #ahaa4 ,all his      
investigations were secondary to the    
problem which was constantly before  his
 mind--the extent and structure of the  
,universe4 ,he aspired to be the        
,copernicus of the ,sidereal ,system4   
,although ,bruno1 ,kepler1 ,wright1     
,kant1  and ,lambert had speculated     
regarding the construction of the       

heavens1  they had not the slightest    
evidence on which to base their ideas4  
,there  was no science of sidereal      
astronomy4 ,the stars were observed only
 to  assist navigation1 and the primary 
object of star-catalogues was to        
further knowledge of the motions of the 
planets4 ,in ,herschel's day1  also1 the
 distances of the stars had not been    
measured1 and he had to  base his views 
on the distribution of the stars4 ,in   
#aghd1 therefore1 he  commenced a survey
 of the heavens1 in order to ascertain  
the number of  stars in various parts of
 the sky4 ,this method1 which he named  
8star-gauging10 consisted in counting   
the number of stars in the  telescopic  
field4 ,totally he secured #cdjj gauges4
 ,his studies showed  that in the region
 of the ,galaxy the stars were much more
 numerous than  near the galactic poles4
 ,sometimes he saw as many as #ehh stars
 in a  telescopic field1 at other times 
only #b4 ,he remarked that he had 8often
  known more than #ej1jjj pass before   

his sight within an hour40 ,assuming    
that the stars were1 on the average1 of 
about the same size1 and  scattered     
through space with some approach to     
uniformity1 ,herschel was  able to      
compute the extent to which his         
telescope penetrated into space2  and1  
assuming that the ,universe was finite  
and that his  8gauging-telescope0 was   
sufficiently powerful to completely     
resolve the  ,milky ,way1 he was enabled
 to sketch the shape and extent of the  
,universe4    ,thus ,herschel concluded 
that the ,universe extended in the      
direction of  the ,galaxy to #hej times 
the mean distance of stars of the first 
magnitude4 ,in the direction of the     
galactic poles the thickness was only   
#aee times the distance of stars of the 
same magnitude4 ,herschel was thus      
enabled to sketch the probable form of  
the ,universe1 which he regarded  as    
cloven at one of its extremities1 the   
cleft being represented by the  famous  
gap in the ,milky ,way4 ,the ,universe  

was1 in fact1 supposed to be a  cloven  
disc1 and the ,milky ,way was merely a  
vastly extended portion of  it and not a
 region of actual clustering4 ,on this  
theory the clusters  and nebul were     
supposed to be galaxies external to the 
,universe4 ,even  in #aghe1 however1    
,herschel believed that there were      
regions in the ,milky  ,way where the   
stars were more closely clustered than  
others4 8,it would  not be difficult10  
he wrote in #aghe1 8to point out two or 
three hundred  gathering clusters in our
 system40    ,strange to say1           
,herschel's original ideas regarding the
 ,universe were  accepted for many years
 by astronomical writers4 ,arago        
accepted  ,herschel's original theory1  
unaware that he had in reality abandoned
 it1  and he was followed by a host of  
,french and ,english writers who did not
  take the trouble to read each of      
,herschel's papers1 merely quoting that 
of #aghe1 and believing that it         
represented his final ideas on the      

subject4 ,even ,sir ,john ,herschel     
seems to have been unaware that his     
father gave up the disc theory of the   
,universe4 ,the famous ,german          
astronomer1 ,wilhelm ,struve1 after an  
exhaustive study of ,herschel's  papers1
 was enabled to prove in #ahdg that the 
theory had been abandoned  by ,herschel2
 and in ,england the late ,r4 ,a4       
,proctor independently  demonstrated the
 same thing4 ,meanwhile1 supposing      
,herschel had not given  up his theory1 
it would be quite untenable4 ,after     
considering the fact  that the brighter 
stars1 down to the ninth magnitude1     
aggregate on the  ,milky ,way1 ,mr ,gore
 says3 8,as the stars are by hypothesis 
supposed to be  uniformly distributed   
throughout every part of the disc1 and  
as the  limiting circles for stars to   
the eighth and ninth magnitudes fall    
well  within the thickness of the disc1 
there is no reason why stars of these   
magnitudes should not be quite as       
numerous in the direction of the        

galactic poles as in that of the ,milky 
,way itself4 ,we see1 therefore1  that  
the disc theory fails to represent the  
observed facts1 and that  ,struve and   
,proctor were amply justified in their  
opinion that the theory  is wholly      
untenable1 and should be abandoned40    
,the observations made by ,herschel     
himself eventually proved fatal to the  
disc theory--a hypothesis which he had  
all along held very lightly4 ,his  ideas
 about subordinate clusters within the  
,milky ,way were soon  confirmed1 and   
though in #agii he still adhered to the 
disc theory1 he  wrote in #ahjb1 8,i am 
now convinced1 by a long inspection and 
continued  examination of it1 that the  
,milky ,way itself consists of stars    
very  differently scattered from those  
which are immediately about us4 ,this   
immense starry aggregation is by no     
means uniform4 ,the stars of which it   
is composed are very unequally          
scattered0--a conclusion quite opposed  
to  the disc theory1 where the ,milky   

,way was supposed to be merely an       
extended portion of the ,universe4      
,in #ahaa ,herschel wrote as follows3   
8,i must freely confess that by         
continuing my sweeps of the heavens1 my 
opinion of the arrangement of  the      
stars1 and their magnitudes1 and some   
other particulars1 has  undergone a     
gradual change2 and1 indeed1 when the   
novelty of the subject  is considered we
 cannot be surprised that many things   
formerly taken for  granted should on   
examination prove to be different from  
what they were  generally but           
incautiously supposed to be4 ,for       
instance1 an equal  scattering of the   
stars may be admitted in certain        
calculations2 but  when we examine the  
,milky ,way1 or the closely compressed  
clusters of  stars1 of which my         
catalogues have recorded so many        
instances1 this  supposed equality of   
scattering must be given up40    ,this  
was the virtual abandonment of the disc 
theory4 ,six years later  ,herschel     

announced that in six cases he had      
failed to resolve the ,milky  ,way1     
stating that his telescopes could not   
fathom it4 ,this was the  abandonment of
 his second assumption--namely1 that his
 telescope was  sufficiently powerful to
 penetrate to the limits of the         
,universe4 ,yet he  still thought that  
some of the star-clusters might be      
external galaxies1  although he could   
not even dogmatically assert our        
,universe to be  limited4 ,in an error  
of translation1 ,struve left the        
impression that  ,herschel believed our 
,universe to be unfathomable or         
infinite1 and was  obliged to devise a  
most artificial theory of the extinction
 of light to  account for the fact that 
the sky did not shine with the          
brilliance of  the ,sun1 which it would 
do were the stars infinite in number4   
,of course1  ,herschel did not actually 
believe the ,universe to be infinite1   
and1 had  he lived1 he would probably   
have shown that all the star-clusters   

which  we see are included within the   
bounds of our finite ,galaxy4    ,in    
#ahad ,herschel was 8still engaged in a 
series of observations for  ascertaining
 a scale whereby the extent of the      
,universe1 as far as it is  possible for
 us to penetrate into space1 may be     
fathomed40 ,in #ahag he  described      
another method of star-gauging1 which   
,arago and other writers  have confused 
with that which he devised in #aghe4    
,the two methods1  however1 were quite  
distinct from each other4 ,in the first 
system1 one  telescope was used on      
different regions of the heavens2       
whereas in the  second method1 various  
telescopes were used on identical       
regions4 ,the  principle was that the   
telescopic power necessary to resolve   
groups of  stars indicates the distance 
at which the stars of the groups lie4   
,this1  however1 also assumed an equal  
distribution of stars1 and as the late  
,mr  ,proctor says1 8,i conceive that no
 question can exist that the principle  

is unsound1 and that ,herschel would    
himself have abandoned it had he  tested
 it earlier in his observing career4444 
,in applying it1 ,sir ,w4  ,herschel    
found regions of the heavens very       
limited in extent1 where the  brighter  
stars 7clustered like the fainter7 were 
easily resolved with  low powers1 but   
where his largest telescopes could not  
resolve the  faintest4 ,these regions1  
if the principle were true1 must be     
long1  spike-shaped star groups1 whose  
length is directed exactly towards the  
astronomer on ,earth1--an utterly       
incredible arrangement40    ,herschel1  
at the time of his death1 left unsolved 
the problem of the  construction of the 
heavens4 ,it is still unsolved1 and will
 doubtless  remain so until astronomers 
know more about the distances and       
motions of  the stars4 ,his last        
observation of the ,galaxy showed that  
even with his  #dj-;foot reflector he   
could not fathom it4 ,consequently1 as  
we have  mentioned1 ,struve and his     

successors regarded the ,universe as    
infinite--a  theory which has now       
received its death-blow4 ,herschel was  
undoubtedly  correct when he stated his 
belief in a limited ,universe4          
,herschel's star-gauges1 and those of   
his son1 still remain of immense  value 
to astronomers in any discussion of the 
construction of the  heavens4 ,thus1    
although they failed to reveal to       
,herschel the structure  of the         
,universe1 they have been of much use to
 his successors4  ,herschel's discussion
 of the supreme problem--the ultimate   
object of his  observations--constitutes
 one of the most interesting chapters in
 the  history of science1 and marks a   
new era in human thought4 ,in the words 
of ,miss ,clerke3 8,one cannot reflect  
without amazement that the special      
life-task set himself by this struggling
 musician--originally a penniless       
deserter from the ,hanoverian           
,guard--was nothing less than to search 
out  the #8construction of the heavens4'

 ,he did not accomplish it1 for that    
was impossible2 but he never            
relinquished1 and1 in grappling with it1
  laid deep and sure the foundations of 
sidereal science40                      
,,chapter ,,iii4                        
,,the ,,sun4      ,four years after the 
death of ,herschel1 an apothecary in the
 little  ,german town of ,dessau        
procured a small telescope1 with which  
he began to  observe the ,sun4 ,the name
 of this apothecary was ,samuel         
,heinrich  ,schwabe 7#aghi-ahge74 ,in   
#ahbf he commenced to observe the spots 
on the  ,sun's disc1 counting them from 
day to day1 more for self-amusement than
  from any hope of discovery2 for       
previous astronomers had agreed that no 
law regulated the number of the         
sun-spots4 ,every clear day ,schwabe    
pointed his telescope at the ,sun and   
took his record of the spots2 this  he  
continued for forty-three years1 until  
within a few years of his  death on     
,april #aa1 #ahge4 ,as early as #ahdc   

,schwabe hinted that a possible  period 
of ten years regulated the distribution 
of the spots on the ,sun1  but no       
attention was given to his idea4 ,in    
#ahea1 however1 the result of  his      
twenty-six years of observation was     
published in ,humboldt's  #8,cosmos1'   
and ,schwabe was able to show that the  
spots increased and  decreased in a     
period of about ten years4 ,astronomers 
at once recognised  the importance of   
,schwabe's work1 and in #aheg he was    
rewarded by the  ,gold ,medal of the    
,royal ,astronomical ,society of        
,london4    ,rudolf ,wolf 7#ahac-ahib7  
of the ,zrich ,observatory now undertook
 to  search through the records of      
sun-spot observation1 from the days of  
,galileo and ,scheiner1 to find traces  
of the solar cycle discovered by        
,schwabe4 ,he was successful1 and was   
enabled to correct ,schwabe's  estimate 
of the length of the period1 fixing it  
as on the average #aaaa  years4         
,additional interest1 however1 was given

 to ,schwabe's and ,wolf's              
investigations by the remarkable        
discoveries which followed4 ,in         
,september #ahea ,john ,lamont          
7#ahje-ahgi71 a ,scottish               
astronomer1--born at  ,braemar in       
,aberdeenshire1 but employed as director
 of the ,munich  ,observatory1--after   
searching through the magnetic records  
collected at  ,gttingen and ,munich1    
discovered that the magnetic variations 
indicated  a period of #aj years4 ,soon 
after this ,sir ,edward ,sabine         
7#aghh-ahhc71  the ,english physicist1  
from a discussion of an entirely        
different set of  observations1         
independently demonstrated the same     
thing1 proving  conclusively that once  
in about ten years magnetic disturbances
 reached  their height of violence2 and 
,sabine was not slow to notice the      
correspondence between the magnetic     
period and the sun-spot period4 ,in  the
 same year 7#aheb7 ,wolf and ,alfred    
,gautier 7#agic-ahha7 independently     

made the same discovery1 which had thus 
been made by four separate              
investigators4    ,in the same year an  
,english amateur astronomer1 ,richard   
,christopher  ,carrington 7#ahbf-ahge71 
commenced a series of solar observations
 which  led to some remarkable          
discoveries4 ,from observations on the  
spots1  ,carrington discovered that     
while the ,sun's rotation was performed 
in #be  days at the equator1 it was     
protracted to #bg days midway between   
the  equator and the poles4 ,in #aheh   
,carrington demonstrated the fact that  
spots are scarce in the vicinity of the 
solar equator1 but are confined  to two 
zones on either side1 becoming scarce   
again at thirty-five  degrees north or  
south of the equator4 ,contemporary with
 ,carrington was  ,friedrich ,wilhelm   
,gustav ,sprer 7#ahbb-ahie71 who was    
born in ,berlin in  #ahbb and died at   
,giessen1 ,july #g1 #ahie4 ,he commenced
 his solar  observations about the same 
time as ,carrington1 and independently  

discovered the ,sun's equatorial        
acceleration4 ,from observations at his 
little private observatory at ,anclam in
 ,pomerania1 continued at the           
,astrophysical ,observatory in ,potsdam1
 ,sprer demonstrated a remarkable  law  
regarding sun-spots4 ,this law is thus  
described by a well-known  astronomer3  
8,the disturbance which produces the    
spots of a given  sun-spot period first 
manifests itself in two belts about     
thirty degrees  north and south of the  
,sun's equator4 ,these belts then draw  
in toward  the equator1 and the sun-spot
 maximum occurs when their latitude is  
about sixteen degrees2 while the        
disturbance gradually and finally dies  
out at a latitude of eight or ten       
degrees4 ,two or three years before     
this disappearance1 however1 two new    
zones of disturbance show  themselves4  
,thus1 at the sun-spot minimum there are
 four well-marked  spot-belts1--two near
 the equator1 due to the expiring       
disturbance1 and  two in high latitudes1

 due to the newly beginning outbreak40  
,these  remarkable discoveries1 which   
resulted from the investigations of     
,schwabe1 ,carrington1 and ,sporer1 are 
a brilliant example of what may be  done
 by amateurs in astronomy4    ,at the   
time when ,carrington and ,sprer were   
pursuing these researches1  the         
spectroscope came into use as an        
astronomical instrument1 and since      
#ahei solar astronomy has been almost   
entirely spectroscopic4 ,before we  can 
rightly understand the principles of    
spectroscopic astronomy1 we  must go    
back to the life and work of its        
founder--,joseph von ,fraunhofer4       
,the son of a poor glazier1 ,joseph von 
,fraunhofer was born on ,march #f1      
#aghg1 at ,straubing1 in ,bavaria4 ,his 
father and mother having died when      
their son was quite young1 the boy1 on  
account of his poverty1 was  apprenticed
 to a looking-glass manufacturer in     
,munich named  ,weichselberger1 who     
acted tyrannically1 keeping him all day 

at hard  work4 ,still the lad borrowed  
some old books1 and spent his nights in 
study4 ,young ,fraunhofer lodged in an  
old tenement in ,munich1 which on  ,july
 #ba1 #ahja1 collapsed1 burying in its  
ruins its occupants4 ,all were  killed  
but ,fraunhofer1 who1 though seriously  
injured1 was dug out from  the ruins    
four hours later4 ,the distressing      
accident was witnessed by  ,prince      
,maximilian ,joseph1 ,elector of        
,bavaria4 ,he became interested in      
,fraunhofer1 and presented him with a   
sum of money4 ,of this he made good     
use4 ,he was already interested in      
optics1 and he bought some books on     
that subject1 as well as a              
glass-polishing machine4 ,the remainder 
of the  money served to procure his     
release from his tyrannical master1     
,weichselberger4    ,fraunhofer became  
acquainted with prominent scientists at 
,munich1 who  provided him with books on
 optics and mathematics4 ,meanwhile the 
young  optician occupied his time in    

shaping and finishing lenses4 ,in #ahjf 
he  entered the optical department of   
the ,optical and ,physical ,institute of
  ,munich1 and the following year1 when 
only twenty years of age1 was  appointed
 to the chief post in that department4  
,in #ahad he commenced his              
investigations with the prism1 which    
have made his name famous4    ,newton   
had found that1 in passing through a    
prism1 white light is  dispersed into   
its primary colours1 making up the band 
of coloured light  known as the solar   
spectrum4 ,but he failed to recognise   
the existence of  dark lines in the     
spectrum4 ,casually seen in #ahjb by    
,william ,hyde  ,wollaston 7#aghf-ahbh71
 an ,english physicist1 these lines were
 first  thoroughly examined by          
,fraunhofer4 ,allowing light from the   
,sun to pass  through a prism attached  
to the telescope1 he was amazed to find 
several  dark lines in the spectrum4 ,by
 the year #ahad he had detected no less 
than #cjj or #djj of these lines4       

,fraunhofer named the more prominent    
lines by the letters of the alphabet1   
from ,a in the red to ,h in the  violet4
 ,they are now known as the ,fraunhofer 
lines4 ,at first he was much  perplexed 
regarding the nature of the dark lines4 
,he suspected that they  might be an    
optical effect1 depending on the quality
 of the glass used1  and he tried       
different prisms1 but the lines were    
still to be seen4 ,then  he turned his  
prism to bright clouds to see if they   
were visible in  reflected sunlight1 and
 he found that they were4 ,he examined  
the ,moon  and again perceived them1 as 
moonlight is merely reflected sunlight2 
and  they were also conspicuous in the  
spectra of the planets4 ,it was thus    
proved that these lines were            
characteristic of sunlight1 whether     
direct  or reflected4 ,it was1 however1 
still possible that they might be caused
  by the passage of the rays of light   
from the celestial bodies through  the  
,earth's atmosphere4 ,in order to test  

this theory1 ,fraunhofer  examined the  
spectra of the brighter stars4 ,he found
 that the lines  visible in the solar   
spectrum were not to be seen in the     
spectra of the  stars1 thus proving that
 the lines were not merely an           
atmospheric  effect4 ,each star1        
,fraunhofer observed1 had a different   
spectrum from  both the ,sun and from   
other stars4 ,these spectra were also   
characterised  by numerous dark lines1  
much fainter than those in the solar    
spectrum4    ,although he ascertained   
the existence of the dark lines in the  
,sun's  spectrum1 ,fraunhofer never     
really found out what they represented4 
,as  ,miss ,giberne expresses it1       
8,although he now saw the lines he could
 not  understand them3 he could not read
 what they said4 ,they spoke to him     
indeed about the ,sun1 but they spoke to
 him in a foreign language1 the  key to 
which he did not possess40 ,however1 he 
expressed the belief that  the pair of  
lines in the solar spectrum1 which he   

marked ,d1 coincided  with the pair of  
bright lines emitted by incandescent    
sodium4 ,although  he doubtless         
suspected that the lines conveyed       
intelligence regarding  the elements in 
the ,sun1 he never was able properly to 
decipher their  meaning4 ,had he lived1 
he would probably have made the great   
discovery2  but these investigations    
were cut short by his sudden and        
untimely death  on ,june #g1 #ahbf4     
,after the death of ,fraunhofer1 very   
little was done to forward the study  of
 spectrum analysis4 ,investigations in  
this branch of research were  made1     
however1 by ,sir ,john ,herschel        
7#agib-ahga71 ,william ,allen  ,miller  
7#ahag-ahgj71 ,sir ,david ,brewster     
7#agha-ahfh71 and others4 ,two  famous  
men of science had partly discovered the
 secret4 ,these were ,sir  ,george      
,stokes 7#ahai-aijc71 of ,cambridge1 and
 ,anders ,john ,angstrm  7#ahab-ahgb7 of
 ,upsala4 ,of ,angstrm's work1 published
 in #ahec1 it has  been said that it    

would 8have obtained a high celebrity if
 it had  appeared in ,french1 ,english1 
or ,german1 instead of ,swedish40    ,it
 was not until #ahei that the principles
 of spectrum analysis were  fully       
enunciated by ,gustav ,robert ,kirchhoff
 7#ahbd-ahhg71 and his  colleague in the
 ,university of ,heidelberg1 ,robert    
,wilhelm ,bunsen  7#ahaa-ahii74         
,kirchhoff demonstrated that a luminous 
solid or liquid  gives a continuous     
spectrum1 and a gaseous substance a     
spectrum of  bright lines4 ,in the words
 of ,miss ,clerke1 8,substances of every
 kind are  opaque to the precise rays   
which they emit at the same temperature4
 ,that  is to say1 they stop the kinds  
of light or heat which they are then    
actually in a condition to radiate4444  
,this principle is fundamental to  solar
 chemistry4 ,it gives the key to the    
hieroglyphics of the ,fraunhofer  lines4
 ,the identical characters which are    
written bright in terrestrial  spectra  
are written dark in the unrolled sheaf  

of sun-rays40 ,kirchhoff  made several  
determinations of the substances in the 
,sun1 proving the  existence of sodium1 
iron1 calcium1 magnesium1 nickel1       
barium1 copper1  and zinc4 ,his great   
map of the solar spectrum was published 
by the  ,berlin ,academy in #ahfj1 and  
represented an enormous amount of       
labour4 ,it  was succeeded by another   
map by ,angstrm1 published in #ahfh4    
,but both of  these maps have been      
recently superseded by the              
investigations of ,sir  ,joseph ,norman 
,lockyer 7born #ahcf71 and of the       
,american physicist1  ,henry ,augustus  
,rowland 7#ahdh-aija74 ,rowland largely 
increased our  knowledge of the elements
 in the solar atmosphere4    ,the       
spectroscope had become1 by #ahfh1 a    
recognised instrument of  astronomical  
research1 and in that year it was       
applied during the famous  total        
eclipse1 visible in ,india4 ,there were 
many eclipse problems1  arising from the
 observations made by the eclipse       

expeditions of #ahdb1  #ahea1 and #ahfj4
 ,the eclipse of #ahea had finally      
proved that the red  flames seen        
surrounding the ,sun during total       
eclipses belonged to the  ,sun1 and not 
to the ,moon1 as many astronomers had   
believed4 ,at the  eclipse of #ahfj1    
visible in ,spain1 the ,italian         
astronomer1 ,angelo  ,secchi            
7#ahah-ahgh71 and the ,englishman1      
,warren ,de la ,rue 7#ahae-ahhi71       
secured photographs of the solar        
prominences4 ,the problem of #ahfh was  
the constitution of these prominences4  
,pierre ,jules ,csar ,janssen1 born in  
,paris in #ahbd1 was stationed at       
,guntoor1 in ,india1 to observe the     
eclipse4 ,he succeeded in observing the 
spectrum of the prominences during the  
progress of totality1 and found  it to  
be one of bright lines1 proving the     
gaseous nature of the  sun-flames4      
,during the progress of the eclipse1    
,janssen was specially  struck by the   
brilliancy of the bright lines1 and it  

occurred to him  that the               
prominence-spectrum could be observed in
 full daylight1 if  sufficient          
dispersive power was used to enfeeble   
the ordinary continuous  spectrum4 ,at  
ten o'clock on the following morning1   
,august #ai1 #ahfh1  ,janssen applied   
his spectroscope to the sun1 and        
observed the  prominence-spectrum4      
,after a month's observation in ,india1 
he sent to  the ,french ,academy an     
account of his success4 ,a short time1  
however1  before his report arrived1 the
 ,academy had received a similar one    
from  ,lockyer1 who had independently   
made the same discovery4 ,two years     
previously1 in #ahff1 the new method had
 occurred to him1 but his  spectroscope 
was not powerful enough2 and although he
 ordered a more  powerful one at once1  
it was not until ,october #af1 #ahfh1   
that he had the  instrument in his      
hands4 ,four days later he observed the 
prominence-spectrum in full daylight4   
,the next advance in the study of the   

prominences was announced in #ahfi4     
,janssen and ,lockyer had shown         
astronomers how to observe the spectrum 
of  the prominences2 but the researches 
of other two famous astronomers  enabled
 observers to see the forms of the      
prominences4 ,these two men  were       
,william ,huggins 7born #ahbd7 and      
,johann ,carl ,friedrich ,zllner4  ,the 
latter astronomer1 born in ,leipzig in  
#ahcd1 was one of the most  successful  
students of the solar prominences4 ,he  
was ,professor of  ,astrophysics in the 
,university of ,leipzig1 a position     
which he filled  with success until his 
untimely death on ,april #be1 #ahhb4    
,independently  of ,huggins1 he found   
that by opening the slit of the         
spectroscope wider1  the forms of the   
prominences themselves could be seen4   
,the study of the  prominences was at   
once taken up by the most famous solar  
observers3  these were ,huggins and     
,lockyer in ,england1 ,sprer and ,zllner
 in  ,germany1 ,janssen in ,france1     

,secchi1 ,respighi1 and ,tacchini in    
,italy1  ,young in ,america4 ,to        
,charles ,augustus ,young 7born #ahcd7  
we owe the  careful study of individual 
prominences4 ,on ,september #g1 #ahga1  
he  observed the most gigantic outburst 
on the sun ever witnessed1 fragments  of
 an exploded prominence reaching a      
height of #ajj1jjj miles3 ,young1  also1
 made the first attempt to photograph   
the prominences4    ,to the ,italian    
school of astronomers1 however1 we owe  
the persistent and  systematic study of 
the prominences4 ,among them the three  
greatest names  are ,angelo ,secchi     
7#ahah-ahgh71 ,lorenzo ,respighi        
7#ahbd-ahhi71 and  ,pietro ,tacchini    
7#ahch-aije74 ,after the death of       
,secchi1 the recognised  head of        
spectroscopy in ,italy was ,pietro      
,tacchini4 ,born at ,modena in  #ahch1  
he was appointed director at ,modena in 
#ahei1 assistant at ,palermo  in #ahfc1 
and director at ,rome in #ahgi4 ,in     
#ahgj he commenced to take  daily       

observations of the prominences1 noting 
their sizes1 forms1 and  distribution1  
and these observations were continued   
for thirty-one  years1 until within four
 years of ,tacchini's death1 which took 
place on  ,march #bd1 #aije4 ,tacchini  
did for the study of the prominences    
what  ,schwabe did for the spots4 ,the  
,italian spectroscopists found that the 
prominences increased and decreased     
every eleven years in harmony with  the 
spots4 ,tacchini demonstrated that the  
streamers of the solar corona  originate
 in regions where the prominences are   
most numerous1 and that  the shape of   
the corona1 on the whole1 varies in     
sympathy with the  prominences4    ,the 
researches of ,lockyer indicated that   
the prominences originated in a  shallow
 gaseous atmosphere which he termed the 
chromosphere4 ,formerly  astronomers had
 to observe only isolated prominences1  
but in #ahib an  ,american astronomer1  
,george ,ellery ,hale 7born #ahfh71     
formerly director  of the ,yerkes       

,observatory1 and now director of the   
,solar ,observatory in  ,california1    
succeeded in photographing1 by an       
ingenious process1 the  whole of the    
chromosphere1 prominences1 and facul    
visible on the solar  surface4          
,another solar envelope was discovered  
in #ahgj by ,dr ,charles ,augustus      
,young1 who from #ahff to #ahgg directed
 the ,observatory at ,dartmouth1 ,new   
,hampshire1 and from #ahgg to #aije1    
that at ,princeton1 ,new ,jersey4       
,during  the eclipse of ,december #bb1  
#ahgj1 ,young was stationed at ,tenez de
  ,frontena1 ,spain4 ,as the solar      
crescent grew apparently thinner before 
the disc of the ,moon1 8the dark lines  
of the spectrum10 he says1 8and  the    
spectrum itself gradually faded away1   
until all at once1 as suddenly  as a    
bursting rocket shoots out its stars1   
the whole field of view was  filled with
 bright lines1 more numerous than one   
could count4 ,the  phenomenon was so    
sudden1 so unexpected1 and so           

wonderfully beautiful1  as to force an  
involuntary exclamation40 ,the          
phenomenon was observed for  two        
seconds1 and the impression was left on 
the astronomer that a bright  line had  
taken the place of every dark one in the
 solar spectrum1 the  spectrum being    
completely reversed4 ,hence the name    
which was given to  the hypothetical    
envelope--8the reversing layer40 ,for   
long the existence  of the reversing    
layer was disputed by numerous          
astronomers4 ,in #ahif  photographs     
taken during the solar eclipse of that  
year finally  demonstrated the existence
 of the 8flash spectrum0 as seen by     
,young4    ,the last of the solar       
appendages1 the corona1 can only be seen
 during  total eclipses4 ,the researches
 of ,young and ,janssen indicate that it
 is  partly gaseous and partly meteoric 
in its constitution2 and various        
photographs1 taken at the eclipses since
 #ahgj1 have demonstrated its  variation
 in shape1 which is in harmony with the 

eleven-year period4  ,several attempts  
have been made to observe the corona    
without an  eclipse4 ,in #ahhb ,huggins 
made the attempt1 but failed1 and ,hale1
 with  his photographic process1 had no 
better success4 ,more recently1 in      
#aijd1  a ,russian astronomer1 ,alexis  
,hansky1 observing from the top of ,mont
  ,blanc1 secured some photographs on   
which he believes the corona is         
represented1 but so far his observations
 have not been confirmed by  other      
astronomers4    ,the application of the 
spectroscope to the motions on the solar
 surface  is perhaps one of the most    
wonderful triumphs in astronomical      
science4  ,in #ahdb ,christian ,doppler 
7#ahjc-ahec71 ,professor of ,mathematics
 at  ,prague1 had expressed the view    
that the colour of a luminous body must 
be changed by its motion of approach or 
recession4 ,it was obvious to  ,doppler 
that if the body was approaching1 a     
larger number of light waves  must be   
entering the eye of the observer than if

 it were retreating4  ,miss ,clerke thus
 illustrates ,doppler's principle3      
8,suppose shots to be  fired at a target
 at fixed intervals of time4 ,if the    
marksman advances1  say1 twenty paces   
between each discharge of his rifle1 it 
is evident  that the shots will fall    
faster on the target than if he stood   
still2  if1 on the contrary1 he retires 
by the same amount1 they will strike at 
correspondingly longer intervals40 ,it  
occurred to various astronomers  that it
 would be possible to measure cyclones  
and hurricanes in the ,sun1  not by     
change of colour in the spectrum1 but by
 the shifting of the  lines2 and in     
#ahgj this was successfully done by     
,lockyer4 ,in the next  few years       
efforts to measure the solar rotation   
were made by ,young1  ,zllner1 and      
others1 who succeeded in measuring the  
displacement of the  lines1 but not the 
time of rotation4 ,this was reserved for
 the famous  ,swedish astronomer1 ,dunr4
    ,nils ,christopher ,dunr1 born in   

#ahci in ,scania1 was employed as an    
assistant at ,lund ,observatory from    
#aheh to #ahhh1 when he was appointed   
director of the ,observatory at ,upsala4
 ,in that year he commenced a study  of 
the solar rotation1 measuring it by     
means of ,doppler's principle4 ,he      
confirmed the telescopic work of        
,carrington and ,sprer on the equatorial
  acceleration1 and measured the        
displacement up to within fifteen       
degrees  of the poles4 ,he brought out  
the surprising fact that the rotation   
period of the ,sun is there protracted  
to #ch days4 ,these remarkable          
researches were published in #ahia4     
,in #ahgc the ,astronomer-,royal of     
,england commenced at ,greenwich        
,observatory to photograph the ,sun     
daily4 ,this work has been carried on   
there by ,edward ,walter ,maunder 7born 
#ahea71 and ,greenwich ,observatory     
possesses a photographic record of      
sun-spots4 ,at the ,meudon              
,astrophysical ,observatory1 near       

,paris1 ,janssen has1 since #ahgf1      
secured  photographs of the solar       
surface1 which were comprised in a great
 atlas1  published by him in ,january   
#aijd4 ,these photographs have revealed 
a  remarkable phenomenon--the 8rseau    
photospherique10 the distribution over  
the solar surface of blurred patches of 
light1 which ,janssen considers  are    
inherent in the ,sun4 ,the ,greenwich   
records of sun-spots and of  magnetic   
disturbances have been made use of by   
,maunder in his remarkable  studies1    
promulgated in #aijd1 of the connection 
between sun-spots and  terrestrial      
magnetism4 ,maunder finds that on the   
average magnetic storms  are dependent  
on the presence of sun-spots1 and on the
 size of the spot4  ,the magnetic       
action1 he finds1 does not radiate      
equally in all  directions from the     
sun-spots1 but along definite and       
restricted lines4    ,herschel's        
hypothesis of a dark and cool globe     
beneath the solar  photosphere was seen 

to be untenable after the introduction  
of the  spectroscope4 ,the first        
important theory as to the solar        
constitution  was that advanced in #ahfe
 by the ,french astronomer1 ,herv ,faye 
7#ahad-aijb74 ,numerous other theories  
were afterwards advanced by ,secchi1    
,zllner1 ,young1 and others1 but a      
complete description of the various     
developments in solar theorising cannot 
be given here4 ,there is no  complete   
8theory0 of the exact constitution of   
every part of the ,sun1  but the        
unpretentious 8,views of ,professor     
,young on the ,constitution of  the     
,sun10 which appeared in ,april #aijd in
 #8,popular ,astronomy1' represent  the 
latest ideas of the foremost solar      
investigator4 ,professor ,young  regards
 the reversing layer and the            
chromosphere as 8simply the  uncondensed
 vapours and gases which form the       
atmosphere in which the  clouds of the  
photosphere are suspended40 ,he says    
that the contraction  theory of         

,helmholtz1--explained in another       
chapter1--advanced to explain  the      
maintenance of the ,sun's heat1 is true 
so far as it goes2 but that  it is all  
the truth is now made doubtful by the   
discovery of radium1  which 8suggests   
that other powerful sources of energy   
may co-operate  with the mechanical in  
maintaining the ,sun's heat40    ,the   
important question of the distance of   
the ,sun was thoroughly  investigated in
 #ahbd by ,johann ,franz ,encke         
7#agia-ahfe71 then of  ,seeberg1 near   
,gotha1 who1 from a discussion of the   
transits of ,venus in  #agfa and #agfi1 
found a parallax of #hega1 corresponding
 to a mean  distance of #ie1jjj1jjj     
miles4 ,this value was accepted for     
thirty years1  until ,peter ,andreas    
,hansen 7#agie-ahgd71 in #ahed1 and     
,urban ,jean  ,joseph ,le ,verrier      
7#ahaa-ahgg71 in #aheh1 found from      
mathematical  investigations that the   
distance indicated was too great4       
,preparations  were accordingly made for

 the observation of the transits of     
,venus1  which took place respectively  
on ,december #h1 #ahgd1 and ,december   
#f1 #ahhb4  ,on the first occasion many 
expeditions were sent to view the       
transit1  consisting of ,french1        
,german1 ,american1 ,english1 ,scottish1
 ,italian1  ,russian1 and ,dutch        
astronomers1 and it was hoped that the  
solar parallax  would be accurately     
measured once for all4 ,however1 the    
transit1  although favoured with good   
weather1 was not successful1 owing to   
the  difficulty of making exact         
measurements1 by reason of the          
illumination  and refraction in the     
atmosphere of ,venus4 ,accordingly the  
values  deduced for the parallax were   
far from unanimous4 ,the transit of     
#ahhb  was not observed so extensively1 
as astronomers had found the transit of 
,venus to be by no means the best       
method4 ,in #ahgg ,sir ,david ,gill     
7born  #ahdc71 the great ,scottish      
astronomer1 determined the solar        

parallax  successfully from measures of 
the parallax of ,mars in opposition4    
,his  value was #hgh1 corresponding to  
#ic1jhj1jjj miles4 ,some years previous 
to this ,johann ,gottfried ,galle 7born 
#ahab71 the ,german astronomer1  had1   
from measurements of the parallax of the
 asteroid ,flora1 deduced a  solar      
parallax of #hhg4 ,gill's work at the   
,cape in #ahhh1 on the  ,asteroids1 was 
successful in giving a more accurate    
value than the  transit of ,venus3 in   
#aijj and #aija measures of the parallax
 of the  asteroid ,eros1 the nearest    
minor planet1 were made by many         
different  observatories1 and agree with
 the other results4 ,the values which   
have  been derived from the velocity of 
light1 and from the constant of         
aberration1 are fairly in agreement with
 those derived from direct  measurement4
 ,on the whole1 the most probable value 
of the parallax is  about #hh1          
indicating a mean distance of about     
#ib1gjj1jjj miles1 with a  8probable    

error0 of about #aej1jjj miles4    ,what
 a different picture the sun presents to
 us at the beginning of the  twentieth  
century from that which it presented to 
,herschel and his  contemporaries at the
 beginning of the nineteenth6 ,to       
,herschel1 the ,sun  was a cool dark    
globe1 surrounded by a luminous         
atmosphere4 ,as the  outcome of the     
researches and discoveries outlined in  
this chapter1 the  ,sun is now seen to  
be a vast central world1 which is over a
 million  times larger than the ,earth4 
,in the words of an able writer1 8,it is
 most  probably a world of gases1 where 
most of the metals and metallic gases   
that we know exist only as vapours1 even
 at the ,sun's surface1 hotter  than any
 furnace on earth1 and getting a still  
fiercer heat for every  mile of descent 
lower4 ,of that heat in the ,sun's      
interior we can form no  conception4    
,the pressure within the ,sun is equally
 inconceivable4 ,a  cannon-ball weighing
 #ajj lb4 on earth would weigh #bgjj on 

the ,sun4 ,thus  a mighty conflict goes 
on unceasingly between imprisoned and   
expanding  gases and vapours struggling 
to burst out1 and massive pressures     
holding  them down4 ,for reasons we     
cannot fully understand1 no equilibrium 
is  reached4 ,for millions of years     
up-rushes and down-rushes of the        
white-hot materials have been proceeding
 on that bright photosphere  which gives
 us light1 and looks a picture of calm  
and quiescence4 ,above  that is a       
comparatively thin rose-coloured layer1 
the chromosphere1  agitated with fiery  
#8prominences1' and outside all these   
the coronal  glory--all alike pointing  
to immeasurable activities40    ,the    
following remark of ,professor ,newcomb 
shows our inability to realise  the     
solar activity4 8,suppose10 he says1    
8every foot of space in a whole  country
 covered with #ac-;inch cannon1 all     
pointed upward1 and all  discharged at  
once4 ,the result would compare with    
what is going on  inside the photosphere

 about as much as a boy's popgun        
compares with the  cannon40             
,,chapter ,,iv4                         
,,the ,,moon4      ,it is somewhat      
remarkable that the one celestial body  
which ,herschel  neglected was our      
satellite1 the ,moon2 and it is also    
remarkable that  the ,moon was for many 
years the chief object of study of his  
contemporary astronomer1 ,johann        
,hieronymus ,schrter 7#agde-ahaf74 ,born
  at ,erfurt1 near ,hanover1 on ,august 
#cj1 #agde1 ,johann ,hieronymus ,schrter
  was originally intended for the study 
of law1 for which he was sent to  the   
,university of ,gttingen4 ,at the same  
time he studied mathematics1  and       
particularly astronomy1 under the       
mathematician1 ,kaestner of  ,gttingen4 
,deeply interested in music1 he became  
acquainted with the  ,herschel family1  
and1 inspired by ,william ,herschel's   
example1 determined  to study the       
heavens4 ,in #aggi he became the        
possessor of a small  achromatic        

refractor1 and commenced to observe the 
,sun and ,moon4 ,in #aggh  he entered   
the legal profession at ,hanover1 and   
four years later he was  appointed      
8oberamtmann0 or ,chief ,magistrate of  
,lilienthal--8the ,vale of  ,lilies0--in
 the ,duchy of ,bremen4 ,at ,lilienthal 
,schrter erected a small  observatory1  
and acquired in #aghe one of ,herschel's
 #g-;foot reflectors4  ,in #agib the    
astronomer superintended the            
construction of a #ac-;foot  reflector1 
made by ,schrader of ,kiel1 who         
transferred his workshop to             
,lilienthal4 ,with these instruments the
 great work of ,schrter was             
accomplished4    ,schrter directed his  
powers of observation to the study of   
the ,moon4 ,he  originated the study of 
the surface of the ,moon1 and founded   
the branch  of astronomy known as       
selenography1 or the study of the       
,moon's surface4  ,the foundations of   
this branch were laid in #agia with the 
publication of  ,schrter's              

#8,seleno-topographische ,fragmente'4   
,the astronomer determined  to make a   
comparative study of the surface of our 
satellite1 and before  #ahja discovered 
eleven 8rills0 or clefts on the ,moon's 
surface1 and  recognised a large number 
of craters4 ,he likewise believed that  
he had  seen a lunar atmosphere1 an     
observation of which was made by him in 
,february #agib4 ,schrter seems never to
 have doubted what ,herschel and  his   
contemporaries believed--that the ,moon 
was a living world with  volcanoes in   
active eruption1 surrounded by an       
atmosphere1 and inhabited  by beings    
like ourselves4 ,unfortunately1 ,schrter
 was not good at making  drawings of    
what he saw2 nevertheless1 he           
accomplished a vast amount of  work4 ,in
 the little observatory at ,lilienthal  
the foundations were laid  of the       
comparative study of the surface of the 
,moon4    ,but these observations were  
destined to be rudely interrupted4 ,in  
#ahaj  ,hanover was occupied by the     

invading troops of ,napoleon1 and       
,schrter  lost his appointment as ,chief
 ,magistrate of ,lilienthal1 and also   
his  income4 ,but there was worse to    
follow4 ,on ,april #bj1 #ahac1 three    
years  after1 the ,french1 under        
,vandamme1 with that cruelty which seems
 to  belong to warfare1 occupied        
,lilienthal1 and set fire to the little 
village4 ,a few days later the ,french  
soldiers entered the observatory  and   
burned it to the ground4 ,all ,schrter's
 precious observations1  accumulated    
after thirty-four years' labour1 were   
destroyed with a few  exceptions1 the   
observations on ,mars narrowly escaping 
the  conflagration4 ,unable to forget   
the destruction of his observatory1 and 
without the means to repair the loss1 he
 lived only three years after  the      
disaster4 ,he died on ,august #bi1      
#ahaf1 8leaving behind him10 says ,mr   
,arthur ,mee1 8an imperishable record1  
and a noble example to observers of  all
 time40    ,wilhelm ,gotthelf ,lohrmann1

 a land-surveyor of ,dresden1 continued 
the  observations of ,schrter1 and in   
#ahbd published four of the twenty-five 
proposed sections of a large lunar      
chart4 ,in #ahbg1 however1 his sight    
began to fail1 and he was obliged to    
abandon his intention4 ,but a  successor
 had already appeared on the scene4     
,johann ,heinrich von  ,mdler           
7#agid-ahgd7 was born in ,berlin in     
#agid1 and1 after a severe  struggle to 
earn a living1 entered the ,university  
of ,berlin in #ahag4 ,in  #ahbd he      
became acquainted with ,wilhelm ,beer   
7#agig-ahej71 a wealthy  banker1 who had
 come to him for instruction in         
astronomy1 and who  erected in #ahbi an 
observatory near his villa in ,berlin1  
where pupil and  tutor pursued their    
studies4    ,in #ahcj ,mdler1 with      
,beer's assistance1 commenced a great   
trigonometrical survey of the surface of
 the ,moon4 ,the observations of  ,beer 
and ,mdler were made with no larger     
instrument than a #c-;inch  refractor4  

,they ascertained the positions of #iai 
lunar spots1 and  measured the height of
 #ajie mountains4 ,their great chart of 
the  ,moon--which was afterwards        
followed by a smaller one--was issued in
 four  parts during #ahcd-cf4 8,the     
amount of detail10 wrote ,proctor1 8is  
remarkable1 and the labour actually     
bestowed upon the work will appear      
incredible40 ,the chart has neither been
 revised nor superseded1 and it  remains
 to this day one of the standard works  
on the subject4    ,the chart was       
succeeded in #ahcg by a descriptive     
volume entitled #8,der  ,mond4' ,in this
 work ,beer and ,mdler did much for the 
progress of lunar  astronomy4 ,their    
observations led to a change of opinion 
regarding our  satellite's physical     
condition4 ,herschel1 ,schrter1 ,olbers1
 and other  astronomers seem to have    
considered the ,moon a living world4    
,mdler  declared that it was a dead     
world4 ,he believed it to be destitute  
of  life of any kind1 and the changes   

observed by ,schrter and other          
observers were put down as illusions4   
#8,der ,mond' was the end of ,mdler's   
work in lunar astronomy1 for1 receiving 
an appointment at ,dorpat1 he  went     
there in #ahdf1 and retained his post   
until within a few years of  his death1 
which took place at ,hanover on ,march  
#ad1 #ahgd4    ,mdler's successor in the
 field of lunar astronomy was ,johann   
,friedrich  ,julius ,schmidt            
7#ahbe-ahhd71 who was born at ,eutin in 
,lbeck in #ahbe4 ,at  a very early age  
he gave indications of a taste for      
astronomy4  ,fortunately his father     
possessed a small hand telescope1 with  
which  young ,schmidt commenced his     
lunar studies4 ,appointed assistant at  
,bonn  and ,olmtz and director at       
,athens successively1 he kept up his    
persistent study of the surface of the  
,moon for over forty years4 ,in  #ahci1 
when fourteen years of age1 he began the
 valuable series of  observations which 
were destined to form the basis of his  

great chart of  the surface of the      
,moon4 ,between #ahec and #aheh1 when   
employed at ,olmtz1  ,schmidt made and  
calculated no fewer than #djjj          
micrometrical measures of  the altitudes
 of lunar mountains4 ,before #ahff      
,schmidt had found no fewer  than #bgh  
8rills10 and his discoveries were the   
means of augmenting the  number of these
 curious objects to nearly a thousand4  
,in a word1 it may be said that ,schmidt
 drew out a lunar geography1 and  the   
result of his labours1 together with    
those of ,schrter and ,mdler1  is that  
in a sense we now know the features of  
the ,moon better than  those of the     
,earth4 ,for instance1 astronomers see  
the whole surface of  the ,moon spread  
before their eyes1 while geographers can
 never have a  similar view of the      
terrestrial features3 we have never seen
 the poles  of the ,earth1 while the    
lunar poles are well known to           
astronomers4 ,for  twenty years after   
his appointment at ,athens1 ,schmidt    

worked at fixing  the positions of lunar
 objects1 measuring the heights of      
mountains and  the depths of craters4   
,an idea of his enthusiasm in           
constructing his  great chart may be    
gained from the fact that he made almost
 a thousand  original sketches4         
,mdler's dogmatic assertion that the    
,moon was entirely a dead world was     
generally believed until ,schmidt made  
observations to the contrary4 ,from     
#ahcg to #ahff the popular opinion was  
that our satellite was an  absolutely   
dead world4 ,consequently there was     
little progress in lunar  astronomy     
during those thirty years4 ,although    
,mdler's view was much  nearer the truth
 than the opinions of his predecessors1 
it was also too  positive4 ,his         
confident assertion1 which was received 
without  hesitation1 was never          
questioned until ,schmidt came upon the 
scene4 ,to  ,schmidt the ,moon was not  
entirely dead1 and it was he who brought
  forward indisputable evidence as to   

the existence of changes on its         
surface4 ,in ,october #ahff he announced
 that the crater ,linn had lost all     
appearance of such1 and that it had     
become entirely effaced4 ,lohrmann  and 
,mdler had observed it under a totally  
different aspect1 as also had  ,schmidt 
himself from #ahdj to #ahdc4 ,there was 
great excitement in the  astronomical   
world on ,schmidt's announcement1 and   
many astronomers  denied the change1    
although ,schmidt's observation was     
confirmed by  ,secchi and ,webb4 ,the   
evidence in favour of it preponderated1 
and very  few observers now consider the
 ,moon's surface to be absolutely       
changeless4    ,in #ahfe ,schmidt had   
begun to arrange his observations on the
 ,moon into  the form of a chart4 ,at   
first he decided to have a chart of six 
feet  diameter1 divided1 like that of   
,mdler1 into four sections4 ,but in     
,april  #ahfh1 on making an estimate of 
the value of such a chart1 he was       
dissatisfied1 and determined to         

construct a map of the same size divided
  into twenty-five sections instead of  
four4 ,he began the work in #ahfh1  and 
after six years the great map was       
completed4 ,after some delay the        
,german ,government undertook to issue  
the chart at their expense1 and it  was 
published in #ahgi1 after fourteen years
 of preparation4 ,it contained  no fewer
 than #cj1jjj objects1 and its completed
 diameter was six feet  three           
inches--more than double the size of any
 previous map of the ,moon4  ,indeed1 it
 was probably the greatest contribution 
ever made to lunar  astronomy4 ,schmidt 
lived only a few years after the        
publication of his  great chart4 ,he    
died at ,athens1 in his fifty-ninth     
year1 ,february #h1  #ahhd4             
,schmidt's announcement of the change in
 the appearance of ,linn was  followed  
in #ahgh by a statement by ,hermann     
,joseph ,klein 7born #ahdb7 of          
,cologne1 to the effect that a new      
crater had been formed to the north of  

the well-known lunar crater1 ,hyginus4  
,the change in this case1 however1  is  
by no means so certain as in that of    
,linn4 ,it will be observed that  the   
majority of the students of the ,moon   
were ,germans4 ,in ,england the  study  
was not taken up until #ahfd1 when a    
,lunar ,committee of the ,british       
,association was appointed4 ,some good  
lunar work was done by the  well-known  
astronomer1 ,thomas ,william ,webb      
7#ahjg-ahhe71 while the  study was      
popularised by ,james ,nasmyth          
7#ahjh-ahij71 the famous  engineer1 who 
published1 in #ahgd1 in conjunction with
 ,james ,carpenter  of ,greenwich       
,observatory1 a beautifully-illustrated 
volume entitled #8,the  ,moon4' ,this   
was succeeded1 in #ahgf1 by the larger  
work of ,edmund  ,neison 7now ,nevill71 
,government ,astronomer of ,natal4      
,about this time  several ,english      
astronomers1 devoted to the study of the
 ,moon1 formed  themselves into the     
,selenographical ,society4 ,after a few 

years1 however1  the society came to an 
end1 and the enthusiasts formed         
themselves into  the lunar section of   
the ,british ,astronomical ,association1
 on the  foundation of that society in  
#ahij4 ,chief among those ,english      
selenographers was ,thomas ,gwyn ,elger 
7#ahcg-ahig71 whose observations  of the
 ,moon and drawings of the various      
craters were of the utmost  value4 ,two 
years before his death1 in #ahie1 ,elger
 published his  important work1 #8,the  
,moon1' along with an exhaustive chart  
of the  visible face of our satellite4  
,herschel and ,schrter firmly believed  
in the existence of a lunar  atmosphere1
 the latter believing that he had       
actually observed the  ,moon's          
atmospheric envelope4 ,early in the     
nineteenth century it was soon          
observed1 however1 that on the ,moon    
passing over and occulting stars1  these
 stars disappeared suddenly behind the  
,moon's limb1 instead of  gradually1 as 
they should have done1 had an atmosphere

 of any density  existed4 ,accordingly  
astronomers gave up believing in a lunar
  atmosphere4 ,on ,january #d1 #ahfe1   
,huggins observed with his spectroscope 
the occultation of a small star in      
,pisces4 ,there was not the slightest   
sign of absorption in a lunar           
atmosphere2 the entire spectrum vanished
  at once4    ,lunar photography was    
introduced as long ago as #aheh by      
,lewis ,morris  ,rutherfurd             
7#ahaf-ahib71 the well-known ,american  
astronomer2 but for  years very little  
was done in this matter1 although       
,rutherfurd secured  fairly good        
photographs4 ,rutherfurd1 ,de la ,rue1  
and the older  astronomical             
photographers took photographs of the   
entire ,moon1 but this  plan was        
abandoned in favour of what ,miss       
,clerke calls 8bit by bit  photography40
 ,about #ahij this method was           
introduced1 and has been  followed with 
success by ,maurice ,loewy 7born #ahcc71
 and his assistant1  ,pusiex1 at the    

,paris ,observatory2 by ,ladislas       
,weinek at ,prague2 by the  astronomers 
of the ,lick ,observatory2 and by       
,william ,henry ,pickering  7born       
#aheh71 the distinguished astronomer of 
,harvard1 whose discoveries  and        
investigations have created quite a new 
interest in lunar astronomy4  ,these    
investigations were commenced in #ahia  
at ,arequipa1 on the slope of  the      
,andes1 in ,peru4 ,an occultation of    
,jupiter1 witnessed by ,w4 ,h4          
,pickering on ,october #ab1 #ahib1 gave 
support to the view that a very  tenuous
 lunar atmosphere does exist4 ,in #aijj 
he established1 near  ,mandeville1      
,jamaica1 a temporary astronomical      
station1 where he obtained  many        
excellent photographs4 ,totally he      
secured eighty plates4 ,these  appeared1
 as the first complete photographic     
lunar atlas ever published1  in his work
 #8,the ,moon' 7#aijc71 in which he sums
 up all his observations  since #ahia1  
and concludes that 8the evidence in     

favour of the idea that  volcanic       
activity upon the ,moon has not yet     
ceased is pretty strong1 if  not fairly 
conclusive40    ,pickering points out   
that the density of the lunar atmosphere
 is not  greater than one ten-thousandth
 of that at the ,earth's surface1 and1  
under these circumstances1 water cannot 
exist above freezing-point1  which of   
course brings us to the subject of snow4
 ,he considers that snow  is observed on
 the mountain peaks and near the poles  
of the ,moon1 and he  believes his      
conclusion to be verified by            
observations on the well-known  crater1 
,linn4 ,he brings forward evidence of   
the probable existence on  the ,moon of 
organic life1 pointing out that the     
difference between the  conditions of   
the ,earth and the ,moon is not so great
 as that above and  below the ocean on  
our own planet4 ,he has collected       
evidence of the  existence of something 
resembling vegetation on the ,moon      
8coming up1  flourishing1 and dying1    

just as vegetation springs and withers  
on the  ,earth40    ,the first          
successful attempt to measure the       
heating power of moonlight  was made in 
#ahdf on ,mount ,vesuvius by ,melloni1  
an ,italian physicist1  whose results   
were confirmed four years later by      
,zantedeschi1 another  ,italian4 ,the   
most important work in this direction   
was accomplished by  the present ,earl  
of ,rosse 7born in #ahdj71 who in the   
years #ahfi-gb  believed himself to have
 measured the lunar heat2 but these     
conclusions  were not altogether        
confirmed by the observations of ,dr    
,otto  ,boeddicker 7,lord ,rosse's      
astronomer71 during the total lunar     
eclipse of  ,october #d1 #ahhd4 ,further
 investigations on this subject were    
afterwards  made by ,samuel ,pierpont   
,langley 7#ahcd-aijf71 of ,alleghany1   
and by his  assistant1 ,frank ,very4    
,the motion of the ,moon and its        
perturbations were made the subject of  
deep study by the famous ,pierre ,simon 

,laplace 7#agdi-ahbg71 the  contemporary
 of ,herschel1 and the worthy successor 
of ,newton4 ,he devoted  much attention 
to the secular acceleration of the      
,moon's mean motion1 a  problem which   
had baffled the greatest mathematicians4
 ,after a profound  discussion he found1
 in #aghg1 that the average distance of 
the ,earth and  ,moon from the ,sun had 
been slowly increasing for several      
centuries1 the  result being an increase
 in the ,moon's velocity4 ,in the third 
volume of  the #8,mcanique ,cleste'     
,laplace worked out the lunar theory in 
great  detail1 although he calculated no
 lunar tables4 ,after his death the     
subject was taken up by ,charles        
,theodore ,damoiseau 7#agfh-ahdf71 and  
the most important advance was made by  
,giovanni ,antonio ,amadeo ,plana       
7#agha-ahfd71 the director of the ,turin
 ,observatory1 who published in  #ahcb a
 very complete lunar theory4 ,the work  
of ,plana was followed by  that of      
,peter ,andreas ,hansen 7#agie-ahgd71   

whose lunar tables were used  for the   
,nautical ,almanac1 and whom ,professor 
,simon ,newcomb considers to  be the    
greatest master of celestial mechanics  
since ,laplace4 ,the theory  of the     
,moon's motion was worked out in detail 
by the famous astronomer  ,charles      
,eugene ,delaunay 7#ahaf-ahgb71 who from
 #ahgj till #ahgb occupied  the post of 
director of the ,paris ,observatory4    
,delaunay was about to  work out the    
lunar tables when1 in #ahgb1 he was     
accidentally drowned by  the capsizing  
of a pleasure-boat at ,cherbourg4 ,the  
work accomplished in  this direction by 
,simon ,newcomb 7born #ahce7 is of great
 importance1  particularly in his       
correction of ,hansen's tables4 ,john   
,couch ,adams  7#ahai-ahib71 one of the 
discoverers of ,neptune1 while at work  
on the  lunar theory1 had occasion to   
correct ,laplace's supposed solution of 
the  acceleration of the lunar motion4  
,on going over the calculation ,adams   
found that several quantities1 omitted  

by ,laplace as unimportant1 showed  that
 the ,moon has a minute increase of     
speed for which the theory of           
gravitation will not account1--a        
conclusion opposed by ,plana1 ,hansen1  
and  ,pontcoulant1 but fully confirmed  
by ,delaunay4 ,delaunay suggested in    
#ahfe that the minute apparent increase 
was due to the retardation of the       
,earth's rotation by tidal friction4    
,this brings us to the subject of       
celestial evolution1 which is discussed 
in another chapter4                     
,,chapter ,v4                           
,,the ,,inner ,,planets4      ,much     
progress has been made during the last  
hundred years in our  knowledge of the  
planets4 ,in fact1 the study of ,mercury
 only dates from  the commencement of   
the nineteenth century4 ,our knowledge  
of the  vicinity of the ,sun is very    
limited1 and ,mercury is difficult of   
observation4 ,so limited1 in fact1 is   
our knowledge of the ,sun's             
surroundings1 that it is not yet known  

for certain whether there is a  planet1 
or planets1 between ,mercury and the    
,sun4 ,perturbations in the  motion of  
the perihelion of ,mercury's orbit led  
,le ,verrier in #ahei to  the belief    
that a planet of about the size of      
,mercury1 or else a zone of  asteroids1 
existed between ,mercury and the ,sun4  
,it was1 however1 obvious  that such a  
planet could only be seen when in       
transit across the ,sun's  disc1 or     
during a total eclipse4 ,meanwhile a    
,french doctor1 ,lescarbault1  informed 
,le ,verrier that he had seen a round   
object in transit over the  ,sun's disc4
 ,le ,verrier1 certain that this was the
 missing planet1 named  it 8,vulcan10   
and calculated its orbit1 assigning it a
 revolution period  of twenty days4 ,but
 it was never seen again4 ,transits of  
8,vulcan0 were  fixed for #ahgg and     
#ahhb1 but nothing was seen on these    
dates4 ,during the  total eclipse of    
,july #bi1 #ahgh1 two observers--,james 
,watson  7#ahch-ahhj71 the well-known   

astronomer1 and ,lewis ,swift 7born     
#ahbj7--;believed themselves to have    
discovered two separate planets1 and    
ultimately claimed two planets each1    
which were never heard of again4        
,during the total eclipse of #ahhc an   
active watch for 8suspicious  objects0  
was kept1 but with no result4 ,at the   
eclipses of #aijj and #aija             
respectively1 photographs were exposed  
by the ,american astronomers1 ,w4  ,h4  
,pickering and ,charles ,dillon ,perrine
 7born #ahfg71 but on none of  these    
plates could any trace of 8,vulcan0 be  
found4 ,at the total eclipse  of ,august
 #cj1 #aije1 plates were again exposed1 
but no announcement has  been made of an
 intra-,mercurial planet2 and the       
prevalent opinion among  astronomers is 
that no planet comparable with ,mercury 
in size exists  between that planet and 
the ,sun4    ,the study of the physical 
appearance of ,mercury was inaugurated  
by  ,schrter1 who in #ahjj noticed that 
the southern horn of the crescent       

presented a blunted appearance1 which he
 attributed to the existence of  a      
mountain eleven miles in height4 ,from  
observations of this mountain he  came  
to the conclusion that the planet       
rotated in #bd hours #d minutes4  ,this 
was afterwards reduced by ,friedrich    
,wilhelm ,bessel 7#aghd-ahdf7 to  #bd   
hours #ec seconds4    ,after the time of
 ,schrter there was no astronomer who   
paid much  attention to either ,mercury 
or ,venus until the arrival on the scene
 of  the most persistent planetary      
observer and one of the foremost        
astronomers of the nineteenth century4  
,giovanni ,virginio ,schiaparelli  was  
born at ,savigliano1 in ,piedmont1 in   
#ahce1 and graduated at ,turin in       
#ahed4 ,called to ,milan as assistant in
 the ,brera ,observatory in #ahfj1 he   
became director in #ahfb1 and there for 
thirty-eight years he studied  astronomy
 in all its aspects1 making a great name
 for himself in various  branches of the
 science4 ,in #aijj he retired from the 

post of director1  and pursues his      
astronomical researches in his          
retirement4    ,in #ahhb ,schiaparelli  
took up the study of ,mercury in the    
clear air of  ,milan4 ,instead of       
observing the planet through the evening
 haze1 like  ,schrter and others1 he    
examined it by day1 and was enabled to  
follow it  hourly instead of looking at 
it for a short period when near the     
horizon4 ,at length1 after seven years' 
observation1 he announced1 on  ,december
 #h1 #ahhi1 that ,mercury performs only 
one rotation during its  revolution     
round the ,sun--in fact1 that its day   
and year coincide4 ,as a  consequence1  
the planet keeps the same face towards  
the ,sun1 one side  having everlasting  
day and the other perpetual night2 but  
owing to the  libratory movement of     
,mercury--the result of uniform motion  
on its axis  and irregular motion in its
 orbit--the ,sun rises and sets on a    
small zone  of the planet's surface4    
,schiaparelli's observations indicated  

that  ,mercury is a much spotted globe1 
with a moderately dense atmosphere1 and 
he was enabled to form a chart of its   
surface-markings4    ,schiaparelli's    
conclusions remained until #ahif        
unconfirmed and yet not  denied1        
although most astronomers were sceptical
 on the subject4 ,in #ahif  the subject 
was taken up by the ,american           
astronomer1 ,percival ,lowell  7born    
#ahee71 who1 in the clear air of        
,arizona1 confirmed ,schiaparelli's     
conclusions1 fixing #hh days as the     
period of rotation4 ,he remarked1       
however1 that no signs of an atmosphere 
or clouds were visible to him4  ,the    
surface of ,mercury1 he says1 is        
colourless1--8a geography in black  and 
white40 ,the determination of the       
rotation period by ,schiaparelli and    
,lowell is now generally accepted1 and  
is confirmed by the theory of  tidal    
friction4 ,it is only right to add that 
,william ,frederick ,denning  7born     
#ahdh7 in #ahha suspected a rotation    

period of #be hours1 but this  remains  
unconfirmed4 ,in ,april #ahga the       
spectrum of ,mercury was examined  by   
,hermann ,carl ,vogel 7born #ahdb7 at   
,bothkamp4 ,he suspected traces of  an  
atmosphere similar to ours1 but was not 
certain4 ,of more interest are  the     
photometric observations of ,zllner in  
#ahgd4 ,these observations  indicated   
that the surface of ,mercury is rugged  
and mountainous1 and  comparable with   
the ,moon1--a conclusion supported by   
,lowell's  observations in #ahif4       
,venus1 the nearest planet to the       
,earth1 has been attentively studied for
  three centuries1 and still            
comparatively little is known regarding 
it4  ,this is due to its remarkable     
brilliancy1 combined with its proximity 
to  the ,sun4 ,the great problem at the 
beginning of the nineteenth century  was
 the rotation of the planet4 ,in #aggi  
the subject was taken up by  ,schrter at
 ,lilienthal4 ,nine years later1 from a 
faint streak visible on  the disc1 he   

concluded that rotation was performed in
 #bc hours #bh  minutes1 and in #ahaa   
this was reduced by seven minutes2 but  
as ,herschel  was unable to observe the 
markings seen by ,schrter1 many         
astronomers  were inclined to be        
sceptical regarding the accuracy of the 
,lilienthal  observers results4 ,schrter
 also observed the southern horn of     
,venus  when in the crescent form to be 
blunted1 and he ascribed this to the    
existence of a great mountain1 five or  
six times the elevation of  ,chimborazo2
 while he observed irregularities along 
the terminator1 which  he considered to 
be more strongly marked than those on   
the ,moon4  ,schrter's opinion on this  
point1 although rejected by ,herschel1  
was  confirmed by ,mdler1 ,zenger1      
,ertborn1 ,denning1 and by the ,italian 
astronomer ,francesco ,di ,vico         
7#ahje-ahdh71 director of the           
,observatory  of the ,collegio ,romano4 
,in #ahci ,di ,vico attacked the problem
 of the  rotation1 and his results were 

confirmatory of those of ,schrter4 ,he  
estimated that the axis of ,venus was   
inclined at an angle of #ec to the      
plane of its orbit4 ,meanwhile a series 
of important observations had  been made
 on ,venus by the ,scottish astronomer  
and theologian1 ,thomas  ,dick          
7#aggb-aheg71 who suggested daylight    
observations on ,venus to solve  the    
problem of the rotation4    ,in #ahgg   
the question was attacked by            
,schiaparelli1 who commenced a  series  
of observations on ,venus at ,milan in  
that year4 ,the results of  his studies 
were summed up in #ahij in five papers  
contributed to the  ,milan ,academy4 ,he
 came to the conclusion that the        
markings observed by  ,schrter1 ,di     
,vico1 and others were not really       
permanent1 and  concentrated his        
attention on round white spots1 which   
remained fixed in  position4 ,instead of
 observing ,venus in the evening1       
,schiaparelli  followed it by day1      
watching it continuously on one occasion

 for eight  hours4 ,but the markings    
remained fixed4 ,schiaparelli           
accordingly  concluded that the planet's
 rotation was performed in probably #bbe
 days1  equal to the time of revolution4
 ,one face is turned towards the ,sun   
continually1 while the other is         
perpetually in darkness4    ,the        
announcement was so startling that1 as  
,miss ,clerke says1 8a clamour  of      
contradiction was immediately raised1   
and a large amount of evidence  on both 
sides of the question has since been    
collected40 ,perrotin at  ,nice1        
,tacchini at ,rome1 ,cerulli at ,teramo1
 ,mascari at ,catania and ,mount  ,etna1
 and ,lowell in ,arizona1 all in        
favourable climates1 confirmed          
,schiaparelli's results1 as also did a  
second series of observations by  the   
,milan astronomer himself in #ahie4 ,on 
the other hand1 ,neisten1  ,trouvelot1  
,camille ,flammarion 7born #ahdb71 and  
others1 under less  favourable climatic 
conditions1 arrived at a period of #bd  

hours4  ,aristarch ,blopolsky 7born     
#ahed71 from spectroscopic observations 
at  ,pulkowa1 by means of ,doppler's    
principle1 found a period of #ab hours4 
,lowell1 by the same principle1 found1  
in #aija-jc1 a period of #bbe days1  in 
agreement with ,schiaparelli's results4 
,this is the last word on the  subject4 
,schiaparelli's rotation period1        
confirmed by the theory of  tidal       
friction1 is generally accepted4        
,that ,venus has an atmosphere was one  
of the conclusions reached by  ,schrter 
in #agib2 and in this at least he was   
correct1 as the atmosphere  of ,venus1  
illuminated by the solar rays1 has been 
seen extending round  the entire disc of
 the planet4 ,spectroscopic observations
 by ,tacchini1  ,ricco1 and ,young1     
during the transits of #ahgd and #ahhb1 
indicated the  existence of water-vapour
 in the planet's atmosphere4 ,very      
little has  been discovered regarding   
the 8geography0 of ,venus4 ,white       
patches at the  supposed 8poles0 of the 

planet were observed in #ahac by ,franz 
von  ,gruithuisen1 and in #ahgh by the  
,french astronomer ,trouvelot           
7#ahbg-ahie74 ,the secondary light of   
,venus1 similar to the 8old ,moon in    
the new ,moon's arms10 was repeatedly   
observed since the time of ,schrter  by 
,vogel1 ,lohse1 ,zenger1 and others4    
,vogel attributed it to twilight1  and  
,lamp1 a ,german observer1 to electrical
 processes analogous to our  auror4 ,in 
#ahhg a ,belgian astronomer1 ,paul      
,stroobant1 submitted to a  searching   
examination all the supposed            
observations of a satellite of  ,venus1 
and was enabled to explain nearly all   
the supposed satellites as  small stars 
which happened to lie near the planet's 
path in the sky at  the time of         
observation4    ,the study of our own   
planet can hardly be said to belong to  
the realm of  astronomy4 ,nevertheless1 
it is through astronomical observation  
that the  motion of the ,north ,pole has
 been discovered4 ,for many years it has

 been  a problem whether there is a     
variation of latitude resulting from the
  motion of the pole4 ,euler had        
declared1 from theoretical              
investigation1  that1 were there such a 
motion1 the period must be #aj months4  
,the  question was revived in #ahhe by  
the observations of ,seth ,carlo        
,chandler 7born #ahdf7 at ,cambridge1   
,mass41 with his newly-invented         
instrument1 the 8almucantar10 which     
indicated an appreciable variation  of  
latitude4 ,this was confirmed by        
,friedrich ,kstner 7born #ahef71 now    
director of the ,observatory at ,bonn4  
,the idea now occurred to ,chandler  to 
search through the older records to     
discover if there was any trace  of the 
variation of latitude1 with the result  
that he brought out a  period of #ad    
months instead of #aj4 ,this aroused    
much interest1 and many  prominent      
astronomers denied ,chandler's results1 
which were announced in  #ahia4 ,as a   
well-known astronomer has expressed it1 

8,euler's work had  shown what period   
the motion must have1 and any appearance
 of another  period must be due to some 
error in the observations4 ,chandler    
replied  to the effect that he did not  
care for ,euler's mathematics3 the      
observations plainly showed #ad months1 
and if ,euler said #aj1 he must  have   
made the mistake4 ,i do not exaggerate  
the situation in the least2  it was a   
deadlock3 ,chandler and observation     
against the whole weight of  observation
 and theory40 ,it was now shown by      
,newcomb that ,euler had  assumed the   
,earth to be an absolutely rigid body1  
while modern  investigations show that  
it is not so4 ,chandler's discovery is  
now  accepted1 and proves that the      
,north ,pole is not fixed in position1  
but  has a small periodic motion1 though
 never twelve yards from its mean       
position4 ,that the small resulting     
variation in the position of the  stars 
has been noticed at all is a striking   
illustration of the accuracy  of        

astronomical observation4    ,of all the
 planets ,mars has been most studied    
during the nineteenth  century4 ,many   
illustrious astronomers have devoted    
years to the study of  the red planet1  
with the result that more is known of   
the surface of  ,mars than of any other 
celestial body1 with the exception of   
the ,moon4  ,after the time of          
,herschel1 the leading students of ,mars
 were ,beer and  ,mdler1 who carefully  
studied the planet from #ahbh to #ahci4 
,they  identified at each opposition the
 same dark spots1 frequently obscured   
by mists1 and they also made the most   
accurate determination of the  rotation 
period1 which they fixed at #bd hours   
#cg minutes #bc seconds4  ,this estimate
 was confirmed in #ahfb by ,friedrich   
,kaiser 7#ahjh-ahgb7 of  ,leyden1 in    
#ahfi by ,richard ,anthony ,proctor     
7#ahcg-ahhh71 and in #ahib by           
,henricius ,gerardus van de ,sande      
,bakhuyzen 7born #ahch71 director of the
  ,leyden ,observatory4 ,in #ahfb       

,lockyer identified the various markings
 seen  by ,beer and ,madler in #ahcj4   
,the other great names in ,martian study
 prior  to #ahgg are ,angelo ,secchi and
 ,william ,rutter ,dawes 7#agii-ahfh71  
who  studied ,mars from #aheb to #ahfe  
and secured a very valuable series of   
drawings4 ,these drawings were used by  
,proctor for the construction of  the   
first reliable map of ,mars1 which was  
published in #ahgj in his work1         
#8,other ,worlds than ,ours4' ,proctor  
gave names to the various ,martian      
features1 the reddish-ochre portions of 
the disc being named continents  and the
 bluish-green portions seas2 and        
,proctor's views on ,mars found  favour 
for many years4 ,in #ahgg1 however1     
,schiaparelli opened a new era  in the  
study of ,mars4 ,in ,september of that  
year1 during the very  favourable       
opposition of the planet1 ,schiaparelli1
 while executing a  trigonometrical     
survey of the disc1 discovered that the 
continents were  cut up by numerous long

 dark streaks1 which he called canali4  
,in #ahgi1  to his surprise1 he found   
that some of the canals had become      
double2 and  he confirmed this in #ahha 
and at subsequent oppositions4          
,meanwhile1 as  ,schiaparelli was the   
only observer who had hitherto seen the 
canals1  there was much scepticism as to
 their reality4 ,in #ahhf1 however1 they
  were seen at the ,nice ,observatory by
 ,henri ,perrotin 7#ahde-aijd71 who     
also observed their duplication4 ,since 
#ahhf they have been observed by  many  
astronomers1 including ,camille         
,flammarion in ,france1 ,william        
,frederick ,denning 7born #ahdh7 in     
,england1 ,vincenzo ,cerulli 7born      
#ahei7 in ,italy1 ,percival ,lowell and 
,w4 ,h4 ,pickering in the ,united       
,states4 ,in #ahib ,w4 ,h4 ,pickering   
successfully observed the canals1 and   
discovered at the junctions of two or   
more canals round black spots1 to  which
 he gave the name of 8lakes10 in keeping
 with the view that the  dark regions of

 the planet were seas4    ,in #ahid     
,percival ,lowell erected at ,flagstaff1
 ,arizona1 an observatory  for the      
specific purpose of observing ,mars and 
its canals in good and  steady air4 ,he 
was assisted by ,w4 ,h4 ,pickering and  
by ,andrew ,ellicott  ,douglass 7born   
#ahfg74 ,during a year's study ,douglass
 measured the  ,martian atmosphere and  
discovered canals crossing the dark     
regions of  the planet1 finally         
disproving the idea of their aqueous    
character4  ,lowell recognised all      
,schiaparelli's canals1 and discovered  
many more4  ,he also attentively studied
 the south polar cap of ,mars1 which    
disappeared entirely on ,october #ab1   
#ahid4 ,lowell noticed1 also1 that as   
the cap melted the canals became darker1
 as if water was being conveyed  down2  
and accordingly he adopted the view put 
forward by ,schiaparelli1  that the     
canals are waterways lined on either    
side by banks of  vegetation4 ,his      
observations were published in the end  

of #ahie in his  work #8,mars4' ,he is  
of opinion that the reddish-ochre       
regions or  8continents0 are deserts1   
and the greenish areas marshy tracts of 
vegetation4 ,the lakes are named by him 
8oases10 and1 as ,miss ,clerke          
observes1 he 8does not shrink from the  
full implication of the term40 ,he      
regards the canals as strips of         
vegetation fertilised by a small canal1 
much too small to be seen1 an idea which
 originated with ,w4 ,h4  ,pickering4   
,the canals are believed by ,lowell to  
be waterways down which  the water from 
the melting polar cap is conveyed to the
 various oases4  ,he considers1 in fact1
 that the canals are constructed by     
intelligent  beings with the express    
purpose of fertilising the oases1       
regarded by  him as centres of          
population4 ,he remarks that water is   
scarce on the  planet1 owing to its     
small size1 and as a consequence the    
inhabitants  are forced to utilise every
 drop4 ,the canal system is the result4 

,lowell's theory has not been cordially 
received--although it is now  gradually 
gaining popularity1--and several other  
hypotheses have been  propounded to     
explain the canals4 ,proctor1 who died  
some years before  ,lowell's theory was 
given to the world1 regarded them as    
rivers1 but  this view may now be looked
 upon as abandoned4 ,it was suggested   
that the  canals might be cracks in the 
surface of ,mars or meteors ploughing   
tracks above it3 and ,professor ,john   
,martin ,schaeberle 7born #ahec7 of  the
 ,lick ,observatory put forward the view
 that the canals were chains of         
mountains running over the light and    
dark regions4 ,none of these  theories1 
however1 gained popularity1 and had to  
give way to a more  popular theory1 the 
8illusion0 hypothesis1 put forward by   
the ,italian  astronomer ,cerulli1 and  
supported by ,newcomb and ,maunder4 ,on 
the basis  of the illusion theory1      
,newcomb explains that the 8canaliform0 
appearance 8is not to be regarded as a  

pure illusion on the one hand or  an    
exact representation of objects on the  
other4 ,it grows out of the  spontaneous
 action of the eye in shaping slight and
 irregular  combinations of light and   
shade1 too minute to be separately made 
out  into regular forms40 ,experiments  
were made by ,maunder in #aijb1 and the 
results pointed to the truth of the     
theory that the canals were really      
illusions4 ,but the studies of ,lowell  
at the oppositions of #aijc and #aije   
have seriously weakened the hypothesis  
of ,cerulli and ,maunder1 and  strongly 
confirm the theory of the artificial    
origin of the canals4 ,in  #aijc ,lowell
 was enabled1 from a study of the       
development of the canals1  to show the 
probability of their artificial nature1 
and his study of the  double canals     
showed a distinct plan in their         
distribution4 ,finally1 on  ,may #aa1   
#aije1 several photographs of ,mars were
 secured at the ,lowell  ,observatory1  
on which the canals appeared1 not as    

dots of light and  shade1 as on the     
illusion theory1 but as straight dark   
lines4 ,this goes  far to prove the     
reality of the canals1--in spite of the 
ridicule cast on  them and their        
observers1--and consequently the truth  
of the theory of  intelligent life in   
,mars4    ,meanwhile the old-fashioned  
,martian observations have been         
continued in  less favourable climates  
than ,arizona and ,italy by various     
astronomers1  among them the famous     
,camille ,flammarion1 the ,american     
astronomers  ,james ,edward ,keeler     
7#aheg-aijj71 ,edward ,emerson ,barnard 
7born #aheg71  the ,english astronomer  
,w4 ,f4 ,denning1 and others4 ,these    
conscientious  and painstaking observers
 have done much for ,martian study in   
increasing  the number of accurate      
delineations of the ,martian surface4   
,the spectrum of ,mars was first        
examined by ,huggins in #ahfg4 ,he found
  distinct traces of water-vapour1 and  
this was confirmed by ,vogel in  #ahgb1 

and by ,maunder some years later4 ,in   
#ahid1 however1 ,william  ,wallace      
,campbell 7born #ahfb71 the ,american   
astronomer1 observing from  the ,lick   
,observatory1 ,california1 was unable to
 detect the slightest  difference       
between the spectra of ,mars and the    
,moon1 indicating that  ,mars had no    
appreciable atmosphere2 and from this he
 deduced that the  ,martian polar caps  
could not be composed of snow and ice1  
but of frozen  carbonic acid gas4 ,in   
#ahie1 however1 ,vogel confirmed his    
previous  observations1 and reaffirmed  
the presence of water-vapour in the     
,martian  atmosphere4    ,during the    
opposition of #ahcj1 ,mdler undertook an
 extensive search for  a ,martian       
satellite1 but was unsuccessful4 ,in    
#ahfb the search was  resumed by        
,heinrich ,louis ,d',arrest             
7#ahbb-ahge71 the famous ,german        
observer1 who was also unsuccessful4    
,accordingly the red planet was         
referred to by ,tennyson as the         

8moonless ,mars40 ,in #ahgg the search  
was  taken up by ,asaph ,hall1 the      
self-made ,american astronomer1 born at 
,goshen1 ,connecticut1 in #ahbi1 and    
employed from #ahfb to #ahia at the     
,naval ,observatory1 ,washington4       
,during the famous opposition of ,august
  #ahgg1 favoured by the great #bf-;inch
 refractor1 he succeeded in  discovering
 two very small satellites of ,mars1 to 
which he gave the  names of ,phobos and 
,deimos4 ,he determined the time of     
revolution of  ,phobos at #g hours #ci  
minutes1 and that of ,deimos at #cj     
hours #ag  minutes1--,phobos revolving  
round ,mars more than three times for   
one  rotation of the planet on its axis4
 ,these two satellites are very small1  
not more than thirty miles in diameter4 
,after ,hall's successful search1       
photographs were exposed at the ,paris  
,observatory for other ,martian         
satellites1 but none was discovered4 ,no
 further moons have been found          
belonging to the red planet1 nor is it  

likely that any further  satellites of  
,mars are in existence4    ,the         
discovery of a zone of small planets in 
the space between ,mars and  ,jupiter   
belongs completely to the nineteenth    
century1 although the  existence of a   
planet in the vacant space was suspected
 three centuries  ago4 ,in #aggb the    
subject was taken up by ,johann ,elert  
,bode  7#agdg-ahbf71 afterwards director
 of the ,berlin ,observatory1 who       
investigated a curious numerical        
relationship1 since known as ,bode's    
,law1 connecting the distances of the   
planets4 ,if four is added to each  of  
the numbers--#j1 #c1 #f1 #ab1 #bd1 #dh1 
#if1 and #aib1 the resulting series     
represents pretty accurately the        
distances of the planets from the ,sun1 
thus--#d 7,mercury71 #g 7,venus71 #aj   
7,the ,earth71 #af 7,mars71 #bh1 #eb1   
7,jupiter71 and #ajj 7,saturn74 ,after  
the discovery of ,uranus1 in #agha1 it  
was found that it filled up the number  
#aif4 ,bode1 however1 saw that the      

number #bh1 between ,mars and ,jupiter1 
was vacant1 and predicted the  discovery
 of the planet4 ,aided by ,franz ,xavier
 von ,zach 7#aged-ahcb71  he called a   
congress of astronomers1 which assembled
 in #ahjj at  ,schrter's observatory at 
,lilienthal1 when1 for the purpose of   
searching  for the missing planet1 the  
zodiac was divided into twenty-four     
zones1  each of which was given to a    
separate astronomer4 ,one of them was   
reserved for ,giuseppe ,piazzi          
7#agdf-ahbf71 director of the           
,observatory  of ,palermo4    ,born in  
#agdf at ,ponte1 in ,lombardy1 ,giuseppe
 ,piazzi1 after entering the  ,theatine 
,order of monks1 became in #aghj        
,professor of ,mathematics at  ,palermo1
 where an observatory was erected in    
#agia2 and at that  observatory ,piazzi 
worked till his death in #ahbf4 ,in     
#agib he commenced a  great             
star-catalogue1 and while making his    
nightly observations he  discovered1 on 
,january #a1 #ahja--the first night of  

the nineteenth  century1--what he took  
to be a tailless comet1 but which proved
 to be a  small planet revolving round  
the sun in the vacant space4 ,the       
discovery  was hailed by ,bode and ,von 
,zach with much enthusiasm1 and ,piazzi 
named  the planet ,ceres4 ,the little   
planet was1 however1 soon lost in the   
rays  of the sun before sufficient      
observations had been made2 but the     
great  mathematician1 ,friedrich ,gauss 
7#aggg-ahee71 came to the rescue1 and   
pointed out the spot where the planet   
was to be rediscovered4 ,in that  spot  
it was found on ,december #ca1 #ahja1 by
 ,von ,zach at ,gotha1 and on the       
following evening by ,heinrich ,olbers  
7#ageh-ahdj7 at ,bremen4    ,on ,march  
#bh1 #ahjb1 while observing ,ceres from 
his house at ,bremen1  ,olbers was      
struck by the presence of a strange     
object near the path of  the planet4 ,at
 first he supposed it to be a variable  
star at maximum  brilliance1 but a few  
hours showed him that it was in motion1 

and was  therefore another planet4 ,he  
named it ,pallas1 and propounded the    
theory  that the two 8,asteroids0--so   
named by ,herschel--were fragments of a 
trans-,martian planet1 which1 through   
some accident1 had been shattered  to   
pieces in the remote past4 ,olbers urged
 the necessity of searching  for more   
small planets4 ,his advice was taken4   
,in #ahjd ,karl ,ludwig  ,harding       
7#agfe-ahcd71 ,schrter's assistant1     
discovered ,juno1 and ,olbers  himself  
detected ,vesta1 ,march #bi1 #ahjg4     
,after #ahaf the search was             
relinquished1 as no more planets were   
discovered4 ,in #ahcj1 however1 a       
,german amateur1 ,karl ,ludwig ,hencke  
7#agic-ahff71 ex-postmaster of          
,driessen1 commenced a search for new   
planets1 which was rewarded1 after      
fifteen years1 by the discovery of      
,astra1 ,december #h1 #ahde4 ,on ,july  
#a1 #ahdg1 he made another discovery1   
that of ,hebe4 ,a few weeks later1 ,john
 ,russell ,hind 7#ahbc-ahie71 the       

,english astronomer1 discovered ,iris4  
,since #ahdg not a year has passed      
without one or more planets being found1
 sometimes as many as twenty  being     
discovered in a single year4 ,some      
astronomers have made the search  for   
asteroids their chief business4 ,the    
principal asteroid discoverers  have    
been ,christian ,h4 ,f4 ,peters         
7#ahac-ahij71 ,henri ,perrotin1 ,paul   
,henry 7#ahdh-aije71 ,prosper ,henry    
7#ahdi-aijc71 ,james ,watson1 ,robert   
,luther 7#ahbb-aijj71 ,johann ,palisa   
7born #ahdh71 and ,max ,wolf 7born      
#ahfc74    ,in #ahia a new impulse was  
given to asteroid study by the          
application of  photography by ,max     
,wolf to the discovery of the minor     
planets4 ,it  occurred to ,wolf that the
 asteroid would be represented on the   
plate by  a trail1 caused by its motion 
during the time of exposure2 and        
assisted  by ,arnold ,schwassmann 7born 
#ahgj71 ,luigi ,carnera 7born #ahge71   
and  others1 ,wolf has discovered over a

 hundred asteroids1 and he has the      
whole field of asteroid hunting to      
himself4 ,few minor planets are now     
discovered by the older method4 ,in     
#aija ,wolf invented his new instrument 
of research1 the stereo-comparator1     
which1 on the principle of the          
old-fashioned stereoscope1 represents   
the planetary bodies as suspended  in   
space far in front of the stars4 ,in    
this way this ingenious  astronomer has 
been enabled to discover asteroids at   
the first glance3  year by year fresh   
discoveries are announced from the      
,heidelberg  ,observatory1 until more   
than five hundred asteroids are now     
known4    ,waning interest in the       
ever-increasing family of asteroids was 
revived  in #ahih by the discovery by   
,karl ,gustav ,witt 7born #ahff7 of a   
small  planet1 to which he gave the name
 of ,eros1 which comes nearer to the    
,earth than ,mars1 and which is of great
 assistance to astronomers in the       
determination of the solar parallax4    

,for some time prior to #ahih           
astronomers had considered it a waste of
 time to search for new  asteroids2 but 
this idea is not now so popular1 in view
 of the benefit  conferred on astronomy 
by the discovery of ,eros4    ,of the   
physical nature of the asteroids        
astronomers know nothing4 ,only  the    
four largest have been measured4 ,for   
many years it was supposed that  ,vesta1
 the brightest of the asteroids1 was    
also the largest4 ,the  measures of     
,barnard with the great ,lick refractor 
in #ahie1 however1  showed that ,ceres  
is the largest1 with a diameter of #dgg 
miles4 ,pallas  comes next1 with a      
diameter of #cjd miles2 while the       
diameters of ,vesta  and ,juno are      
respectively #bci and #abj miles4       
,barnard saw no traces of  atmosphere   
round any of the asteroids4 ,it should  
be stated that in #ahgb  ,vogel thought 
he could detect an 8air-line0 in the    
spectrum of ,vesta3 he  admitted that   
the observation required confirmation1  

but it has not been  corroborated either
 by himself or any other observer4      
,,chapter ,,vi4                         
,,the ,,outer ,,planets4      ,jupiter1 
the greatest planet of the ,solar       
,system1 has perhaps been more          
persistently studied by astronomers than
 any other4 ,in the early  nineteenth   
century the prevalent idea was that     
,jupiter was a world  similar to the    
,earth1 only much larger1--a view held  
by ,herschel and  other famous          
astronomers1 and put forward by         
,brewster in #8,more ,worlds  than      
,one4' ,this view prevailed for many    
years1 although ,buffon in #aggh1  and  
,kant in #aghe1 had stated their belief 
in the idea that ,jupiter was  still in 
a state of great heat--in fact1 that the
 great planet was a  semi-sun4 ,this    
idea1 however1 was long in being adopted
 by astronomers1  and very little       
attention was paid to ,nasmyth's        
expression of the same  opinion in      
#ahec4 ,the older view still held the   

field--namely1 that the  belts of       
,jupiter represented trade-winds1 and   
that a world similar to  the terrestrial
 lay below the ,jovian clouds4 ,in #ahfj
 ,george ,philip  ,bond 7#ahbf-ahfe71   
director of the ,harvard ,observatory1  
found from  experiments that ,jupiter   
seemed to give out more light than it   
received1  but he did not dare to       
suggest that ,jupiter was self-luminous1
  considering that the inherent light   
might result from ,jovian auroras4      
,in #ahfe ,zllner showed that the rapid 
motions of the cloud-belts on both      
,jupiter and ,saturn indicated a high   
internal temperature4 ,at the  distance 
of ,jupiter sun-heat is only one        
twenty-seventh as great as on  the      
,earth1 and would be quite incapable of 
forming clouds many times  denser than  
those on the ,earth4 ,in #ahga ,zllner  
drew attention to the  equatorial       
acceleration of ,jupiter1 analogous to  
the same phenomenon on  the ,sun4 ,in   
#ahgj these opinions of ,zllner's were  

adopted and supported  by ,proctor in   
his #8,other ,worlds than ,ours4' ,in   
his subsequent volumes  ,proctor did    
much to popularise the idea1 which is   
now accepted all over  the astronomical 
world4    ,during the century many      
valuable observations on ,jupiter were  
made by  numerous observers1 among them 
,airy1 ,mdler1 ,webb1 ,schmidt1 and     
others4  ,much time was devoted to the  
accurate determination of the rotation  
period1 which was fixed at #i hours #ee 
minutes #cfef seconds by ,denning  in   
observations from #ahhj to #aijc4 ,no   
really important discovery was  made    
till #ahgh1 when ,niesten at ,brussels  
discovered the 8great red  spot10 a     
ruddy object #be1jjj miles long by #gjjj
 broad1 attached to a  white zone       
beneath the southern equatorial belt4   
,this remarkable object  has been       
observed ever since4 ,in #ahgi its      
colour was brick-red and very           
conspicuous1 but it soon began to fade1 
and ,ricc's observation at  ,palermo in 

#ahhc was thought to be the last4 ,after
 some months1 however1  it brightened   
up1 and1 notwithstanding changes of form
 and colour1 it is  still visible1 a    
permanent feature of the ,jovian disc4  
,in #ahgi a group  of 8facul10 similar  
to those on the ,sun1 was observed at   
,moscow by  ,theodor ,alexandrovitch    
,brdikhine 7#ahca-aijd71 and at ,potsdam
 by  ,wilhelm ,oswald ,lohse 7born      
#ahde74 ,it was soon observed that the  
rotation period1 as determined from the 
great red spot1 was not  constant1 but  
continually increasing4 ,a white spot in
 the vicinity  completed its rotation in
 #e minutes less1 indicating the        
differences of  rotation on ,jupiter4   
,the great red spot has been observed   
since its discovery by ,denning at      
,bristol and ,george ,hough 7born #ahcf7
 at ,chicago4 ,twenty-eight years of    
observation have not solved the mystery 
of its nature4 ,the researches  made on 
it1 in the words of ,miss ,clerke1      
8afforded grounds only for  negative    

conclusions as to its nature4 ,it       
certainly did not represent  the        
outpourings of a ,jovian volcano2 it was
 in no sense attached to the  ,jovian   
soil--if the phrase have any application
 to the planet2 it was not  a mere      
disclosure of a glowing mass elsewhere  
seethed over by rolling  vapours40      
,in #ahgj ,arthur ,cowper ,ranyard      
7#ahde-ahid71 the well-known ,english   
astronomer1 began to collect records of 
unusual phenomena on the ,jovian  disc  
to see if any period regulated their    
appearance4 ,he came to the  conclusion 
that1 on the whole1 there was harmony   
between the markings on  ,jupiter and   
the eleven-year period on the ,sun4 ,the
 theory of inherent  light in ,jupiter1 
however1 has not been confirmed4 ,the   
great planet was  examined              
spectroscopically by ,huggins from #ahfb
 to #ahfd1 and by ,vogel  from #ahga to 
#ahgc4 ,the spectrum showed1 in addition
 to the lines of  reflected sunlight1   
some lines indicating aqueous vapour1   

and others  which have not been         
identified with any terrestrial         
substance4 ,a  photographic study of the
 spectrum of ,jupiter was made at the   
,lowell  ,observatory by ,slipher in    
#aijd1 probably the most exhaustive     
investigation on the subject4 ,the      
spectroscope has1 however1 given  little
 support to the theory of inherent      
light1 and 8we are driven to  conclude  
that native emissions from ,jupiter's   
visible surface are local  and fitful1  
not permanent and general40             
,herschel's idea1 that the rotations of 
the four satellites of ,jupiter  were   
coincident with their revolutions1 has  
on the whole been confirmed  by recent  
researches1 although in the case of the 
two near satellites  7,io and ,europa7  
,w4 ,h4 ,pickering's observations in    
#ahic indicated shorter  rotation       
periods4 ,there is much to learn        
regarding the geography of the          
satellites1 although in #ahia           
,schaeberle and ,campbell at the ,lick  

,observatory observed belts on the      
surface of ,ganymede1 the third         
satellite analogous to those on         
,jupiter4 ,surface-markings on the      
satellites have also been seen by       
,barnard at the ,lick ,observatory1 and 
by ,douglass at ,flagstaff4    ,since   
the time of ,galileo no addition had    
been made to the system of  satellites  
revolving round ,jupiter4 ,profound     
surprise was created1  therefore1 by the
 announcement of the discovery of a     
fifth satellite by  ,barnard at the     
,lick ,observatory1 on ,september #i1   
#ahib4 ,the satellite1  one of the      
faintest of telescopic objects1 was     
discovered with the great  #cf-;inch    
telescope1 and its existence was soon   
confirmed by ,andrew  ,anslie ,common   
7#ahda-aijc71 with his great #e-;foot   
reflector at ,ealing1  near ,london4    
,the new satellite was found by ,barnard
 to revolve round  ,jupiter in #aa hours
 #eg minutes at a mean distance of      
#aab1jjj miles4    ,although the        

existence of other satellites of        
,jupiter was predicted by  ,sir ,robert 
,stawell ,ball 7born #ahdj7 soon after  
the discovery of the  fifth1 much       
surprise was created by the             
announcement1 in ,january #aije1  that a
 sixth satellite had been discovered by 
,perrine1 who1 in the  following month1 
announced the discovery of a seventh4   
,these discoveries  were made by        
photography1 the objects being very     
faint4 ,the periods of  revolution were 
found to be #bdb days and #bjj days for 
the sixth and  seventh satellites       
respectively1 the mean distances being  
#f1ifh1jjj and  #f1acf1jjj miles4 ,it is
 possible that they may belong to a zone
 of  asteroidal satellites4 ,in fact1   
the fifth moon may belong to a similar  
zone1 so that ,jupiter may have two     
asteroidal zones2 but this is           
anticipating future discovery4    ,a    
particular charm has always attached    
itself to the study of ,saturn1  the    
ringed planet4 ,the magnificent system  

of rings has for two and a  half        
centuries been the object of wonder and 
admiration in the ,solar  ,system1 and  
accordingly they have been exhaustively 
studied by many  eminent observers4     
,while observing the two bright rings of
 ,saturn on  ,june #aj1 #ahch1 ,galle   
noticed what ,miss ,clerke calls 8a     
veil-like  extension of the lucid ring  
across half the dark space separating it
  from the planet40 ,no attention1      
however1 was paid to ,galle's           
observation4 ,on ,november #ae1 #ahej1  
,william ,cranch ,bond 7#aghi-ahei71 of 
the ,harvard ,observatory in            
,massachusetts1 discovered the same     
phenomenon  under its true form--that of
 a dusky ring interior to the more      
brilliant  one4 ,a fortnight later1     
before the news of ,bond's observation1 
,dawes  made the same discovery         
independently at ,wateringbury in       
,england4 ,this  ring is known as the   
dusky or 8crape0 ring4    ,the discovery
 of the dusky ring brought to the front 

the problem of the  composition of the  
ring-system4 ,laplace and ,herschel     
considered the  rings to be solid1 but  
this was denied in #ahdh by ,edouard    
,roche  7#ahbj-ahhj71 who believed them 
to consist of small particles1 and in   
#ahea by ,g4 ,p4 ,bond1 who asserted    
that the variations in the appearance   
of the system were sufficient to        
negative the idea of their solidity2    
but he suggested that the rings were    
fluid4 ,in #aheg the question was  taken
 up by the ,scottish physicist1 ,james  
,clerk-,maxwell 7#ahca-ahgi71  who      
proved by mathematical calculation that 
the rings could be neither  solid nor   
fluid1 but were due to an aggregation of
 small particles1 so  closely crowded   
together as to present the appearance of
 a continuous  whole4 ,clerk-,maxwell's 
explanation--which had been suggested by
 the  younger ,cassini in #agae1 and by 
,thomas ,wright in #agej--was at once   
adopted1 and has since been proved by   
observation4 ,in #ahhh ,hugo  ,seeliger 

7born #ahdi71 director of the ,munich   
,observatory1 showed from  photometric  
observations the correctness of the     
satellite-theory2 while  ,barnard in    
#ahhi witnessed an eclipse of the       
satellite ,japetus by the  dusky ring4  
,the satellite did not disappear1 but   
was seen with perfect  distinctness4    
,the final demonstration of the meteoric
 nature of the  rings was made by       
,keeler at the ,alleghany ,observatory  
in #ahie1 with the  aid of the          
spectroscope4 ,by means of ,doppler's   
principle1 he found that  the inner edge
 of the ring revolved in a much shorter 
time than the  outer1 proving           
conclusively that they could not be     
solid4 ,this was  confirmed by the      
observations of ,campbell at ,mount     
,hamilton1 ,henri  ,deslandres at       
,meudon1 and ,blopolsky at ,pulkowa4    
,in #ahea a startling theory regarding  
,saturn's rings was put forward by  the 
famous ,otto ,wilhelm von ,struve       
7#ahai-aije74 ,comparing his            

measurements on the rings made at       
,pulkowa in #ahej and #ahea with those  
of  other astronomers for the past two  
hundred years1 he reached the           
conclusion that the inner diameter of   
the ring was decreasing at the  rate of 
sixty miles a-year1 and that the bodies 
composing the rings were  being drawn   
closer to the planet4 ,accordingly1     
,struve calculated that  only three     
centuries would be required to bring    
about the precipitation  of the         
ring-system on to the globe of ,saturn4 
,in #ahha and #ahhb ,struve1  expecting 
a further decrease1 made another series 
of measures1 but these  did not confirm 
his theory1 which was accordingly       
abandoned4    ,the study of the globe of
 ,saturn has made less progress than    
that of the  rings4 ,the surface of the 
planet had been known since before the  
time of  ,herschel to be covered with   
belts1 but as spots seldom appear on    
,saturn1  only one determination of the 
rotation period had been made1 that by  

,herschel4 ,much interest was aroused1  
therefore1 by the discovery1 by  ,hall1 
at ,washington1 on ,december #g1 #ahgf1 
of a bright equatorial spot4  ,hall     
studied this spot during sixty rotations
 of the planet1 determining  the period 
as #aj hours #ad minutes #bd seconds4   
,this was confirmed by  ,denning in     
#ahia1 and by ,stanley ,williams1 an    
,english observer1 in the  same year4   
,on ,june #af1 #aijc1 ,barnard1 at the  
,yerkes ,observatory1  discovered a     
bright spot1 from which he deduced a    
rotation period of #aj  hours #ci       
minutes1--a period considerably longer  
than that found by ,hall4  ,in the same 
year various spots on ,saturn were      
observed by ,denning1 who  found a      
period of #aj hours #cg minutes #efd    
seconds1 and at ,barcelona by  ,jos     
,comas ,sola1 now director of the       
,observatory there1 who may be          
considered ,spain's leading astronomer4 
,the result of these observations  has  
been to show that the spots on ,saturn  

have probably a proper motion  of their 
own1 apart from the rotation of the     
planet4 ,as to the spectrum  of ,saturn1
 little has been learned4 ,it closely   
resembles that of  ,jupiter4 ,in #ahfg  
,janssen1 observing from the summit of  
,mount ,etna1 found  traces of aqueous  
vapour in the planet's atmosphere4      
,in the chapters on ,herschel we have   
seen that he discovered the sixth  and  
seventh satellites of ,saturn4 ,the next
 discovery was made on  ,september #ai1 
#ahdh1 by ,w4 ,c4 ,bond1 at ,harvard1   
,massachusetts1 and  independently by   
,william ,lassell 7#agii-ahhj71 at      
,starfield1 near  ,liverpool4 ,the new  
satellite received the name of          
,hyperion1 and was  found to be situated
 at a distance of about #idf1jjj miles  
from ,saturn4  ,its small size led ,sir 
,john ,herschel to the idea that it     
might be an  asteroidal satellite4      
,fifty years elapsed before another     
satellite of  ,saturn was discovered4   
,in #ahhh ,w4 ,h4 ,pickering commenced a

 photographic  search for new satellites
 of the planet4 ,at last1 on developing 
some  photographs of ,saturn1 taken on  
,august #af1 #ag1 and #ah1 #ahih1 he    
found  traces of a new satellite which  
he named 8,phbe40 ,but1 as the satellite
  was not seen or photographed again for
 some years1 many astronomers were      
sceptical as to its existence4 ,however1
 photographs taken in #aijj1 #aija1  and
 #aijb revealed the satellite1 which was
 again photographed in #aijd1  and seen 
visually by ,barnard in the same year   
with the #dj-;inch ,yerkes  telescope4  
,at that time the discoverer brought out
 the amazing fact that  the motion of   
the satellite is retrograde--a fact     
which he attempts to  explain by a new  
theory of the former rotation of        
,saturn4 ,he likewise  demonstrated that
 its distance from ,saturn varied from  
#f1abj1jjj to  #i1gdj1jjj miles4 ,early 
in #aije ,pickering announced the       
discovery of a  tenth satellite of      
,saturn1 which received the name of     

,themis1 with a  period and mean        
distance nearly similar to ,hyperion1 so
 that ,sir ,john  ,herschel's idea of   
,hyperion being an asteroidal satellite 
is being  confirmed after a lapse of    
half a century4    ,if little is known  
of the globe of ,saturn1 still less is  
known regarding  ,uranus4 ,dusky bands  
resembling those of ,jupiter were       
observed by ,young  at ,princeton in    
#ahhc4 ,in the following year ,paul and 
,prosper ,henry  discerned at ,paris two
 grey parallel lines on the disc of the 
planet4  ,this was confirmed by the     
observations of ,perrotin at ,nice1     
which also  indicated rotation in a     
period of ten hours4 ,in #ahij ,perrotin
 again took  up the study and           
re-observed the dark bands4 ,on the     
other hand1 no  definite results        
regarding the planet were obtained by   
the ,lick  observers in #ahhi and #ahij4
 ,measurements of the planet by ,young1 
,schiaparelli1 ,perrotin1 and others    
indicate a considerable polar           

compression4 ,the spectrum of the planet
 has been studied by ,secchi1  ,huggins1
 ,vogel1 ,keeler1 ,slipher1 and others4 
,the spectrum shows six  bands of       
original absorption1 a line of hydrogen1
 which1 says ,miss  ,clerke1 8implies   
accordingly the presence of free        
hydrogen in the  ,uranian atmosphere1   
where a temperature must thus prevail   
sufficiently  high to reduce water to   
its constituent elements40 ,from a      
photographic  study of the spectrum at  
the ,lowell ,observatory in #aijd1      
,slipher  observed a line corresponding 
to that of helium1 indicating the       
presence  of that element in the        
planet's atmosphere4    ,herschel left  
our knowledge of the ,uranian satellites
 in a very  uncertain state4 ,the two   
outer satellites1 ,titania and ,oberon1 
were  rediscovered in #ahbh by his son1 
but the other four1 which he was        
believed to have discovered1 were never 
seen again4 ,in #ahdg two inner         
satellites1 ,ariel and ,umbriel1 were   

discovered by ,lassell and ,otto        
,struve respectively1 their existence   
being finally confirmed by  ,lassell's  
observations in #ahea4    ,after the    
discovery of ,uranus by ,herschel1      
mathematical astronomers  determined its
 orbit and calculated its position in   
the future4 ,alexis  ,bouvard1 the      
calculating partner of ,laplace1        
published tables of the  planet's       
motions1 founded on observations made by
 various astronomers  who had considered
 it a star before its discovery by      
,herschel2 but as  the planet was not in
 the exact position which ,bouvard      
predicted1 he  rejected the earlier     
observations altogether4 ,for a few     
years the planet  conformed to the      
,frenchman's predictions1 but shortly   
afterwards it was  again observed to    
move in an irregular manner1 and the    
discrepancy  between observation and the
 calculations of mathematicians became  
intolerable4 ,did the law of gravitation
 not hold good for the frontiers  of the

 ,solar ,system8 ,gradually astronomers 
arrived at the conclusion  that ,uranus 
was being attracted off its course by   
the influence of an  unseen body1 an    
exterior planet4 ,bouvard himself was   
one of the first to  make the           
suggestion1 but died before the planet  
was discovered4 ,an  ,english amateur1  
the ,rev4 ,t4 ,j4 ,hussey1 resolved to  
make1 in #ahcd1 a  determination of the 
place of the unseen body1 but found his 
powers  inadequate2 and in #ahdj ,bessel
 laid his plans for an investigation of 
the problem1 but failing health         
prevented him carrying out his design4  
,in #ahda a student at the ,university  
of ,cambridge resolved to grapple  with 
the problem4 ,john ,couch ,adams1 born  
at ,lidcot in ,cornwall in #ahai1       
entered in #ahci the ,university of     
,cambridge1 where he graduated in #ahdc4
  ,from #aheh ,professor of ,astronomy  
at ,cambridge1 and from #ahfa director  
of  the ,observatory1 he died on        
,january #ba1 #ahib1 after a life spent 

in  devotion to mathematical astronomy4 
,in #ahdc1 on taking his degree1 he     
commenced the investigation of the orbit
 of ,uranus4 ,for two years he  worked  
at the difficult question1 and by       
,september #ahde came to the  conclusion
 that a planet revolving at a certain   
distance beyond ,uranus  would produce  
the observed irregularities4 ,he handed 
to ,james ,challis  7#ahjc-ahhb71 the   
director of the ,cambridge ,observatory1
 a paper  containing the elements of    
what was named by ,adams 8the new       
planet40 ,on  ,october #ba of the same  
year he visited ,greenwich ,observatory1
 and left a  paper containing the       
elements of the planet1 and             
approximately fixing  its position in   
the heavens4 ,but the ,astronomer-,royal
 of ,england1 ,sir  ,george ,biddell    
,airy 7#ahja-ahib71 had little faith in 
the calculations  of the young          
mathematician4 ,he always considered the
 correctness of a  distant mathematical 
result to be a subject rather of moral  

than of  mathematical evidence3 in fact1
 regarding ,uranus1 the                 
,astronomer-,royal  almost called in    
question the correctness of the law of  
gravitation4  ,besides1 the novelty of  
the investigations aroused scepticism1  
and the  fact that ,adams was a young   
man1 and inexperienced1 went against    
,airy's  acceptance of the theory4      
,however1 he wrote to ,adams questioning
 him on  the soundness of his idea4     
,adams thought the matter trivial1 and  
did not  reply4 ,airy1 therefore1 took  
no interest in the investigations1 and  
no  steps were taken to search for the  
unseen planet4 ,meanwhile the ,rev4 ,w4 
,r4 ,dawes happened to see ,adams'      
papers lying at ,greenwich1 and wrote to
  his friend1 the well-known astronomer 
,lassell1 who was in possession of  a   
very fine reflector1 erected at his     
residence near ,liverpool1 asking  him  
to search for the planet4 ,but ,lassell 
was suffering from a sprained  ankle1   
and ,dawes' letter was accidentally     

destroyed by a housemaid4 ,so  ,adams'  
theory remained in obscurity4    ,the   
question now came under the notice of   
,franois ,jean ,dominique  ,arago       
7#aghf-ahec71 the director of the ,paris
 ,observatory4 ,he recognised  in a     
young friend of his a rising genius1 who
 was competent to solve the  problem4   
,urban ,jean ,joseph ,le ,verrier1 born 
at ,saint ,lo1 in ,normandy1 in  #ahaa1 
became in #ahcg astronomical teacher in 
the cole ,polytechnique1  and in #ahec  
director of the ,paris ,observatory4 ,in
 consequence of  differences with his   
staff he was obliged1 in #ahgj1 to      
resign from this  position1 but two     
years later was restored to the post1   
which he held  till his death on        
,september #bc1 #ahgg4    ,in #ahde1    
ignorant of the fact that ,adams had    
already solved the problem1  ,le        
,verrier began his investigations of the
 irregular motions of ,uranus4  ,in a   
memoir communicated to the ,academy of  
,sciences in ,november of that  year1 he

 demonstrated that no known causes could
 produce these  disturbances4 ,in a     
second memoir1 dated ,june #a1 #ahdf1 he
 announced that  an exterior planet     
alone could produce these effects4 ,but 
,le ,verrier had  now before him the    
difficult task of assigning an          
approximate position  to the unseen     
body1 so that it might be telescopically
 discovered4 ,after  much calculation   
,le ,verrier1 in his third memoir       
7,august #ca1 #ahdf71  assigned to the  
planet a position in the constellation  
,aquarius4    ,meanwhile one of ,le     
,verrier's papers happened to reach     
,airy4 ,seeing its  resemblance to      
,adams' papers1 which had been lying on 
his desk for  months1 his scepticism    
vanished1 and he suggested to ,challis  
that the  planet should be searched for 
with the ,cambridge equatorial4 ,in     
,july  #ahdf the search was commenced4  
,the planet was actually observed on    
,august #d and #ab1 but1 owing to the   
absence of star maps1 it was not        

recognised4 8,after four days of        
observing10 he wrote to ,airy1 8the     
planet was in my grasp if ,i had only   
examined or mapped the  observations40  
,le ,verrier wrote to ,encke1 the       
illustrious director of the ,berlin     
,observatory1 desiring him to make a    
telescopic search for a planetary       
object situated in the constellation    
,aquarius1 as bright as a star of  the  
eighth magnitude and possessed of a     
visible disc4 8,look where ,i tell      
you10 wrote the ,french astronomer1 8and
 you will see an object such as ,i      
describe40 ,encke ordered his two       
assistants1 ,galle and ,d',arrest1 to   
make  a search on the night of          
,september #bc1 #ahdf4 ,in a few hours  
,galle  observed an object not marked in
 the star-maps of the ,berlin           
,observatory1 which had been recently   
published4 ,the following night         
sufficed to show that the object was in 
motion1 and was therefore a new  planet4
 ,on ,september #bi ,challis found the  

planet at ,cambridge1 but he  was too   
late1 as the priority of the discovery  
was now lost to ,adams4  ,the planet    
received the name of 8,neptune40    ,for
 some time1 indeed1 it appeared as if   
the ,french astronomer alone was  to    
receive the honour of the discovery4    
,but on ,october #c1 #ahdf1 a letter    
from ,sir ,john ,herschel appeared in   
the #8,athenum' in which he referred  to
 the discovery made by ,adams4 ,the     
,french scientists were extremely       
jealous4 ,indeed1 ,arago actually       
declared that1 when ,neptune was under  
discussion1 the entire honour should go 
to ,le ,verrier1 and the name of  ,adams
 should not even be mentioned1--,arago's
 line of reasoning being that  it was   
not the man who first made a discovery  
who should receive the  credit1 but he  
who first made it public4 ,however1 the 
credit of the  discovery is now given   
equally to ,adams and ,le ,verrier1 both
 of whom are  regarded as among the     
greatest of astronomers4    ,only a     

fortnight after the discovery of        
,neptune1 the astronomer ,lassell       
observed a satellite to the distant     
planet on ,october #aj1 #ahdf4 ,this    
discovery was confirmed in ,july #ahdg  
by the discoverer himself1 and  shortly 
afterwards by ,bond and ,otto ,struve4  
,regarding the globe of  ,neptune1 we   
know practically nothing4 ,no markings  
of any kind have been  observed on its  
surface4 ,however1 in #ahhc and #ahhd1  
,maxwell ,hall1 an  astronomer in       
,jamaica1 noticed certain variations of 
brilliance which  suggested a           
rotation-period of eight hours1 but this
 was not confirmed  by any other        
astronomer4 ,the spectrum of ,neptune   
has been investigated  by various       
observers1 who have found it to be      
similar to that of ,uranus4    ,the     
existence of a trans-,neptunian planet  
has been suspected by many  astronomers4
 ,in ,november #ahgi the first idea of  
its existence was thrown  out by        
,flammarion in his #8,popular           

,astronomy4' ,flammarion noticed that   
all the periodical comets in the ,solar 
,system have their aphelion near  the   
orbit of a planet4 ,thus ,jupiter owns  
about eighteen comets2 ,saturn  owns    
one1 and probably two2 ,uranus two or   
three2 and ,neptune six4 ,the  third    
comet of #ahfb1 however1 along with the 
,august meteors1 goes  farther out than 
the orbit of ,neptune4 ,accordingly1    
,flammarion suggested  the existence of 
a great planet1 assigning it a period of
 #ccj years and  a distance of #djjj    
millions of miles4    ,two independent  
investigators1 ,david ,peck ,todd 7born 
#ahee7 in ,america  and ,george ,forbes 
in ,scotland1 have since undertaken to  
find the  planet4 ,todd1 utilising the  
8residual perturbations0 of ,uranus1    
assigned  a period of #cge years for his
 planet4 ,forbes1 on the other hand1    
working  from the comet theory1 stated  
his belief in the existence of two      
planets  with periods of #ajjj and #ejjj
 years respectively4 ,in ,october #aija 

he  computed the position of the new    
planet on the celestial sphere1 fixing  
its position in the constellation       
,libra1 and computing its size to be    
greater than ,jupiter4 ,a search was    
made by means of photography1 in  #aijb1
 but without success4 ,nevertheless1    
astronomers are pretty  confident of the
 existence of one or more               
trans-,neptunian planets4  ,lowell is   
very definite on this subject when he   
says in regard to meteor  groups1 8,the 
,perseids and the ,lyrids go out to meet
 the unknown planet1  which circles at a
 distance of about forty-five           
astronomical units from  the ,sun4 ,it  
may seem strange to speak thus          
confidently of what no mortal  eye has  
seen1 but the finger of the sign-board  
of phenomena points so  clearly as to   
justify the definite article4 ,the eye  
of analysis has  already suspected the  
invisible40                             
,,chapter ,,vii4                        
,,comets4      ,at the time of ,herschel

 the ancient superstitions in regard to 
comets  had to a great extent vanished1 
thanks mainly to the return of ,halley's
  comet in #ageh4 ,yet1 although comets 
had ceased to be objects of terror1  no 
explanation or rational theory of their 
nature was put forward until  the       
appearance of the great comet of #ahaa4 
,this comet was visible from  ,march    
#bf1 #ahaa1 to ,august #ag1 #ahab1 a    
period of #eaj days4 ,it was one of  the
 most magnificent comets ever seen1 its 
tail being #ajj millions of  miles in   
length and its head #abg1jjj miles in   
diameter4 ,this wonderful  phenomenon   
was the subject of much investigation1  
particularly by  ,olbers1 the great     
,german astronomer4    ,heinrich        
,wilhelm ,matthias ,olbers was born at  
,arbergen1 a village near  ,bremen1     
,october #aa1 #ageh4 ,his father was a  
clergyman who1 in addition to           
considerable mathematical powers1 was an
 enthusiastic lover of  astronomy4 ,at  
the age of thirteen young ,olbers became

 deeply interested  in that science4    
,while taking an evening walk in the    
month of ,august1 he  observed the      
,pleiades1 and determined to find out to
 which constellation  they belonged4 ,he
 therefore bought some books on         
astronomy1 along with a  few charts of  
the sky1 and he began to study the      
science with much  enthusiasm4 ,he read 
every book he could lay his hands on1   
and a few  months sufficed to make him  
acquainted with all the constellations4 
,in #aggg1 when in his nineteenth year1 
,olbers entered the ,university of      
,gttingen to study medicine1 and at the 
same time he learned much  regarding    
mathematics and astronomy from the      
mathematician ,kaestner4  ,when         
twenty-one years of age he observed the 
stars at ,gttingen1 and  devised a      
method of calculating the orbits of     
comets1 the idea coming to  him while he
 was attending at the bedside of a      
fellow-student who had  taken ill4      
8,although not made public until #agig10

 writes ,miss ,clerke1  8#8,olbers'     
method' was then universally adopted1   
and is still regarded as  the most      
expeditious and convenient in cases     
where absolute rigour is  not required4 
,by its introduction1 not only many a   
toilsome and  thankless hour was spared1
 but workers were multiplied and        
encouraged in  the pursuit of labours   
more useful than attractive40           
,towards the end of #agha he returned to
 ,bremen1 settled as a medical  doctor1 
and continued in practice for about     
forty-one years4 ,but  although he had  
adopted perhaps the most toilsome       
profession1 his love  of science        
prevailed1 and night after night he     
explored the heavens with  untiring     
zeal4 ,he never slept more than four    
hours1 and the upper part  of his house 
in the ,sandgasse1 in ,bremen1 was      
fitted up with  astronomical            
instruments4 ,the largest telescope     
which he possessed was a  refractor #c  
inches in aperture4 ,he remained in     

active practice till  #ahbc1 when he    
retired1 and was enabled to devote more 
attention to his  beloved science4 ,he  
died on ,march #b1 #ahdj1 at the        
advanced age of  eighty-one4    ,miss   
,clerke says of ,olbers1 8,night after  
night1 during half a century  and       
upwards1 he discovered1 calculated1 or  
observed the cometary  visitants of     
northern skies40 ,he was the discoverer 
of the comet of  #ahae1 known as        
,olbers' comet4 ,it moves round the ,sun
 in a period of over  seventy years1 and
 returned to perihelion in #ahhg1       
forty-seven years  after the death of   
its discoverer4 ,the great comet of     
#ahaa was the  subject of a memoir which
 ,olbers published the following year1  
and in  which he originated the         
8electrical repulsion0 theory of comets'
 tails4  ,even after the fulfilment of  
,halley's great prediction1 comets were 
still looked upon with profound awe1 and
 the popular fear regarding them  was   
still prevalent4 ,olbers1 however1      

showed that the tails of comets         
resulted from purely natural causes4 ,he
 regarded the ,sun as possessed of  a   
repulsive as well as an attractive      
force1 and considered the tails to  be  
vapours repelled from the nucleus of the
 comet by the ,sun4 ,he  calculated that
 in the comet of #ahaa the particles of 
matter expelled  from the head reached  
the tail in eleven minutes1 with a      
velocity  comparable to that of light4  
,the theory of electrical repulsion1    
since  elaborated by other observers1 is
 now generally accepted among           
astronomers4 ,no other hypothesis       
represents in such a complete manner    
the formation and growth of the luminous
 appendages of the celestial  bodies so 
picturesquely called 8pale-winged       
messengers0 as that put  forward by the 
physician of ,bremen4    ,some years    
after ,olbers' famous theory was given  
to the world1 a great  advance was made 
in cometary astronomy by another great  
,german  astronomer1 his friend and     

pupil ,encke4 ,the son of a ,hamburg    
clergyman1  ,johann ,franz ,encke was   
born in that city in #agia1 and died in 
#ahfe at  ,spandau4 ,after taking part  
in the war against ,napoleon1 he was in 
#ahbb  appointed director of the ,gotha 
,observatory1 being called to ,berlin in
  #ahbe4 ,in early life he was the pupil
 of ,olbers and ,gauss1 and his         
investigations and discoveries formed an
 epoch in astronomy4 ,his most  famous  
discovery related to the little comet   
which bears his name4 ,the  comet was   
discovered by ,j4 ,l4 ,pons 7#agfa-ahca7
 at ,marseilles1 although  it had       
previously been seen by ,mchain and     
,caroline ,herschel4 ,in #ahai  ,encke  
computed the orbit of the comet1 and    
boldly announced that it  would reappear
 in #ahbb1 its period being about #c    
years1 or #abjh days4  ,in #ahbb the    
comet1 true to ,encke's prediction1     
returned to perihelion1  and was        
observed at ,paramatta in ,australia1   
the perihelion passage  taking place    

within three hours of the time predicted
 by ,encke4 ,as ,miss  ,clerke remarks1 
8,the importance of this event will be  
better understood  when it is remembered
 that it was only the second instance of
 the  recognised return of a comet2 and 
that it1 moreover1 established the      
existence of a new class of celestial   
bodies1 distinguished as comets of      
short period40    ,in #ahbe the comet   
was again observed by ,valz1 passing    
perihelion on  ,september #af1 and in   
#ahbh it was seen by ,struve4 ,encke now
 made a very  remarkable discovery4     
,determining its period with great      
accuracy1 in  #ahcb he found that his   
comet returned to perihelion two and a  
half hours  before the predicted time4  
,as this repeatedly happened1 ,encke put
  forward the theory that the           
acceleration was due to the existence of
 a  resisting medium in the             
neighbourhood of the ,sun1 too rarefied 
to retard  the planetary motions1 but   
quite dense enough to make the comet's  

path  smaller1 and to eventually        
precipitate it on the ,sun4 ,the theory 
was  widely accepted1 but after #ahfh   
the acceleration began to decrease1     
diminishing by one-half2 besides1 no    
other comet is thus accelerated1  and   
the hypothesis has accordingly been     
abandoned4    ,the second comet         
recognised as periodic was that         
discovered on ,february  #bg1 #ahbf1 by 
an ,austrian officer1 ,wilhelm von      
,biela 7#aghb-ahef71 and  ten days later
 by the ,french observer1 ,gambart      
7#ahjj-ahcf71 both of  whom1 in         
computing its orbit1 noticed a          
remarkable similarity to the  orbits of 
comets which appeared in #aggb and      
#ahje4 ,accordingly1 they  concluded it 
to be periodic1 with a period of between
 six and seven  years4 ,the comet       
returned in #ahcb4 ,in #ahbh ,olbers had
 published certain  calculations showing
 that portions of the comet would sweep 
over the  part of the ,earth's orbit a  
month later than the ,earth itself4     

,this gave  rise to a panic that the    
comet would destroy the ,earth1 which   
did not  subside till it was announced  
by ,arago that the ,earth and the comet 
would at no time approach to within     
fifty million miles of each other4  ,the
 comet returned again in the end of     
#ahde4 ,it was kept well in view by     
astronomers in ,europe and ,america4 ,on
 ,december #ai1 #ahdf1 ,hind noticed    
that the comet was pear-shaped1 and ten 
days later it had divided in  two4 ,the 
two comets returned again in #aheb and  
were well observed2 but  they were never
 seen again1 at least as comets4 ,their 
subsequent history  belongs to meteoric 
astronomy4    ,a comet discovered by    
,faye at ,paris in #ahdc was found to   
have a period  of seven and a half      
years4 ,it has returned regularly since 
its  discovery1 true to astronomical    
prediction4 ,its motion was particularly
  investigated for traces of a resisting
 medium1 by ,didrik ,magnus ,axel       
,mller 7#ahcj-ahif71 director of the    

,lund ,observatory1 who reached a       
negative conclusion4    ,in #ahce       
,halley's comet returned to perihelion1 
and was attentively  studied by the most
 famous astronomers of the age4 ,it was 
particularly  studied by ,sir ,john     
,herschel and by ,bessel1 who assisted  
in developing  ,olbers' theory of       
electrical repulsion4 ,but the most     
brilliant comet of  the century was that
 which suddenly appeared on ,february   
#bh1 #ahdc1 in  the vicinity of the     
,sun4 ,this great comet1 whose centre   
approached the  ,sun within #gh1jjj     
miles1 rushed past its perihelion at the
 speed of #cff  miles a second4 ,the    
comet's tail reached the length of #bjj 
millions of  miles4 ,the comet of #ahdc 
was however outshone1 not in brilliance 
but as  a celestial spectacle1 by the   
great comet discovered on ,june #b1     
#aheh1 by  ,giovanni ,battista ,donati  
7#ahbf-ahgc7 at ,florence1 and since    
known by  his name4 ,it became visible  
to the naked eye on ,august #ai1 and was

  telescopically observed until ,march  
#d1 #ahei4 ,there was abundance of      
time1 therefore1 to study the comet1    
which was exhaustively observed by  ,g4 
,p4 ,bond at ,harvard4 ,his observations
 convinced him that the light  from     
,donati's comet was merely reflected    
sunshine1 and this was  generally       
accepted4 ,another great comet appeared 
in #ahfa4 ,like that of  #ahdc1 its     
appearance was sudden1 being observed   
after sunset on ,june #cj1  #ahfa1 when1
 says ,miss ,clerke1 8a golden yellow   
planetary disc1 wrapt in  dense         
nebulosity1 shone out while the ,june   
twilight in these latitudes  was still  
in its first strength40 ,on the same    
evening the ,earth and the  ,moon passed
 through the tail of the great comet4   
,the vast majority of  people never knew
 that such a phenomenon had taken place1
 and even the  astronomers only noticed 
a singular phosphorescence in the sky--a
 proof  of the extreme tenuity of       
comets4    ,the first application of the

 spectroscope to the light of comets was
  made by ,donati in #ahfd4 ,the        
spectrum was found to consist of three  
bright bands1 but ,donati was unable to 
identify them4 ,however1 his            
observation gave the death-blow to the  
theory that comets shone by  reflected  
light alone1 for it implied the         
existence of glowing gas in  them4 ,on  
the appearance in #ahfh of the periodic 
comet discovered by  ,friedrich ,august 
,theodor ,winnecke 7#ahce-ahig71 the    
spectrum was  examined by ,huggins1 who 
identified the bright bands with the    
spectrum  of hydrocarbon4 ,this was     
confirmed in regard to ,coggia's comet  
of #ahgd  by ,huggins himself1 and also 
,brdikhine and ,vogel4 ,the hydrocarbon 
spectrum is characteristic of comets1   
and has been recognised in all  those   
spectroscopically studied4    ,the time 
had now come for a more complete theory 
of comets than that of  ,olbers4 ,the   
theory of electrical repulsion was      
developed in #ahga by  ,zllner1 whose   

principle of investigation is thus      
described by ,miss  ,clerke3 8,the      
efficacy of solar electrical repulsion  
relatively to solar  attraction grows as
 the size of the particle diminishes40  
,if the  particle is small enough1 it   
will obey the repulsive1 and not the    
attractive1 power of the ,sun4 ,zllner  
considered that the smallest  particles 
of comets obeyed the repulsive power1   
and thus formed the  tails of comets4   
,the development of a complete cometary 
theory is due1  however1 to the genius  
of a ,russian astronomer4 ,theodor      
,alexandrovitch  ,brdikhine1 born in    
#ahca at ,nicolaieff1 was employed at   
,moscow  ,observatory from #aheg to     
#ahij1 when he was promoted to the      
position of  director at ,pulkowa4 ,he  
resigned in #ahie1 and spent his last   
years in ,st  ,petersburg1 where he died
 on ,may #ad1 #aijd4 ,from the beginning
 of his  astronomical career he was     
devoted to the study of comets and their
  tails1 but it was the appearance of   

,coggia's comet in #ahgd which marked   
the commencement of his most important  
observations4 ,in that year1 on  making 
certain calculations regarding the      
hypothetical repulsive force  exerted by
 the ,sun on various comets1 he reached 
the conclusion that the  values         
representing the intensity of the       
repulsion fell into three  classes4     
,this was the first hint of a           
classification of cometary tails4       
,meanwhile he carefully studied the     
tails of comets both from direct        
observation and from drawings4    ,in   
#ahgg he wrote3 8,i suspect that comets 
are divisible into groups1 for  each of 
which the repulsive force is perhaps the
 same40 ,subsequent  investigations led 
,brdikhine to divide the tails of comets
 into three  types4 ,the first type     
consists of long1 straight tails1       
pointed directly  away from the ,sun1   
represented by the tails of the great   
comets of #ahaa1  #ahdc1 and #ahfa4 ,in 
the second type1 represented by         

,donati's and ,coggia's  comets1 the    
tails1 although pointed away from the   
,sun1 appear  considerably curved4 ,in  
the third type the tails are1 to quote  
,miss  ,clerke1 8short1 strongly-bent1  
brushlike emanations1 and in bright     
comets seem to be only found in         
combination with tails of the higher    
classes40    ,in #ahgi ,brdikhine fully 
developed his cometary theory4 ,assuming
 the  reality of the repulsive force1 he
 concluded that to produce tails of  the
 first type1 the repulsion requires to  
be twelve times greater than  the solar 
attraction2 the production of tails of  
the second type  necessitates a         
repulsive force about equal to gravity2 
while the force  producing third-type   
tails has only one-fourth the power of  
gravitation4  ,it was concluded that the
 tails are formed by particles of matter
  repelled from the comet by the        
repulsive force of the ,sun1 and in     
tails  of the first type the velocity   
with which these particles leave the    

body  of the comet is four or five miles
 a second4 ,brdikhine reached the       
conclusion that the ,sun's repulsive    
force is invariable1 and that the       
different types of tails are formed by  
the same force acting on  different     
elements4 ,the numbers #ab1 #a1 and 1   
are inversely proportional  to the      
atomic weights of hydrogen1 hydrocarbon 
gas1 and iron vapour4  ,here1 then1 was 
the key to the mystery4 ,brdikhine      
pointed out that in  all probability the
 first-type tails are formed of         
hydrogen1 the second  of hydrocarbon1   
and the third of iron1 with a mixture of
 sodium and  other elements4    ,within 
a few years of the publication of       
,brdikhine's theory1 five  bright comets
 made their appearance1 and there was   
abundant chance of  testing the theory  
spectroscopically4 ,in #ahhb ,well's    
comet was  particularly studied at      
,greenwich by ,maunder1 who discerned a 
sodium-line in its spectrum4 ,the       
magnificent comet which appeared in     

#ahhb was spectroscopically studied at  
,dunecht in ,aberdeenshire by ,ralph    
,copeland 7#ahcg-aije71                 
,astronomer-,royal of ,scotland1 who    
identified in  its spectrum the         
prominent iron-lines as well as the     
sodium-line4 ,these  observations were  
certainly confirmatory of ,brdikhine's  
theory4 ,it  should also be stated1     
however1 that several comets have shown1
 in  addition to the hydrocarbon        
spectrum1 that of reflected sunlight1   
which  proves that the light we receive 
from comets is of a compound nature4    
,the comet which appeared in #ahhj was  
announced by ,benjamin ,apthorp  ,gould 
7#ahbd-ahif7 to be a return of the great
 comet of #ahdc4  ,calculations by      
,gould1 ,copeland1 and ,hind revealed a 
close similarity  between the elements  
of the two orbits4 ,eventually it had to
 be admitted  that the comets were      
separate bodies travelling in the same  
orbit4 ,then1  two years later1 the     
great ,september comet of #ahhb was     

found to revolve  in the same orbit as  
those of #affh1 #ahdc1 and #ahhj4 ,four 
years later1  another comet1 discovered 
in #ahhg1 was found to move in the same 
path4    ,closely allied to this subject
 is the existence of 8comet families10  
demonstrated by ,hoek of ,utrecht in    
#ahfe1 and mentioned in our chapter on  
the ,outer ,planets4 ,these comets are  
found to be dependent on the  planets1  
,jupiter1 ,saturn1 ,uranus1 and         
,neptune1 each possessing a             
comet-group4 ,various theories have been
 advanced to account for the  existence 
of these groups4 ,one of these theories 
is that the comets have  been captured  
by the various planets1 who have forced 
them into their  present orbits4 ,a     
mathematical study by ,jean ,pierre     
,octave ,callandrean  7#aheb-aijd7 shows
 that the large number of comets        
possessed by the  various planets may be
 explained by the disintegration of     
large comets  into small ones4 ,the     
capture theory1 it must be remembered1  

is purely  hypothetical1 and must not be
 regarded as anything but a theory4 ,all
  that we really know is the existence  
of comet-families1 and of comets  moving
 in the same orbits4    ,the first      
photograph of a comet was that of       
,donati's1 taken in #aheh by  ,bond4 ,in
 #ahha ,tebbutt's comet was photographed
 in ,england by ,huggins1  and in       
,america by ,henry ,draper 7#ahcg-ahhb71
 while in #ahhb ,gill secured  excellent
 photographs of the great ,september    
comet4 ,the first  photographic         
discovery of a comet was made by        
,barnard in #ahib4 ,since  then         
photography has been much used in       
cometary astronomy4 ,no bright  comets  
have appeared since #ahhb1--;if we      
except the comet of #aija1 only  seen in
 the southern hemisphere1--although     
several have been just visible  to the  
naked eye1 among them ,swift's comet of 
#ahib and ,perrine's in the  autumn of  
#aijb4 ,telescopic comets1 however1 are 
very numerous1 and a  year never passes 

without one or more being discovered4   
,the ordinary  periodic comets1 such as 
,encke's1 ,faye's1 and others1 are very 
faint1  and are becoming fainter at each
 return--a clear proof that comets die1 
as ,kepler said three centuries ago4    
,this brings us to the subject of the   
next chapter1 ,meteoric ,astronomy4     
,,chapter ,,viii4                       
,,meteors4      ,there is no more       
interesting chapter in the history of   
astronomy than  that relating to        
meteors4 ,a hundred years ago           
shooting-stars were not  considered to  
be astronomical phenomena4 ,they were   
supposed to be merely  inflammable      
vapours which caught fire in the upper  
regions of our  atmosphere1 although    
both ,halley and the scientist ,ernst   
,chladni  7#agef-ahbg7 had notions of   
their celestial origin4 ,for            
thirty-three  years after the beginning 
of the century1 however1 nothing was    
heard of  meteoric astronomy1 nor was   
the subject considered as part of the   

astronomer's labours4    ,a great       
meteoric shower took place on the night 
of ,november #ab and  morning of        
,november #ac1 #ahcc4 ,the shower was   
probably the grandest ever  witnessed1  
the shooting-stars being literally      
innumerable4 ,the display  was best     
observed in ,america1 and was           
attentively watched by ,denison         
,olmsted 7#agia-ahei71 ,professor of    
,mathematics at ,yale1 and by the       
,american physicist1 ,a4 ,c4 ,twining   
7#ahja-ahhd74 ,these investigators      
discovered that all the meteors which   
fell during the great shower  seemed to 
come from the same part of the celestial
 vault4 ,in other  words1 their paths1  
when traced back1 were found to converge
 to a point  near the star  ,leonis4    
,this observation gave the death-blow to
 the  theory of their terrestrial       
origin4 ,the point known as the         
8radiant0 was  clearly a point          
independent of the ,earth4 ,olmsted also
 recognised the  fact that the shower   

had taken place in the previous year1   
and he  regarded it as produced by a    
swarm of particles moving round the ,sun
 in  a period of #ahb days4 ,soon after 
this it was noticed that the phenomenon 
took place in #ahcd and subsequent years
 with gradually decreasing  intensity4  
,it was then remembered that ,humboldt  
had observed in ,november  #agii a very 
brilliant shower1 and accordingly       
,olbers suggested that  another shower  
might be seen in #ahfg4    ,the falling 
stars of ,august were next proved by    
,adolphe ,quetelet  7#agia-ahgd7 to form
 another meteoric system2 and           
accordingly the theory  of ,olmsted that
 the ,november meteors moved round the  
,sun in #ahb days had  to be abandoned1 
for1 says ,miss ,clerke1 8,if it would  
be a violation of  probability to       
attribute to one such agglomeration a   
period of an  exact year or sub-multiple
 of a year1 it would be plainly absurd  
to  suppose the movements of two or more
 regulated by such highly  artificial   

conditions40 ,accordingly ,erman        
suggested in #ahci the theory  that     
meteors revolved in closed rings1       
intersecting the terrestrial  orbit2 and
 that when the ,earth crossed through   
the point of  intersection1 it met some 
members of the swarm4 ,the subject now  
remained  in abeyance for thirty-four   
years1 if we except some wonderful ideas
 put  forward in #ahfa by ,daniel       
,kirkwood 7#ahac-ahif71 an ,american    
astronomer1 who stated his belief in the
 disintegration of comets into  meteors2
 but little attention was paid to his   
opinions4 ,in #ahfd the  subject was    
taken up by ,hubert ,anson ,newton      
7#ahcj-ahif71 ,professor at  ,yale1 who 
undertook a search through ancient      
records for the  thirty-three-year      
period of the ,leonids or ,november     
meteors4 ,his search  was highly        
successful1 and having demonstrated the 
existence of the  period1 ,newton set   
himself to determine the orbit4 ,he     
indicated five  possible orbits for the 

swarm1 ranging from #cc years to #ced   
days4  ,newton was unable to solve the  
question mathematically2 but here       
,adams1  the discoverer of ,neptune1    
came to the rescue1 and demonstrated    
that the  period of #cc years was alone 
possible1 and that the others were      
untenable4 ,these investigations1       
completed in ,march #ahfg1 proved the   
existence of a great meteoric orbit     
extending to the orbit of ,uranus4      
,meanwhile ,newton had predicted a      
meteoric shower on the evening of       
,november #ac and morning of ,november  
#ad1 #ahff4 ,his prediction was         
fulfilled4 ,the shower was inferior to  
that of #ahcc1 but was still a          
magnificent spectacle4 ,sir ,robert     
,ball1 then employed at ,lord ,rosse's  
,observatory1 observed the shower1 and  
records the impossibility of  counting  
the meteors4 ,this great shower         
attracted the attention of  astronomers 
all over the world to the study of      
meteors4 ,meanwhile  ,schiaparelli had  

been working at the subject for some    
time1 and in four  letters addressed to 
,secchi1 towards the end of #ahff1 he   
showed that  meteors were members of the
 ,solar ,system1 possessed of a greater 
velocity than that of the ,earth1 and   
travelling in orbits resembling  those  
of comets1 in the fact that they moved  
in no particular plane1 and  that their 
motion was both direct and retrograde4  
,schiaparelli computed  the orbit of the
 ,perseids or ,august meteors1 and was  
astonished to find  it identical with   
the comet of ,august #ahfb4 ,this was a 
proof of the  connection between these  
two apparently widely different types of
  celestial bodies4 ,early in #ahfg     
,schiaparelli found that ,le ,verrier's 
elements for the orbit of the ,leonids  
were identical with those of the  comet 
of #ahff1 discovered by ,ernst ,tempel  
7#ahba-ahhi74 ,peters of  ,altona had   
meanwhile reached the same conclusion2  
while ,edmund ,weiss  7born #ahcg7 of   
,vienna pointed out the similarity of   

the orbit of a  star-shower on ,april   
#bj and that of the comet of #ahfa4 ,he 
also drew  attention1 independently of  
,galle and ,d',arrest1 to the close     
connection  between the orbits of the   
lost ,biela's comet and the ,andromedid 
meteors  of ,november4    ,all doubt as 
to the connection of comets and meteors 
was removed by the  great shower on     
,november #bg1 #ahgb4 ,biela's lost     
comet was due at  perihelion in #ahgb1  
and although searched for was not       
observed2 but when  the ,earth crossed  
its orbit1 a great meteoric shower took 
place4 8,it  became evident10 says ,miss
 ,clerke1 8that ,biela's comet was      
shedding over  us the pulverised        
products of its disintegration40 ,the   
shower was little  inferior to that of  
#ahff4 ,meanwhile ,ernst ,klinkerfues   
7#ahbg-ahhd71  ,professor at ,gttingen1 
believing that ,biela's comet itself had
  encountered the ,earth1 telegraphed to
 ,norman ,robert ,pogson  7#ahbi-ahia71 
,government astronomer at ,madras1 to   

search for the comet in  the opposite   
region of the sky4 ,pogson did observe a
 comet1 but  certainly not ,biela's1    
although probably another fragment of   
the missing  body4    ,the theory of the
 actual disintegration of comets was    
enunciated by  ,schiaparelli in #ahgc1  
and developed in his work #8,le ,stelle 
,cadenti4' ,he  was led to regard comets
 as cosmical clouds formed in space by  
8the  local concentration of celestial  
matter40 ,he then remarks that a        
cosmical cloud seldom penetrates to the 
interior of the ,solar ,system1  8unless
 it has been transformed into a         
parabolic current10 which may  occupy   
years1 or centuries1 in passing its     
perihelion1 8forming in space  a river1 
whose transverse dimensions are very    
small with respect to its  length3 of   
such currents1 those which are          
encountered by the earth in  its annual 
motion are rendered visible to us under 
the form of showers  of meteors         
diverging from a certain radiant40      

,schiaparelli next pointed out that when
 the current of meteors  encounters a   
planet1 the resulting perturbations     
cause some of the  meteoric bodies to   
move in separate orbits1 forming the    
bolides and  aerolites which fall from  
the sky at intervals4 8,the term falling
  stars0 he says1 8expresses simply and 
precisely the truth respecting  them4   
,these bodies have the same relation to 
comets that the small  planets between  
,mars and ,jupiter have to the larger   
planets40 ,in the  third chapter of his 
#8,le ,stelle ,cadenti' he explicitly   
states that 8the  meteoric currents are 
the products of the dissolution of      
comets1 and  consist of minute particles
 which certain comets have abandoned    
along  their orbits1 by reason of the   
disintegrating force which the ,sun and 
planets exert on the rare materials of  
which they are composed40    ,in #ahgh  
,alexander ,stewart ,herschel 7born     
#ahcf71 son of ,sir ,john  ,herschel1   
and a famous meteoric observer1         

published a list of known or  suspected 
coincidences of meteoric and cometary   
orbits1 amounting to  seventy-six4      
,meanwhile much progress has since been 
made in the  observation of meteoric    
showers and the determination of their  
radiant  points4 ,in this branch of     
astronomy1 by far the greatest name is  
that of  ,william ,frederick ,denning1  
the self-made ,english astronomer4 ,born
 at  ,redpost1 in ,somerset1 in #ahdh1  
his career of meteoric observation      
commenced in #ahff4 ,for the past forty 
years he has attentively devoted        
himself to the observation of meteors4  
,from #ahgb to #aijc he determined  the 
radiant points of no fewer than #aagi   
meteoric showers4 ,in addition  to this1
 he published1 in #ahii1 a catalogue of 
meteoric radiants1  containing #dcfg2   
and he has carefully studied the        
remarkable objects  known as fireballs  
or 8sporadic meteors40 ,he has          
occasionally been able  to trace a      
connection between fireballs and weak   

meteoric showers1 but  he concludes that
 they 8must either be merely single     
sporadic bodies1 or  else the survivors 
of some meteor group1 nearly exhausted  
by the waste  of its material during    
many past ages40 ,all of ,denning's     
meteoric work  has been done in his     
spare time1 for it must be borne in mind
 that he  pursues the profession of     
accountant in ,bristol1 and that only   
his  leisure hours have been devoted to 
the science of astronomy4 ,his          
researches have been entirely conducted 
with the unaided eye4 ,his only         
instrument is a perfectly straight wand1
 which he uses as a help and  corrective
 to the eye in ascribing the paths of   
the meteors4 ,thanks to  the laborious  
work of this able ,english astronomer1  
the observation of  meteors is now a    
scientific branch of astronomy4 ,in the 
words of  ,maunder1 8for six thousand   
years men stared at meteors and learned 
nothing1 for sixty years they have      
studied them and learned much1 and  half

 of what we know has been taught us in  
half that time by the efforts  of a     
single observer40    ,further meteoric  
showers from ,biela's comet were seen in
 #ahhe and #ahib4  ,the ,leonid shower  
was confidently predicted for #ahii1 in 
accordance with  the thirty-three-year  
period1 but the great display did not   
come off1  either in #ahii or #aijj4 ,in
 #aija there was a certain weak shower  
observed  in ,america2 and similar      
displays took place in #aijc and #aijd4 
,many  explanations have been given as  
to the failure of the shower1 the most  
probable idea being that the attraction 
of ,jupiter diverted the meteors  from  
their course4    ,denning's observations
 on meteors resulted1 as early as #ahgg1
 in the  discovery of so-called         
8stationary radiants40 ,the             
radiant-point of a  long enduring shower
 usually exhibits an apparent motion1   
resulting from  the combined orbital    
motions of the ,earth and the meteors2  
but ,denning  found that in some cases  

the shower1 though lasting for months1  
persistently exhibited the same         
radiant-point1 implying that the motion 
of the ,earth must be insignificant     
compared with that of the meteors1      
computed by ,ranyard at #hhj miles per  
second4 ,the difficulty of admitting  so
 great a velocity led the ,french       
astronomer1 ,franois ,felix  ,tisserand 
7#ahde-ahif71 to doubt the existence of 
these stationary  radiants2 but the fact
 of their existence cannot be doubted1  
although no  really satisfactory        
explanation has been offered4           
,another type of meteors comprises the  
bodies termed respectively as  bolides1 
uranoliths1 and aerolites1--stones which
 fall to the ,earth from  the sky4 ,in  
#ahjj the ,french ,academy declared the 
accounts of stones  having fallen from  
the heavens to be absolutely untrue4    
,three years  later an aerolite fell at 
,laigle1 in the ,department of ,orne1 on
 ,april  #bf1 #ahjc1 attended by a      
terrific explosion4 ,in the words of    

,flammarion1  8,numerous witnesses      
affirmed that some minutes after the    
appearance of a  great bolide1 moving   
from south-east to north-east1 and which
 had been  perceived at ,alenon1 ,caen1 
and ,falaise1 a fearful explosion1      
followed  by detonations like the report
 of cannon and the fire of musketry1    
proceeded from an isolated black cloud  
in a very clear sky4 ,a great  number of
 meteoric stones were then precipitated 
on the surface of the  ground1 where    
they were collected1 still smoking1 over
 an extent of  country which measured no
 less than seven miles in length40      
,some aerolites1 instead of being       
shattered into fragments1 have been     
observed to fall to the ,earth intact1  
and bury themselves in the ground4      
,numerous instances have been observed  
during the last century1 and  masses of 
meteoric stones have been found in      
positions which clearly  indicate that  
they must have fallen from the sky4     
,chemists have made  analyses of the    

elements in these remarkable bodies1 and
 have found them  to contain iron1      
magnesium1 silicon1 oxygen1 nickel1     
cobalt1 tin1  copper1 c4 ,the spectrum  
of these aerolites1 raised to           
incandescence1  has been studied by     
,vogel and by the ,swedish observer1    
,bernhardt  ,hasselberg 7born #ahdh71   
who detected the presence of            
hydrocarbons1  which are also present in
 cometary spectra4    ,when the         
existence of aerolites as celestial     
bodies was first  recognised1 ,laplace  
suggested that they had been ejected    
from volcanoes  on the ,moon4 ,this     
theory1 although supported by ,olbers   
and other  astronomers1 was soon        
rejected4 ,next1 it was suggested that  
they were  ejected from the ,sun1 and   
,proctor believed them to come from the 
giant  planets4 ,a very detailed        
discussion of the subject is to be found
 in  ,ball's #8,story of the ,heavens'  
7#ahhf71 in which he expresses views in 
harmony with those of the ,austrian     

physicist ,tschermak4 ,ball             
demonstrated that the meteors which fall
 to the ,earth cannot have come  from   
any other planet1 nor from the ,sun4    
,accordingly1 he concluded that  they   
were originally ejected by the volcanoes
 of the ,earth many ages  ago1 when they
 were active enough to throw up pieces  
of matter with a  velocity great enough 
to carry them away from the ,earth      
altogether4 ,such  meteors would1       
however1 intersect the terrestrial orbit
 at each  revolution4    ,the           
alternative theory to this1 supported by
 ,schiaparelli and ,lockyer1  is that   
the aerolites are merely larger members 
of the meteor-swarms1  which have been  
deflected from their paths4 ,the chief  
objection to this  theory is the absence
 of connection between the meteoric     
showers and the  falls of aerolites and 
bolides4 ,only on one occasion was a    
meteoric  stone observed to fall during 
a shower4 ,on ,november #bg1 #ahhe1     
during the  shower of ,andromedid       

meteors from ,biela's comet1 a large    
bolide1  weighing more than eight       
pounds1 fell at ,mazapil1 in ,mexico4   
,this1  however1 was the only case      
hitherto observed2 and it may have been 
merely a coincidence4                   
,,chapter ,,ix4                         
,,the ,,stars4      ,the most remarkable
 progress in astronomy during the past  
century has  been in the department of  
sidereal science1 or the study of the   
,suns of  space1 observed for their own 
sakes1 and not merely for the purpose of
  determining the positions of the ,sun 
and ,moon1 and to assist navigation4    
,thanks to ,herschel1 the nineteenth    
century witnessed the steady            
development of stellar astronomy1       
combined with many important            
discoveries and investigations4    ,the 
one pre-,herschelian problem in sidereal
 astronomy was the distance  of the     
stars4 ,owing to its bearing on the     
,copernican theory1 the problem  was    
attacked by the astronomers of the      

seventeenth and eighteenth  centuries4  
,herschel made numerous attempts to     
detect the parallax of the  brighter    
stars1 but failed4 ,meanwhile there had 
been many illusions4  ,piazzi believed  
that his instruments--which in reality  
were worn out and  unfit for use--had   
revealed parallaxes in ,sirius1         
,aldebaran1 ,procyon1 and  ,vega2       
,calandrelli1 another ,italian1 and     
,john ,brinkley 7#agfc-ahce71           
,astronomer-,royal of ,ireland1 were    
similarly deluded2 and in #ahba it was  
shown by ,friedrich ,georg ,wilhelm     
,struve 7#agic-ahfd71 the great ,german 
astronomer1 that no instruments then in 
use could possibly be successful  in    
measuring the stellar parallax4 ,a few  
years later1 however1  ,fraunhofer      
brought the refractor to a degree of    
perfection surpassing  all previous     
efforts4 ,in #ahbi he mounted for the   
observatory at  ,knigsberg a heliometer1
 the object-glass of which was divided  
in two1  and capable of very accurate   

measurements4 ,this heliometer          
eventually  revealed the parallax of the
 stars in the able hands of ,friedrich  
,wilhelm ,bessel4    ,friedrich ,wilhelm
 ,bessel was born at ,minden1 on the    
,weser1 south-west of  ,hanover1 on     
,july #bb1 #aghd4 ,his father was an    
obscure ,government  official1 unable to
 provide a university education for his 
son4 ,bessel's  love of figures1        
together with an aversion to ,latin1 led
 him to pursue a  commercial career4 ,at
 the age of fourteen1 therefore1 he     
entered as an  apprenticed clerk the    
business of ,kuhlenkamp  ,sons1 in      
,bremen4 ,he was  not content1 however1 
to remain in that humble position4 ,his 
great  ambition was to become supercargo
 on one of the trading expeditions sent 
to ,china2 and so he learned ,english1  
,spanish1 and geography4 ,but he  never 
became a supercargo4 ,in order to be    
fully equipped for such a  position1 he 
determined to learn how to take         
observations at sea1 and  his           

acquaintance with observation aroused a 
desire to study astronomy4  ,he         
constructed for himself a sextant1 and  
by means of this1 along with a  common  
clock1 he determined the longitude of   
,bremen4    ,such enthusiasm could not  
be long without its reward4 ,for several
 years  ,bessel remained a clerk1 and   
the hours devoted to study were those   
spared from sleep4 ,he studied the works
 of ,bode1 ,von ,zach1 ,lalande1 and    
,laplace1 and in two years was able to  
compute the orbits of comets by  means  
of mathematics4 ,from some observations 
of ,halley's comet at its  appearance in
 #afjg1 ,bessel calculated its orbit1   
and forwarded the  calculation to       
,olbers1 then the greatest authority on 
cometary  astronomy4 ,olbers was        
delighted at this work1 and he sent the 
results to  ,von ,zach1 who published   
them4 ,the self-taught young astronomer 
had  accomplished a piece of work which 
fifteen years before had taxed the      
skill and patience of the ,french       

,academy of ,sciences4    ,in #ahje1    
,harding1 ,schrter's assistant at       
,lilienthal1 resigned his  position for 
a more promising one at ,gttingen4      
,olbers procured for  ,bessel the offer 
of the vacant post1 which the latter    
accepted4 ,at  ,lilienthal ,bessel      
received his training as a practical    
astronomer4 ,he  remained in ,schrter's 
observatory until #ahji4 ,although only 
twenty-five  years of age1 he had become
 so well known in ,germany that in that 
year  he was appointed ,professor of    
,astronomy in the ,university of        
,knigsberg1  and was chosen to          
superintend the erection of the new     
observatory there4  ,within a few years 
a clerk in a commercial office had      
worked his way  from obscurity to fame4 
,in #ahac the ,knigsberg ,observatory   
was completed1 and here ,bessel worked  
for thirty-three years1 until his death1
 on ,march #ag1 #ahdf4 ,it was only     
about ten years before his death that he
 commenced his search for the  stellar  

parallax1 with the aid of ,fraunhofer's 
magnificent heliometer4  ,he determined 
to make a series of measures on a small 
double star of the  fifth magnitude in  
the constellation ,cygnus1 named #fa    
,cygni1 the large  proper motion of     
which led him to suspect its proximity  
to the ,solar  ,system4 ,from ,august   
#ahcg to ,september #ahch he made       
observations on #fa  ,cygni1 and he     
found that there was an annual          
displacement which could  only be       
attributed to parallax4 ,in order to    
have no mistake1 he made  another year's
 observations1 which confirmed the      
results he arrived at  previously1 and  
all doubt was removed by a third series4
 ,the resulting  parallax was #jcdhc1   
corresponding to a distance of #fjj1jjj 
times the  ,earth's distance from the   
,sun4 ,this was confirmed some years    
later by ,c4  ,a4 ,f4 ,peters at        
,pulkowa1 and still later by ,otto      
,struve1 who estimated  the distance at 
forty billions of miles4 ,meanwhile1 ,f4

 ,g4 ,w4 ,struve1  working at ,pulkowa1 
found a parallax of #jbfac for ,vega1   
but this was  afterwards found to be    
considerably in error4 ,accordingly1    
,struve does  not rank with ,bessel as a
 successful measurer of star-distance4  
,but  independently of ,bessel1 another 
accurate measure had been made by       
,thomas ,henderson1 the great ,scottish 
astronomer4    ,born in ,dundee in      
#agih1 ,thomas ,henderson was the       
youngest of five  children of a         
hard-working tradesman4 ,after education
 in his native town  he went to         
,edinburgh1 where he worked for years as
 an advocate's clerk1  pursuing studies 
in astronomy as a recreation from his   
boyhood4 ,in #ahca  he had become so    
well known1 that he received the        
appointment of  ,astronomer-,royal at   
the new observatory at the ,cape of     
,good ,hope4 ,but  the climate of ,south
 ,africa did not suit his health1 and   
after a year he  returned to ,scotland4 
,in #ahcd he became ,professor of       

,astronomy in the  ,university of       
,edinburgh1 and ,astronomer-,royal of   
,scotland1 which  position he held till 
his death on ,november #bc1 #ahdd1 at   
the early age  of forty-six4    ,during 
a year's work at the ,cape1 ,henderson  
undertook a series of  observations on  
the bright southern star1  ,centauri1   
with a view to  determining its         
parallax4 ,these observations were made 
in #ahcb and #ahcc1  but were not       
reduced until ,henderson's return to    
,scotland4 ,at length1 on  ,january #c1 
#ahci1 he announced to the ,royal       
,astronomical ,society that he  had     
succeeded in measuring the parallax of  
,centauri1 which he  determined as about
 one second of arc1 corresponding to a  
distance of  about twenty billions of   
miles4 ,this result was confirmed by the
  observations of ,thomas ,maclear      
7#agid-ahgi71 his successor at the      
,cape1  and by those of later observers1
 notably ,sir ,david ,gill1 who has     
reduced  the parallax to #jge4    ,other

 determinations of stellar parallax1    
some genuine and others  illusory1 were 
made soon after these successful        
observations4 ,c4 ,a4 ,f4  ,peters and  
,otto ,struve at ,pulkowa were among the
 most famous  parallax-hunters in the   
middle of the century4 ,one of the most 
successful searchers after parallax was 
the ,german astronomer ,friedrich       
,brnnow 7#ahba-ahia71 who was employed  
from #ahfe to #ahgd as                  
,astronomer-,royal of ,ireland4 ,he     
determined the parallax of ,vega as     
#jac1 and this was confirmed in #ahhf by
 ,hall at ,washington3 while he         
measured the parallax of the star       
,groombridge #ahcj1 which turned out to 
be #jji4 ,he resigned his post in #ahgd1
 and his successor at ,dublin           
,observatory proved to be his successor 
also in this branch of astronomy4       
,robert ,stawell ,ball1 born in ,dublin 
in #ahdj1 was astronomer to ,lord       
,rosse in #ahfe and #ahff1 and became in
 #ahgd ,astronomer-,royal of ,ireland   

in succession to ,brnnow1 a position    
which he filled until his  appointment  
in #ahib as ,professor of ,astronomy at 
,cambridge1 and director  of the        
observatory there4 ,during his term of  
office in ,dublin he  undertook1 in     
#ahha1 a 8sweeping search0 for large    
parallaxes1 thereby  disproving certain 
ideas as to the proximity to the ,earth 
of red and  temporary stars2 while he   
also determined the parallax of the star
 #afah  ,groombridge4    ,but the       
greatest extension of our knowledge of  
stellar distances1 in  recent years1 is 
due to a ,scottish astronomer1 who has  
maintained the  reputation of ,scotland1
 and also of the ,cape ,observatory1 in 
this line  of research4 ,born in        
,aberdeen in #ahdc1 ,david ,gill        
directed ,lord  ,lindsay's private      
observatory at ,dunecht1 in             
,aberdeenshire1 from #ahgf to  #ahgi4   
,in the latter year he succeeded ,edward
 ,james ,stone 7#ahca-ahig7  as         
,astronomer-,royal at the ,cape1 a      

position which he has since filled  with
 conspicuous ability4 ,from #ahha he has
 been engaged in the hunt for  parallax4
 ,in conjunction with ,william ,lewis   
,elkin 7born #ahee71 now  director of   
,yale ,college ,observatory1 he         
determined the parallaxes of  nine stars
 with the aid of ,lord ,lindsay's       
heliometer4 ,in #ahhg1 with a  larger   
instrument1 he resumed the search1 while
 ,elkin worked in  co-operation with    
him1 but at ,yale ,observatory1 where he
 undertook the  measurement of the      
parallaxes of northern stars4 ,he fixed 
in #ahhh an  average parallax for       
first-magnitude stars1 which was        
determined at  #jjhi1 corresponding to a
 journey for light of thirty-six years4 
,most of the successful determinations  
of parallax have been made by the       
8relative0 method--that is1 the         
determination of the displacement of a  
star in reference to another star1      
assumed to be situated at an            
immeasurable distance4 ,the method of   

absolute parallax1 on the other         
hand1--the star's displacement in right 
ascension and declination1--has  been   
seldom used1 owing to the laborious     
reduction which has to be gone  through 
before the result can be reached4 ,in   
#ahhe1 however1 a series of             
observations were undertaken at ,leyden 
by ,jacobus ,cornelius ,kapteyn  7born  
#ahea71 who determined by the absolute  
method the parallaxes of  fifteen       
northern stars4    ,the first           
application of photography to the       
problem was due to the zeal  and energy 
of ,charles ,pritchard 7#ahjh-ahic71    
,professor of ,astronomy at  ,oxford1   
who determined by this method the       
parallax of #fa ,cygni1 which he        
announced in #ahhf to be #jdch1 in      
agreement with ,ball's determination4   
,he also determined the average parallax
 of second-magnitude stars1 which  came 
out as #jjef4 ,since the time of        
,pritchard's observations various  other
 more or less satisfactory              

determinations of parallax have been    
made4 ,few of the parallax              
determinations are probably very        
accurate1 and  none exact2 but an idea  
of the difficulty of the measurement may
 be  gathered from the remark of an     
,american writer1 ,mr ,g4 ,p4 ,serviss1 
that  the displacement 8is about equal  
to the apparent distance between the    
heads of two pins1 placed an inch apart1
 and viewed from a distance of a        
hundred and eighty miles40    ,closely  
allied to the question of parallax is   
the determination of the  exact         
positions of the stars and the formation
 of star-catalogues4 ,in  this branch1  
too1 much is due to the genius of       
,bessel4 ,the observations  of ,bradley 
at ,greenwich from #agej to #agfb were  
reduced by ,bessel into  the form of a  
catalogue1 which was published in #ahah1
 with the title of  #8,fundamenta       
,astronomi4' ,during the years #ahba to 
#ahbc ,bessel took  #ge1jaa             
observations1 by which he brought up the

 number of accurately  known stars to   
#ej1jjj4 ,at the same time notable      
catalogues had been  constructed1       
particularly by the ,english astronomer1
 ,francis ,baily  7#aggd-ahdd71 and by  
,giovanni ,santini 7#aghf-ahgg71        
director of the  observatory at ,padua2 
but ,bessel's successor in this branch  
of research  was ,friedrich ,wilhelm    
,august ,argelander 7#agii-ahge74 ,in   
#ahba he became  assistant to ,bessel at
 ,knigsberg1 in #ahbc director of the   
,observatory  at ,abo1 in ,finland1 and 
in #ahcg of that at ,bonn4 ,here he     
commenced in  #aheb the great #8,bonn   
,durchmusterung1' a catalogue and atlas 
of #cbd1aih  stars visible in the       
northern hemisphere4 ,the great         
catalogue was  published in #ahfc4      
,after ,argelander's death it was       
extended so as to  include #acc1fei     
stars in the southern hemisphere1 by his
 assistant  ,eduard ,schnfeld           
7#ahbh-ahia71 who succeeded him in #ahge
 as director of  ,bonn ,observatory1    

where he died in #ahia4 ,meanwhile a    
greater undertaking  was commenced in   
#ahfe by the ,astronomische             
,gesellschaft4 ,this was the            
co-operation of thirteen observatories  
in ,europe and ,america for the  exact  
determination of the places of #ajj1jjj 
of ,argelander's stars4    ,in the      
southern hemisphere1 working at ,cordova
 in ,argentina1 was the  great ,american
 astronomer1 ,gould1 whose              
#8,uranometria ,argentina1'  published  
in #ahgi1 gives the magnitudes of #haih 
stars1 and whose  ,argentine ,general   
,catalogue1 containing reference of     
#cb1ddh stars1 was  published in #ahhf4 
,the late ,radcliffe observer1 ,stone1  
published a  useful catalogue in #ahhj  
from his observations at the ,cape4     
,the application of photography to the  
work of star-charting dates from  #ahhb1
 when ,gill photographed the comet of   
#ahhb1 and was struck with the          
distinctness of the stars on the        
background4 ,for some time he had       

contemplated the extension of the       
#8,durchmusterung1' from the point where
  ,schnfeld left it1 to the southern    
pole1 and the idea struck him to        
utilise photography for the purpose4 ,in
 #ahhe1 accordingly1 ,gill  commenced   
work1 and in four years all the         
photographs were taken4 ,the  reduction 
of the observations into the form of a  
catalogue was  spontaneously undertaken 
by the great ,dutch astronomer1         
,kapteyn1 who was  occupied with the    
work for fourteen years1 until in #aijj 
the great  catalogue1 known as the      
#8,cape ,photographic ,durchmusterung1' 
was  completed4 ,half a million stars   
are represented on the plates taken at  
the ,cape4    ,by the time the          
#8,durchmusterung' was completed1 a     
greater undertaking  was in progress4   
,paul and ,prosper ,henry1 astronomers  
at the ,paris  ,observatory1 when       
engaged in continuing ,chacornac's      
ecliptic charts1  applied photography to
 their work1 and found it very          

successful4  ,accordingly ,gill's       
proposal1 on ,june #d1 #ahhf1 of an     
,international  ,congress of            
,astronomers1 to undertake a            
photographic survey of the  heavens1 was
 enthusiastically received by the       
,french astronomers4 ,the  ,congress met
 at ,paris in #ahhg1 under the          
presidentship of ,amde  ,mouchez        
7#ahba-ahib71 director of the ,paris    
,observatory1 fifty-six  astronomers of 
all nations being present4 ,the         
,congress resolved to  construct a      
,photographic ,chart1 and a ,catalogue1 
the former containing  twenty million   
stars1 the latter a million and a       
quarter4 ,meetings were  held in ,paris 
in #ahia1 #ahic1 #ahif1 and #aijj to    
superintend the progress  of the work1  
which is now 7#aijf7 well advanced      
towards completion4    ,a unique star   
catalogue is in course of preparation by
 the ,scottish  astronomer1 ,william    
,peck 7born #ahfb71 astronomer to the   
,city of  ,edinburgh since #ahhi4 ,mr   

,peck's catalogue is accompanied by a   
series of  charts4 ,his star-magnitudes 
are those of all famous catalogues      
reduced  to a standard scale4 ,this     
catalogue1 the result of more than      
fifteen  years' work1 will be an        
important addition to the many valuable 
works of  the kind already in existence1
 and will further increase the already  
great reputation of ,scotsmen in        
practical astronomy4    ,the            
determination of the proper motions of  
the stars is another  important branch  
of practical astronomy in which much    
progress has been  made since the time  
of ,herschel4 ,stars with much larger   
proper motions  than those of the first 
magnitude have been discovered4 ,for    
many years  the small sixth-magnitude   
star in ,ursa ,major1 #ahcj             
,groombridge1 was  supposed to be the   
swiftest of the stars1 and was named by 
,newcomb the  8runaway star40 ,but in   
#ahig1 on examining the plates of the   
#8,cape  ,durchmusterung1' ,kapteyn     

discovered a still swifter star of the  
eighth  magnitude1 situated in the      
southern constellation1 ,pictor4 ,the   
rate of  its motion is over eight       
seconds of arc yearly2 and an idea of   
the vast  distance of the stars may be  
obtained by the statement that it would 
take #bjj years for the star--known as  
,gould's ,cordova ,zones1 ,v ,hour      
#bdc--to move over a space equal to the 
moon's diameter4 ,important             
observations have been made on the      
stellar motions1 and on their bearing   
on the structure of the ,universe1 by   
various astronomers1 including ,j4  ,c4 
,kapteyn and ,ludwig ,struve 7born      
#aheh71 son of ,otto ,struve2 but  these
 must be reserved for a later chapter4  
,richard ,anthony ,proctor1 born at     
,chelsea1 in ,london1 in #ahcg1         
graduated  at ,cambridge in #ahfj4 ,for 
the next twenty-eight years he earned   
his  living by publishing many volumes  
on astronomy1 popular and technical1    
fifty-seven having appeared at the time 

of his death1 which took place  at ,new 
,york on ,september #ab1 #ahhh4         
,notwithstanding the vast amount of     
work bestowed on his books1 his original
 investigations were permanent          
contributions to astronomical science4  
,in #ahgj he undertook to chart the     
directions and amounts of #afjj proper  
motions4 ,while engaged on this  work1  
it occurred to him that it would be     
8desirable and useful to  search for    
subordinate laws of motion40 ,he found1 
from the laborious  process of charting1
 that five of the seven stars of the    
,plough had a  motion in common--that is
 to say1 were moving in the same        
direction at  the same rate4 ,this      
phenomenon was termed by ,proctor       
8star-drift40 ,he  also recognised other
 instances of star-drift in other       
portions of the  heavens4    ,the       
subject was soon afterwards taken up by 
the ,french astronomer1  ,camille       
,flammarion4 ,born in #ahdb at          
,montigny-le-,roi1 in ,haute ,marne1    

,flammarion was appointed assistant to  
,le ,verrier in #aheh1 but gave up  his 
post in #ahfb4 ,employed successively at
 the ,bureau des ,longitudes1  and as   
editor of scientific papers1 he founded 
in #ahhb his private  observatory at    
,juvisy-sur-,orge1 where he has since   
continued his  investigations4          
,following up ,proctor's discovery of   
star-drift1 ,flammarion drew charts  of 
proper motions4 ,he demonstrated the    
8common proper motion0 of ,regulus  and 
an eighth-magnitude star1 ,lalande      
#ai1gdi1 from a comparison of his       
measures in #ahgg with those of         
,christian ,mayer a century previously2 
while he discovered many other          
instances4 ,his reflections on these    
motions1 as given in his #8,popular     
,astronomy1' are worthy of              
reproduction3 8,such are the stupendous 
motions which carry every sun1  every   
system1 every world1 all life1 and all  
destiny in all directions  of the       
infinite immensity1 through the         

boundless1 bottomless abyss2 in a  void 
for ever open1 ever yawning1 ever black1
 and ever unfathomable2  during an      
eternity1 without days1 without years1  
without centuries1 or  measures4 ,such  
is the aspect1 grand1 splendid1 and     
sublime1 of the  universe which flies   
through space before the dazzled and    
stupefied gaze  of the terrestrial      
astronomer1 born to-day to die          
to-morrow1 on a  globule lost in the    
infinite night40    ,measures of proper 
motion only enable us to determine the  
motion of  stars across the line of     
sight4 ,they do not tell us whether the 
star is  advancing or receding4 ,here1  
however1 the spectroscope comes to our  
aid  by means of ,doppler's principle1  
described in the chapter on the ,sun4   
,it  occurred to ,huggins that1 by      
observing the displacement of the lines 
in  the spectra of the stars1 he could  
determine their motion in the line of   
sight4 ,his first results were announced
 in #ahfh4 ,in the case of ,sirius1  the

 displacement of the line marked ,f was 
believed to indicate a  velocity of     
recession of #bi miles a second4 ,some  
time later ,huggins  announced that     
,betelgeux1 ,rigel1 ,castor1 and        
,regulus were retreating1  while        
,arcturus1 ,pollux1 ,vega1 and ,deneb   
were approaching4 ,soon after  this     
successful work the subject was taken up
 by ,maunder at ,greenwich  and by      
,vogel at ,bothkamp2 but the delicacy of
 the measurements prevented             
satisfactory results from being reached 
through visual observations1 and        
accordingly the measurements were very  
discordant4    ,in #ahhg ,h4 ,c4 ,vogel1
 working at ,potsdam ,astrophysical     
,observatory1  applied photography to   
the measurement of radial motion4       
,assisted by  ,julius ,scheiner 7born   
#aheh71 he determined the radial motions
 of  fifty-one bright stars by          
photographing the stellar spectra and   
measuring the photographs4 ,vogel found 
#aj miles a second to be the  average   

velocity of stars in the line of sight1 
the tendency of the eye  being to       
exaggerate the displacements4 ,the      
swiftest of the stars  measured by      
,vogel proved to be ,aldebaran1 with a  
velocity of recession  of #cj miles a   
second4 ,since #ahib the subject has    
been pursued by ,vogel  himself with the
 new #cj-;inch refractor at ,potsdam1 by
 ,campbell at the  ,lick ,observatory1  
,blopolsky at ,pulkowa1 and other       
observers4 ,towards  the end of #ahif   
,campbell undertook1 with the #cf-;inch 
,lick refractor1 a  series of measures  
on radial motion1 and many important    
discoveries were  made4 ,these1 however1
 must be reserved for the chapter       
dealing with  double stars4             
,herschel's great discovery1 from the   
apparent motions of the stars1 of  the  
movement of the ,solar ,system was not  
accepted by the next generation  of     
astronomers4 ,bessel declared in #ahah  
that there was absolutely no  evidence  
to show that the ,sun was moving towards

 ,hercules4 ,even ,sir ,john  ,herschel 
rejected his father's views1 although   
some confirmatory results  had been     
reached by ,gauss4 ,at length1 in #ahcg1
 ,argelander1 in a  memorable paper1    
based on his observations at ,abo1 in   
,finland1 attacked  the problem1 and    
demonstrated1 from a discussion of the  
motions of #cij  stars1 quite           
independently of ,herschel's work1 that 
the ,solar ,system was  moving towards  
,hercules4 ,this was confirmed in #ahda 
by ,otto ,struve1 in  #ahdg by ,thomas  
,galloway1 and in #ahei and #ahfc by    
,airy and ,edwin  ,dunkin 7#ahba-ahih71 
assistant at ,greenwich ,observatory4   
,meanwhile1 in #ahhf1 ,arthur ,auwers1  
permanent ,secretary of the ,berlin     
,academy of ,sciences1 completed the    
re-reduction of ,bradley's  observations
 at ,greenwich1 and brought out #cjj    
reliable proper motions1  which were    
utilised by ,ludwig ,struve1 whose      
investigation removed the  solar apex   
from ,hercules to the neighbouring      

constellation ,lyra3 this  slight change
 was confirmed by ,oscar ,stumpe1 of    
,bonn1 and ,lewis  ,boss 7born #ahdg71  
director of the ,observatory at ,albany1
 ,new ,york4 ,an  investigation by      
,newcomb fully confirmed the previous   
results4 ,in #aijj1  #aija1 and #aijb   
,kapteyn made three distinct            
investigations on the solar  motion1 and
 still further confirmed the previous   
investigations4    ,these investigations
 are fully confirmed by the application 
to the  question of ,doppler's principle
 of measuring radial motion4 ,the       
spectroscopic researches of ,campbell at
 the ,lick ,observatory place the  solar
 apex very near the position assigned to
 it by ,newcomb and ,kapteyn4  ,campbell
 finds the solar velocity to be about   
#ab miles a second1 and  ,kapteyn thinks
 a velocity of about #aa miles a second 
is 8the most  probable value that can at
 present be adopted40                   
,,chapter ,x4                           
,,the ,,light ,,of ,,the ,,stars4       

8,that a science of stellar chemistry   
should not only have become  possible1  
but should already have made material   
advances1 is assuredly  one of the most 
amazing features in the swift progress  
of knowledge our  age has witnessed40   
,so writes ,miss ,agnes ,mary ,clerke1  
the historian of  modern astronomy4 ,as 
long ago as #ahbc ,fraunhofer observed  
the spectra of  the brighter stars1 and 
gathered the first hint of the grouping 
of the  stars into three classes4 ,then1
 after ,fraunhofer's death1 the subject 
lay in abeyance for thirty-seven years4 
,at length1 in #ahfj1 on  ,kirchhoff's  
explanation of the ,fraunhofer lines1   
the study of stellar  spectra was       
inaugurated at ,florence by ,donati1 who
 carefully fixed the  positions of the  
more important lines4 ,his instrumental 
means1 however1  were very limited1 and 
his observations were not successful4   
,in #ahfb  ,rutherfurd1 in ,new ,york1  
commenced the study of stellar spectra1 
but  shortly afterwards turned his      

attention to astronomical photography4  
,the  actual founders of stellar        
spectroscopy were the eminent ,italian  
observer1 ,angelo ,secchi1 and the      
illustrious ,englishman1 ,william       
,huggins4    ,angelo ,secchi was born in
 #ahah at ,reggio1 in the ,emilia4      
,educated in the  ,collegio ,romano1 he 
was ordained priest in #ahdg1 but his   
love of  science1 and particularly      
astronomy1 dates from the beginning of  
his  career4 ,in #ahdi he succeeded ,di 
,vico as director of the ,observatory of
  the ,collegio ,romano4 ,this post he  
filled with conspicuous ability for a   
period of twenty-nine years1 until his  
death on ,february #bf1 #ahgh4 ,to      
,secchi is due the credit of the first  
spectroscopic survey of the  heavens4   
,he reviewed the spectra of #djjj stars1
 and classified them into  four distinct
 groups1 which are recognised to this   
day4 ,the first type  embraces over half
 of those which ,secchi examined4 ,this 
type is  represented by ,sirius1 ,vega1 

,altair1 and other bluish-white stars1  
and  is characterised by the intensity  
of the hydrogen lines4 ,the second type 
embraces the yellow stars1 such as      
,capella1 ,arcturus1 ,aldebaran1        
,pollux1  and the ,sun itself1 and is   
known as the ,solar type4 ,the spectra  
of these  stars closely resemble that of
 the ,sun1 and are distinguished by     
innumerable lines4 ,secchi's third type1
 or red stars1 represented by           
,betelgeux1 ,antares1 and others1 are   
characterised by strong absorption      
bands1 and the spectra have been        
described as 8fluted40 ,the third-type  
stars are comparatively scarce compared 
with the first and second1 and  the     
fourth is even less numerous4 ,the      
fourth-type stars are also red  with    
broad absorption lines4 ,to ,secchi's   
four types a fifth was added in  #ahfg  
by ,wolf and ,rayet of ,paris           
,observatory--namely1 the gaseous stars4
  ,secchi aimed at a comprehensive      
survey of the stellar spectra1 and he   

accomplished much valuable work4 ,he did
 not devote his time to analysing       
individual stars4 ,this branch of       
study--analysis of spectra and the      
determination of the elements in the    
stars--was undertaken by his            
contemporary1 ,william ,huggins1 one of 
the greatest astronomers whom  ,england 
has ever produced4    ,born in ,london  
in #ahbd1 ,william ,huggins commenced   
his astronomical  researches at the age 
of twenty-eight4 ,in #ahef he erected1  
at ,tulse  ,hill1 ,london1 an           
observatory which he equipped at great  
expense4 ,he  commenced observations on 
the usual astronomical lines1 taking    
times of  transits and making drawings  
of the surfaces of the planets4 ,but he 
soon  tired of the routine of ordinary  
astronomical work1 and on the           
publication of ,kirchhoff's explanation 
of the ,fraunhofer lines in the  solar  
spectrum1 he commenced to investigate   
the spectra of the stars4  ,having      
constructed a suitable spectroscope1 he 

commenced observations in  #ahfb in     
conjunction with his friend1 ,william   
,allen ,miller1 ,professor of           
,chemistry in ,london4 ,he exhaustively 
investigated the two red stars1         
,betelgeux and ,aldebaran1 ascertaining 
the existence in the former star  of    
sodium1 iron1 calcium1 magnesium1 and   
bismuth2 and in the latter star  the    
same elements1 with the addition of     
tellurium1 antimony1 and  mercury4      
,in #ahfc ,huggins made an attempt to   
photograph the spectra of the stars1    
and1 indeed1 obtained prints of ,sirius 
and ,capella1 but no lines were  visible
 in them4 ,in #ahgd ,draper of ,new     
,york obtained a photograph of the      
spectrum of ,vega1 showing four lines4  
,two years later ,huggins again         
attacked the problem1 and secured a     
photograph of the spectrum of ,vega1    
showing seven strong lines4 ,in #ahgi he
 was enabled to communicate             
satisfactory results of his work to the 
,royal ,society1 and since then he  has 

secured many admirable representations4 
,in #ahii the monumental work1  #8,an   
,atlas of ,representative ,stellar      
,spectra1' the joint work of ,sir       
,william and ,lady ,huggins1 was        
published4    ,in #ahgd the ,german     
,government established at ,potsdam the 
,astrophysical  ,observatory1 for the   
spectroscopic study of the ,sun and     
stars4 ,a  position on the staff was    
given to ,hermann ,carl ,vogel1 whose   
researches  in astronomical spectroscopy
 rank with those of ,secchi and         
,huggins4 ,born  in ,leipzig in #ahdb1  
he was from #ahfe to #ahfi employed in  
the ,leipzig  ,observatory4 ,called to  
,bothkamp as director in #ahgj1 he      
resigned his  post in #ahgd to accept a 
position on the staff at ,potsdam       
,observatory4  ,in #ahhb he became      
director of that ,institution1 which    
position he still  retains4    ,in #ahgd
 ,vogel revised ,secchi's classification
 of stellar spectra1 and in  #ahie he   
further improved on it4 ,his            

classification improves rather than     
supersedes the previous work of ,secchi2
 nevertheless1 he approached the        
question from a different standpoint4   
,vogel concluded in #ahgd that a        
rational scheme of stellar              
classification 8can only be arrived at  
by  proceeding from the standpoint that 
the phrase of development of the        
particular body is1 in general1 mirrored
 in its spectrum40 ,vogel divides       
,secchi's first type into three classes4
 ,in the first type1 designated         
,ia1--represented by ,sirius and        
,vega1--the metallic lines are 8very    
faint  and fine10 and the hydrogen lines
 conspicuous4 ,in ,ib no hydrogen lines 
are visible1 while in ,ic the hydrogen  
lines are bright4 ,this class  includes 
the gaseous stars4 ,in #ahie1 after the 
recognition of helium in  the stars by  
his assistant1 ,scheiner1 ,vogel        
separated the stars of class  ,ib from  
the first type altogether4 ,these stars 
are sometimes  designated as 8,type ,o10

 and sometimes as helium stars and      
,orion stars1  as the majority of the   
stars in ,orion are of that type4 ,the  
solar type  is divided into two classes1
 ,,iia being represented by the ,sun1   
,capella1 and other well-known stars1   
while ,,iib includes the ,wolf-,rayet   
stars4 ,secchi's third and fourth types 
are both classified by ,vogel as  of the
 third type4 ,these red stars were      
specially studied from #ahgh to  #ahhd  
by ,dunr at ,lund4 ,his results were    
published in a descriptive  catalogue   
which appeared at ,stockholm in #ahhd4  
,his researches related to  the spectra 
of #ceb stars1 #big of ,secchi's third  
type and #ee of his  fourth4 ,dunr is   
perhaps the greatest authority on stars 
with banded  spectra4    ,vogel's       
classification of spectra is generally  
adopted by astronomers1  although others
 have been proposed by ,lockyer and by  
,edward ,charles  ,pickering 7born      
#ahdf71 director of the ,harvard        
,observatory4 ,lockyer's  classification

 was designed to fit in with his        
8meteoritic hypothesis10  discussed in  
the chapter on ,celestial ,evolution4   
,the stars were divided  by ,lockyer    
into seven groups1 according to his     
views of their  temperature1 rising     
through gaseous stars1 red stars of     
,secchi's third  type1 and a division of
 solar stars to the ,sirian type1 and   
falling  through a second division of   
the solar type to red stars of ,secchi's
  fourth type4    ,the first            
spectroscopic star-catalogue was        
published in #ahhc by ,vogel1  assisted 
by ,gustav ,mller 7born #ahea71 a       
son-in-law of ,sprer4 ,the  catalogue   
contained details of #djea stars to the 
seventh magnitude1 and  more than half  
of these proved to be of ,secchi's first
 type4 ,vogel's  work was completed in  
different latitudes by ,dunr at ,upsala1
 and by  ,nicolaus ,thege von ,konkoly  
7born #ahdb7 at ,o',gyalla in ,hungary4 
,the famous #8,draper ,catalogue' ranks 
as the greatest catalogue of stellar    

spectra4 ,it was undertaken at ,harvard 
,observatory by ,e4 ,c4 ,pickering1 in  
the form of a memorial to ,henry        
,draper1 the successful spectroscopist4 
,commenced in #ahhf1 and published in   
#ahij1 it contains photographs of the   
spectra of no fewer than #aj1cea stars1 
down to the eighth magnitude4           
,pickering subdivided ,secchi's types   
into various classes1 the first or      
,sirian into four classes1 the second   
into eight1 while the third and  fourth 
types each constitute a separate class4 
,pickering designated his  classes by   
the capital letters of the alphabet4    
,much useful work has been done also in 
the analysis of the various  spectra4   
,julius ,scheiner1 now 8chief observer0 
at ,potsdam ,astrophysical              
,observatory1 has1 since #ahij1 done    
much valuable work in this direction4   
,special attention was devoted to the   
spectrum of ,capella1 #dij lines in  the
 spectrum of which were measured by     
,scheiner4 ,in his own words1 8he       

believes a complete proof of the        
absolute agreement between its spectrum 
and that of the ,sun to be thereby      
furnished40 ,other stars of the ,sirian 
and solar classes were exhaustively     
studied by ,scheiner4    ,the study of  
the exact brilliance of the stars was a 
branch of research  long neglected1 yet 
it is of much importance in astronomy1  
for it is  only through exact           
measurement of stellar brilliance that  
stellar  variation can be detected4     
,herschel commenced the study1 which was
  continued by his son at the ,cape1 but
 it is only within the last twenty      
years that stellar photometry has become
 a recognised branch of  astronomy2 and 
the credit of this is due to the energy 
and zeal of the  great ,american        
observer1 ,edward ,charles ,pickering4  
,born in ,boston in #ahdf1 ,edward      
,charles ,pickering was appointed in    
#ahfe  ,instructor of mathematics in the
 ,lawrence ,scientific ,school at       
,harvard1  after a distinguished        

university career4 ,in #ahgf he         
succeeded ,winlock as  director of the  
,harvard ,observatory1 and in the       
following year he  commenced his        
photometric studies4 ,he invented an    
instrument named the  meridian          
photometer1 with the aid of which he    
succeeded in determining1  in the years 
#ahgi to #ahhb1 the exact brilliance of 
#dbfj stars to the  sixth magnitude     
between the north celestial pole and    
thirty degrees of  south declination4   
,at a later date he devised a larger    
photometer1 with  which he made over one
 million observations4 ,pickering next  
extended his  survey to the southern    
hemisphere1 erecting the photometer on  
the slope  of the ,andes1 where the     
,harvard auxiliary station at ,arequipa 
is now  located1 and where #hjjj        
determinations of stellar brilliance    
were made4  ,meanwhile ,pritchard1 at   
,oxford1 published in #ahhe his         
#8,uranometria ,nova  ,oxoniensis1' with
 photometric determinations of the      

brilliance of #bghd  stars from the pole
 to ten degrees of south declination4   
,both of these  catalogues were         
epoch-making works1 and testify to the  
enthusiasm and  perseverance of the     
astronomers who designed them4    ,the  
study of stellar photometry glides into 
that of stellar variation4  ,at the     
beginning of the nineteenth century the 
number of known variable  stars was very
 small1 as a glance at the list given in
 ,brewster's  edition of ,ferguson's    
,astronomy 7#ahaa7 will show4 ,some     
remarkable  investigations were due to  
the ,english astronomer1 ,john          
,goodricke  7#agfd-aghf71 who           
rediscovered the variability of the star
 ,algol1 and  accurately determined its 
period in #aghb4 ,goodricke suggested   
that the  regular variations in the     
light of ,algol were due to the partial 
eclipse  of its light by a dark         
satellite1 a hypothesis now fully       
confirmed4 ,two  years later1 in #aghd1 
,goodricke discovered other two         

variables1  ,cephei  and  ,lyr4 ,he died
 in #aghf at the age of twenty-one1 and 
thus  variable-star astronomy was       
deprived of its founder4    ,the        
foundation of variable-star astronomy as
 an exact branch of the  science is due 
to ,argelander4 ,in the years           
#ahcg-ahde1 while residing at  ,bonn    
during the erection of the observatory1 
of which he had been made  director1 he 
erected a temporary observatory1 and    
there he carefully  determined the      
magnitudes of all stars visible in      
,central ,europe4 ,from  this he was led
 to the discussion of stellar variation1
 to which subject  he continued to give 
much attention4 ,he was the first to    
describe a  method of observing variable
 stars scientifically and accurately1--a
  method consisting in estimating in    
8steps0 or 8grades0 the difference in   
brilliance between the variable1 or     
suspected variable1 and other stars     
which are selected for comparison1 and  
which are of various degrees of         

brilliance1 so that they may be         
available for comparison with the       
variable throughout its fluctuations4   
,argelander's 8steps0 are tenths of  a  
magnitude1 and ,gore describes the      
method of observation as follows3  8,if 
we call a and b the comparison stars1   
and v the variable1 a  being brighter   
than b1 and if v is judged to be midway 
in brightness  between a and b1 we write
 a#ev#e;b4 ,if v is slightly nearer to  
b1 we write a#fv#d;b4 ,we may also write
 a#cv#g;b1 or  a#gv#c;b1 the sum of the 
steps being always ten40    ,this       
method1 described in #ahdd1 led to many 
discoveries at ,bonn in the  following  
twenty years by ,argelander and his     
assistants ,schmidt and  ,schnfeld4 ,at 
this time ,eduard ,heis 7#ahjf-ahgg71 at
 ,mnster1 who also  ranks as one of the 
founders of meteoric astronomy1 while   
engaged on the  construction of his     
great atlas1 attentively determined the 
change of  magnitude of stars visible to
 the naked eye2 and by means of the     

naked  eye1 the opera-glass1 and a small
 telescope1 he amassed a large number   
of observations4 ,at the same time two  
,english observers1 ,hind and  ,pogson1 
were making remarkable discoveries which
 greatly increased the  number of known 
variables4 ,among ,hind's discoveries   
were ,s ,cancri of the  ,algol type2    
while ,schmidt discovered another of the
 same class1  ,libr1  and also the      
famous  ,geminorum4 ,while director of  
the ,observatory of  ,mannheim1 an      
institution equipped with very          
antiquated instruments1  ,schnfeld      
devoted himself to the study of variable
 stars1 and increased  the number of    
known variables considerably4 ,in the   
southern hemisphere  ,gould1 in ,south  
,america1 did for the observation of    
variable stars what  ,argelander did in 
the northern4    ,in #ahgd a very       
important1 although not so obvious1     
service to  variable-star astronomy was 
rendered by the ,danish observer1 ,hans 
,carl  ,fredrik ,christian ,schjellerup 

7#ahbg-ahhg74 ,he translated from       
,arabic  into ,french the works of the  
,persian astronomer of a thousand years 
ago1  ,al-,sufi1 and thus rendered his  
observations available to modern        
astronomers4 ,al-,sufi was a most       
accurate observer1 and1 by comparing his
  catalogue with those of modern        
observers1 it can be found whether stars
  have changed in brilliance during the 
past thousand years4    ,the study of   
variable stars has been pursued in      
recent years by many  astronomers1 both 
by means of photography and by the      
visual method4 ,the  most important     
names in the visual discovery of        
variables are ,gustav  ,mller and ,paul 
,friedrich ,ferdinand ,kempf 7born      
#ahef7 of ,potsdam2  ,alexander ,william
 ,roberts of ,lovedale1 ,south ,africa2 
,seth ,carlo  ,chandler of ,boston2     
,nils ,christopher ,dunr at ,upsala2 and
 ,john ,ellard  ,gore 7born #ahde7 in   
,dublin4    ,the researches of ,j4 ,e4  
,gore are a brilliant example of how    

much may be  done for astronomy by means
 of very moderate instruments4 ,born in 
#ahde  at ,athlone1 in ,connaught1 he   
went to ,india in #ahfh as engineer on  
the  ,sirhind ,canal in the ,punjab4    
,while in ,india he erected his small   
telescopes on brick pillars1 and took   
observations1 many of them of  stellar  
brilliance4 ,in #ahgi he returned to    
,ireland1 and since then has  devoted   
himself to astronomy with zeal and      
enthusiasm4 ,his discoveries  and       
investigations of variables have been   
made by means of the  binocular4 ,on    
,december #ac1 #ahhe1 he discovered a   
remarkable star in  ,orion1 which was at
 first considered to be temporary1 and  
called 8,nova  ,orionis10 but was       
afterwards found to be a long-period    
variable star4    ,recently photography 
has come much to the front in the       
discovery of  variable stars4 ,pickering
 at ,harvard1 and ,wolf at ,heidelberg1 
have  particularly distinguished        
themselves in this branch1 and the      

number of  known variables is now very  
large1 as every year brings fresh       
discoveries1 mostly by aid of           
photography4 ,many of these             
newly-discovered variables are in       
star-clusters and nebul4    ,pickering  
proposed in #ahhj the following         
classification of variable  stars1 which
 has been adopted all over the          
scientific world3 ,class ,i41  temporary
 star2 ,class ,,ii41 stars undergoing in
 several months large  variations1 such 
as ,mira ,ceti and ,u ,orionis2 ,class  
,,iii41 irregular  variables1 such as   
,betelgeux and  ,herculis2 ,class ,,iv41
 short-period  variables1 such as       
,cephei1  ,geminorum1 and  ,lyr2 ,class 
,v41 8,algol  variables10 which undergo 
variations lasting but a few hours4 ,it 
is  doubtful whether new stars should be
 included in a classification of        
variables1 although in one case1 at     
least1 a new star was found to be a     
long-period variable4 ,to these a sixth 
class may now be added4 ,this  class1   

the detection of which is mainly due to 
the profound  investigations of ,gore1  
is composed of what have been termed    
8secular  variables10 which undergo slow
 fluctuations in periods of many years1 
and sometimes of centuries4 ,this ,class
 includes  ,urs ,majoris1 ,al-,fard1    
,draconis1  ,serpentis1  ,pegasi1 #hc   
,urs ,majoris1  ,piscis ,australis1     
,leonis1  ,ophiuchi1  ,crateris1 and    
others4 ,the secular variations of  some
 of these stars have been detected by   
,gore himself during the past  thirty   
years1 while in other cases he has      
detected them by comparison of  the most
 important star-catalogues1 from        
,hipparchus and ,al-,sufi down to  our  
own time4 ,in some cases the star in    
question seems to be slowly  gaining in 
brilliance1 in others slowly            
diminishing4    ,thanks to the          
application of the spectroscope1 much is
 now known of the  cause of the light   
changes in variable stars4 ,goodricke's 
theory of the  variations of ,algol was 

theoretically confirmed by the          
researches of ,e4  ,c4 ,pickering in    
#ahhj4 ,in #ahhi ,vogel proved beyond a 
doubt that the  variation in the light  
of ,algol is due to the partial eclipse 
of its  light by a dark satellite4 ,it  
was obvious to ,vogel that1 as both     
,algol  and its companion are in        
revolution round their common centre of 
gravity1 the motion of ,algol in the    
line of sight might be detected by  the 
spectroscopic method of observation4    
,vogel found that before each  eclipse  
,algol was retreating from our system1  
while on recovering it  gave signs of   
rapid approach1 proving conclusively    
that both the star  and its dark        
satellite were in revolution round their
 centre of  gravity1--,algol suffering  
partial eclipse only because the plane  
of the  orbit lies in our line of sight4
 ,algol1 therefore1 is not inherently a 
variable star1 but merely a binary4     
,following up his researches1 ,vogel1   
assuming that the bright and dark stars 

are of equal density1 arrived at  the   
conclusion that ,algol is a globe about 
one and a half million miles  in        
diameter1 the satellite equalling the   
size of the ,sun1 and the  centres of   
the stars being separated by about      
#c1bcj1jjj miles4 ,thus1  variable stars
 of the ,algol type are not variable in 
the true sense of  the word4 ,even the  
most irregular of the ,algol variables  
have been  explained4 ,perhaps the most 
irregular was ,y ,cygni1 discovered by  
,chandler in #ahhf4 ,it was soon found1 
however1 that the variations  recurred  
with great irregularity3 in less than   
two years the phases  differed by as    
much as seven hours from the predicted  
times4 ,at length  the subject was taken
 up by ,dunr at ,upsala4 ,a series of   
observations  made with the #ad-;inch   
refractor at ,upsala in #ahia and #ahib 
convinced him  in the latter year that  
two eclipses take place in the course of
 one  revolution3 one star occults the  
other4 ,dunr showed that the intervals  

between minima were thus--#a day #i     
hours2 #a day #ae hours2 #a day #i      
hours1  and so on4 ,thus1 the first1    
third1 fifth1 and seventh sets of minima
  obeyed a different law from the       
second1 fourth1 sixth1 and eighth4 ,dunr
  proved that two stars revolve round   
their centre of gravity in less than    
three days1 alternately occulting each  
other1 while the ellipticity of  the    
orbit explains the irregularity of the  
light changes4 ,in ,april #aijj  ,dunr  
gave his final conclusions as follows3  
8,the variable star ,y ,cygni  consists 
of two stars of equal size and equal    
brightness1 which move  about their     
common centre of gravity in an          
elliptical orbit1 whose major  axis is  
eight times the radius of the stars40   
,he also stated the exact  period of    
revolution and the eccentricity of the  
orbit4    ,in the case of the           
short-period variables1 such as  ,lyr1  
,cephei1   ,geminorum1 and  ,aquil1 the 
variations do not seem to be due to     

eclipse4 ,it was discovered by          
,professor ,pickering that  ,lyr is a   
spectroscopic binary1 but ,vogel and    
,keeler showed that the supposed  orbit 
is incompatible with the eclipse theory4
 ,vogel says3 8,i am  convinced that    
,lyr represents a binary or multiple    
system1 the  fundamental revolutions of 
which in #ab days #bb hours in some way 
control  the light change40 ,the eclipse
 theory1 however1 is still maintained by
  ,blopolsky1 who has framed a          
hypothesis according to which the chief 
minimum of the star's light corresponds 
with the obscuration of the  lesser     
star1 the lesser minimum with that of   
the primary1 implying that  the primary 
is much less luminous in proportion to  
its light than its  satellite1--a state 
of affairs which ,miss ,clerke concludes
 to be  improbable4    ,the variable    
stars1  ,cephei and  ,aquil1 were both  
found in #ahid by  ,blopolsky to be     
binaries2 but as the times of minimum   
light do not  correspond with those of  

eclipses in the hypothetical orbits1 he 
concludes that the variations cannot be 
explained on the eclipsing  satellite   
theory4 ,miss ,clerke is inclined to the
 theory that the  increase of luminosity
 in short-period variables is due to    
tidal action1  so that while the        
revolutions of the stars control their  
variability1  they are inherently       
unstable in light4 ,a large number of   
these stars are  known1 and it is a     
remarkable fact that the majority of    
these variables  lie on or near the     
,galaxy1 so that their variations have  
probably  something to do with their    
vicinity4    ,we now come to the        
long-period variables of which ,mira    
,ceti1  ,cygni1  and ,u ,orionis are    
examples4 ,although varying in regular  
periods1  generally of about a year1    
they are subject to remarkable          
irregularities1 so that an exact period 
cannot be assigned even to ,mira  ,ceti1
 of which the maxima are at times       
retarded and at others  accelerated with

 no apparent law4 ,the spectroscopic    
investigations of  ,campbell in #ahih   
have shown that ,mira ,ceti is a        
solitary star1 while  bright lines of   
hydrogen appear in its spectrum at      
maximum1 showing that  the variations   
are due to periodical conflagrations in 
its atmospheres4  ,in many other        
long-period variables bright lines have 
been observed4    ,a remarkable fact    
regarding these stars is the amount of  
their light  change4 ,mira ,ceti1 for   
instance1 varies from the first to the  
ninth  magnitude1 and ,u ,orionis from  
the sixth to the twelfth4 ,as ,m4       
,flammarion  says1 8the longer the      
period the greater the variation40      
,another  remarkable fact is that their 
light curves show a curious resemblance 
to  the curves of the solar spots1 only 
on a vastly greater scale1 which        
indicates that1 relatively1 these       
long-period variables are much older    
than our ,sun1 the small variations in  
the light of which are  imperceptible4  

8,here1 if anywhere10 says ,miss        
,clerke1 8will be found the  secret of  
stellar variability40    ,to the        
irregular variables no period can be    
assigned4 ,betelgeux1 in  ,orion1 the   
variation of which was noted by ,sir    
,john ,herschel in #ahdj1 is  a         
typically irregular variable4 ,but the  
most extraordinary of all  variables is 
,argus1 in the southern hemisphere1     
which is probably a  connecting link    
between variable and temporary stars4   
,the traveller  ,burchell1 from #ahaa to
 #ahae1 observed the star as of the     
second  magnitude1 but in #ahbg he noted
 it to be of the first magnitude4 ,in   
the  following year it fell to the      
second magnitude4 ,in #ahcd ,sir ,john  
,herschel noted the star to be between  
the first and second magnitude1  and in 
#ahch it rose to the first1 being equal 
to  ,centauri4 ,after a  decline1 it    
became in #ahdc equal to ,canopus1 and  
not much inferior to  ,sirius4 ,then it 
began to fade1 and in #ahfh it was only 

of the sixth  magnitude4 ,in #ahii      
,innes estimated it as #gga4 ,rudolf    
,wolf suggested a  period of #df years1 
and ,loomis #fg years2 but astronomers  
generally agree  with ,schnfeld that the
 star has no regular period4    ,the    
first temporary star of the nineteenth  
century was discovered by  ,hind1 in    
,london1 ,april #bh1 #ahdh4 ,it was of  
the fifth magnitude at  maximum1 and    
soon after began to fade1 falling to the
 tenth magnitude4  ,in #ahfj a new star 
appeared in the cluster ,messier #hj in 
,scorpio1 and  was discovered by ,auwers
 at ,knigsberg4 ,it reached only the    
seventh  magnitude4    ,on the night of 
,may #ab1 #ahff1 a new star of the      
second magnitude blazed  out in the     
constellation ,corona ,borealis4 ,it was
 first observed at ,tuam1  in ,ireland1 
by the ,irish astronomer1 ,john         
,birmingham4 ,four hours  earlier       
,schmidt had been observing that part of
 the heavens1 and it was  not then      
visible4 ,birmingham at once            

communicated the discovery to  ,huggins1
 at ,tulse ,hill1 who had commenced his 
spectroscopic  observations4 ,on ,may   
#af ,huggins observed its spectrum4 ,in 
the words of  ,miss ,clerke1 8,the star 
showed what was described as a double   
spectrum4  ,to the dusky flutings of    
,secchi's third type1 four brilliant    
rays were  added4 ,the chief of these   
agreed in position with lines of        
hydrogen2 so  that the immediate cause  
of the outburst was plainly perceived to
 have  been the eruption1 or ignition1  
of vast masses of that subtle kind of   
matter40 ,nine days after the appearance
 of the new star it was invisible  to   
the naked eye1 and afterwards fell to   
the tenth magnitude4 ,in #ahef          
,schnfeld had observed it at ,bonn as a 
telescopic star1 so that it was  not a  
8new star0 in the true sense of the     
word4    ,the next temporary star       
observed was discovered by ,schmidt1 at 
,athens1  ,november #bd1 #ahgf4 ,it was 
of the third magnitude1 situated in the 

constellation ,cygnus4 ,on ,december #b 
its spectrum was examined at ,paris  by 
,alfred ,cornu 7#ahda-aijb71 and some   
days later at ,potsdam by ,vogel  and   
,lohse4 ,it was closely similar to that 
of the new star of #ahff1  bright lines 
of hydrogen and other elements standing 
out in front of an  8absorption0        
spectrum4 ,by the end of #ahgf the star 
was of the seventh  magnitude4 ,on      
,september #b1 #ahgg1 ,nova ,cygni was  
observed at ,dunecht1 and  its spectrum 
was found to have been transformed into 
that of a planetary  nebula4 ,three     
years later1 however1 the ordinary      
stellar spectrum  reappeared4    ,a new 
star appeared in the centre of the great
 nebula in ,andromeda in  ,august #ahhe4
 ,the first announcement of the         
discovery was by ,karl ,ernst  ,albrecht
 ,hartwig 7born #ahea71 who observed the
 new star on ,august #ca2  but it had   
been previously seen by several other   
observers4 ,on ,september  #a it was of 
the seventh magnitude1 and by ,march of 

the following year  had fallen to the   
sixteenth4 ,observed by ,vogel1 ,young1 
and ,hasselberg1  the new star gave a   
continuous spectrum1 but ,huggins and   
,copeland  succeeded in discerning      
bright lines4 ,hall1 at ,washington1    
undertook a  series of measures to      
detect the parallax of ,nova ,andromed1 
but his  efforts were unsuccessful4     
,the discovery of the next temporary    
star was announced ,february #a1 #ahib1 
by the ,rev4 ,thomas ,d4 ,anderson1 a   
,scottish amateur astronomer1 in a      
post-card to the ,astronomer-,royal of  
,scotland4 ,the star was situated in    
the constellation ,auriga4 ,an          
examination of photographs1 taken at    
,harvard ,observatory1 showed that the  
new star had appeared ,december #aj1    
#ahia1 and had risen to a maximum of the
 fourth magnitude ten days later4  ,on a
 photograph taken by ,max ,wolf on      
,december #h the new star was not       
visible4 ,after ,anderson's visual      
discovery1 the spectrum of the new star 

was studied by ,copeland1 ,huggins1     
,lockyer1 ,vogel1 ,campbell1 and others4
  ,bright hydrogen lines were visible in
 the spectrum1 which appeared to be     
actually double1 giving support to the  
theory that the outburst was the  result
 of a collision between two dark bodies2
 and this was confirmed by  the         
measurements of radial motion by the    
,potsdam astronomers4    ,after ,march  
#i1 #ahib1 the new star steadily faded1 
falling to the  sixteenth magnitude on  
,april #bf4 ,but on ,august #ag ,edward 
,singelton  ,holden 7born #ahdf71       
director of the ,lick ,observatory1 and 
his  assistants1 ,schaeberle and        
,campbell1 found it of the tenth        
magnitude4 ,on  ,august #ai ,barnard    
found it transformed into a planetary   
nebula3 while  various spectroscopic    
observations of the revived ,nova       
revealed the  nebular lines4 ,by the end
 of #ahid the new star had faded to the 
eleventh  magnitude1 and early in #aija 
was observed as a minute nebula4        

,after #ahib several new stars appeared1
 and were detected on photographic      
plates by ,mrs ,fleming 7born #aheg71 of
 ,harvard ,observatory4 ,the first  of  
these1 in the southern constellation    
,norma1 was discovered in #ahic by  its 
peculiar spectrum on a ,draper          
spectrographic plate taken at ,harvard4 
,but the new star rose only to the      
seventh magnitude4 ,other new stars     
were discovered in ,carina 7,argo7 in   
#ahie1 in ,centaurus in #ahie1 in       
,sagittarius in #ahih1 and in ,aquila in
 #aijj4 ,nova ,sagittarii was1 at its   
brightest1 fully equal to ,nova ,aurig1 
and was plainly visible to the  naked   
eye1 but was never observed visually4   
,a temporary star1 appropriately        
designated 8the new star of the new     
century10 blazed out in ,perseus on the 
night of ,february #ba1 #aija4 ,it  was 
discovered independently by several     
observers3 on ,february #ba1 by         
,borisiak1 a student at ,kiev1 in       
,russia2 on the following morning1 by   

,anderson in ,edinburgh2 and on the next
 evening1 by ,gore at ,dublin1  ,nordvig
 in ,denmark1 ,grimmler at ,erlangen1   
and other observers4 ,when  first seen  
by ,anderson1 it was equal to ,algol1 of
 the second magnitude4  ,a photograph by
 ,williams at ,brighton showed that it  
must have been  fainter than the twelfth
 magnitude on ,february #bj4 ,on the    
evening of  ,february #bc the star was  
brighter than ,capella1 and was then the
  brightest star in the northern        
hemisphere4 ,on ,february #be it fell to
 the  first magnitude2 on ,march #a to  
the second1 and on ,march #f to the     
third4  ,during the spring and summer   
the light fluctuated considerably1 but  
in  ,september and ,october faded to the
 #fg magnitude4 ,in ,march #aijb it was 
of the eighth magnitude1 and in ,july   
#aijc of the twelfth4    ,the spectrum  
of ,nova ,persei was found by ,pickering
 to be of the ,orion  type on ,february 
#bb and #bc4 ,on ,february #bd the      
spectrum had become one  of the bright  

and dark lines1 and the hydrogen lines  
indicated a  velocity of #gjj to #ajjj  
miles a second4 ,measures of the sodium 
and  calcium lines1 by ,campbell and    
others1 indicated a velocity of only    
three miles a second1 so that the       
displacements of the hydrogen lines  may
 have been due to an outburst of        
hydrogen in the star4 ,the spectrum  was
 carefully studied during the spring and
 summer by ,pickering1  ,lockyer1       
,huggins1 ,vogel1 and others4 ,on ,june 
#be ,pickering reported that  the       
spectrum was slowly changing into that  
of a gaseous nebula4 ,in  ,august and   
,september #aija the nebular spectrum   
became more apparent4    ,in ,august    
#aija ,wolf at ,heidelberg discovered a 
faint trace of nebula  near the nova4   
,on ,september #bj this nebula was      
photographed by ,george  ,ritchey at the
 ,yerkes ,observatory1 and was seen to  
be of a spiral form4  ,this was         
confirmed by ,perrine1 who also found1  
from plates taken in  ,november1 that   

the nebula was moving at the rate of    
eleven minutes of  arc a year4 ,this    
extraordinary velocity was exceedingly  
puzzling to  astronomers1 and at length 
,kapteyn suggested that the nebula shone
 only  by reflected light from the new  
star1 and that the apparent motion was  
an illusion caused by the flare of the  
explosion travelling out from the  nova4
    ,on ,march #af1 #aijc1 ,herbert     
,hall ,turner 7born #ahfa71 ,professor  
of  ,astronomy at ,oxford1 discovered a 
new star of the seventh magnitude in    
the constellation ,gemini1 from an      
examination of photographic plates4     
,photographs taken at ,harvard showed   
that on ,march #a it must have been     
fainter than the twelfth magnitude1     
while five days later it was of the     
fifth4 ,in ,august #aijc ,pickering     
found its spectrum nebular4 ,in ,august 
#aije another small nova was found by   
,mrs ,fleming on the ,harvard           
photographs1 situated in ,aquila4       
,many theories have been advanced to    

account for temporary stars4            
,flammarion has shown that a body       
surrounded by a hydrogen atmosphere1 on 
grazing a dark body enveloped in oxygen1
 would produce a tremendous  explosion4 
,in #ahib ,huggins suggested that the   
outburst of ,nova ,aurig  was due to the
 near approach of two bodies with large 
velocities1  disturbances of a tidal    
nature resulting and producing enormous 
outbursts4 ,vogel suggested that the new
 star was due to the encounter of  a    
dark star with a worn-out system of     
planets2 while ,lockyer believes  all   
new stars to be due to the collision of 
swarms of meteors4 ,perhaps  the most   
probable theory is that of ,seeliger1   
which attributes these  outbursts to the
 movement of a dark body through        
nebulous matter1 which  is extensively  
diffused throughout space4 ,this theory 
explains the  changes in the spectra as 
well as the revivals of brightness which
  characterised ,nova ,aurig and the    
fluctuations of ,nova ,persei4 ,in a    

paper read to the ,royal ,society of    
,edinburgh in ,november #aijd1 the      
,german astronomer1 ,jacobus ,halm1 of  
the ,royal ,observatory1 ,edinburgh1    
extended and developed ,seeliger's      
theory1 showing also that the  necessary
 consequence of such an encounter as the
 theory assumes is the  formation of an 
atmosphere of incandescent gases1       
followed by that of a  revolving ring of
 nebulous matter4 ,in the hands of      
,halm1 therefore1  ,seeliger's theory   
leads to the nebular hypothesis as      
advanced by ,laplace  and ,herschel4    
,,chapter ,,xi4                         
,,stellar ,,systems ,,and ,,nebul4      
,the study of double stars1 commenced by
 ,herschel1 was taken up after his      
death by several of the foremost        
astronomers1 and has since been pursued 
by quite a number of observers and      
computers4 ,herschel's immediate        
successor in the study of double stars  
was his son1 who ranks only  second to  
his father as a student of stellar      

systems4 ,born at ,slough on  ,march #g1
 #agib1 ,john ,frederick ,william       
,herschel passed his childhood  8within 
the shadow of the great telescope40     
,although his early life was  spent with
 his father and aunt1 astronomy does not
 appear to have taken  up his attention 
as a boy4 ,chemistry1 however1 always   
interested him1  and1 as his aunt       
recorded1 even while a child he was fond
 of making  experiments4 ,he was        
educated at ,hitcham1 and afterwards at 
,eton4 ,he was  delicate1 however1 so   
his mother removed him from school1 and 
he was  trained at ,slough by ,mr       
,rogers1 a ,scottish mathematician4 ,at 
the age of  seventeen ,herschel entered 
the ,university of ,cambridge1 and      
,caroline  ,herschel1 who was           
exceedingly proud of him1 recorded in   
her memoirs that  he gained all the     
first prizes without exception4 ,he left
 the ,university  in #ahac4    ,john    
,herschel did not turn his attention to 
astronomy until he had  attained the age

 of twenty-four4 ,in a letter to a      
friend1 ,september #aj1  #ahaf1 he said1
 8,i am going1 under my father's        
directions1 to take up  star-gazing40   
,it was only reverence for his father   
that made him turn to  astronomy1 and he
 gave up the science he loved           
most--chemistry4 ,but his  unselfishness
 received its reward4 ,in #ahbj ,john   
,herschel constructed his  first        
reflector under his father's guidance4  
,four years previously he  had begun to 
observe double stars1 which had been for
 long studied by  his father1 who       
discovered their revolutions4 ,these    
observations were  continued from #ahba 
to #ahbc at the ,observatory of ,sir    
,james ,south  7#aghf-ahfg74 ,john      
,herschel and ,south measured #chj of   
the elder  ,herschel's double stars4    
,these investigations gained for        
,herschel and  ,south the ,lalande      
,prize of the ,french ,academy and the  
,gold ,medal of the  ,royal             
,astronomical ,society4    ,when his    

mother died ,sir ,john ,herschel decided
 to sail to the ,cape of  ,good ,hope to
 make an investigation of the stars of  
the southern  hemisphere1 which until   
then had been much neglected4 ,he was   
offered a  free passage in a ship of    
war1 but declined4 ,in ,november #ahcc  
he left  ,england1 taking with him his  
great telescopes4 ,in two months he     
arrived  at ,cape ,town1 and erected his
 astronomical instruments at            
,feldhausen1 a  short distance off4 ,in 
,october #ahce he informed his aunt that
 he had  almost completed his survey of 
the southern hemisphere4 ,during his    
8sweeps0 of the heavens he discovered   
#abjb double stars1 and #agjh nebul  and
 star-clusters4 ,in #ahch he returned to
 ,england1 and devoted the  remainder of
 his life to the publication of his     
results1 as well as to  other branches  
of science4 ,he died at ,collingwood1 in
 ,kent1 on ,may #aa1  #ahga1 at the age 
of seventy-nine4    ,john ,herschel's   
favourite objects of study were double  

stars1 of which  he discovered #ccdg in 
the northern hemisphere1 and #abjb in   
the southern4  ,he also computed several
 stellar orbits2 but the first          
calculation of a  stellar orbit was made
 by the ,french astronomer ,felix       
,savary  7#agig-ahda71 who computed the 
orbit of  ,urs ,majoris1 and found the  
period to be about sixty years4         
,contemporary with ,john ,herschel was  
his  great rival in double-star         
astronomy1 ,friedrich ,georg ,wilhelm   
,struve4  ,born at ,altona in #agic1    
,struve took his degree in #ahaa at the 
,russian  ,university of ,dorpat4 ,in   
#ahac he became director of the ,dorpat 
,observatory1 and was in #ahci promoted 
to ,pulkowa1 as director of the  great  
,observatory there1 remaining at its    
head until within three years  of his   
death1 on ,november #bc1 #ahfd4         
,struve's first recorded observation    
was on the double star ,castor4 ,in     
#ahai he commenced to measure the       
position-angles of double stars1 of     

which he published a catalogue of  #gie4
 ,in #ahbe he commenced a review of the 
heavens down to fifteen  degrees south1 
and thus discovered #bbjj previously    
unknown objects4 ,the  results were     
published in ,struve's #8,mensur        
,merometric1' which appeared  in #ahcf1 
giving the places1 distances1 colours1  
position-angles1 and  relative          
brilliance of #caab double and multiple 
stars4    ,struve's successor in this   
branch of astronomy was his son1 ,otto  
,wilhelm  von ,struve1 born in #ahai at 
,dorpat1 who became in #ahcg assistant  
to his  father1 and in #ahfa succeeded  
him as director of the ,pulkowa         
,observatory4 ,in #ahij he retired from 
this post1 settling in ,germany1 at     
,carlsruhe1 where1 on ,april #ad1 #aije1
 he died in his eighty-sixth year4      
,otto ,struve detected #ejj double      
stars1 among them  ,andromed1           
discovered in #ahdb1 and  ,equulei1     
discovered in #aheb1 within a period  of
 between five and eleven years4         

,various other astronomers have devoted 
themselves to the observation of  double
 stars1 among them ,ercole ,dembowski   
7#ahae-ahha71 of ,milan2 ,karl  ,hermann
 ,struve 7born #ahed71 son of ,otto     
,struve2 ,william ,doberck 7born        
#ahde72 ,william ,j4 ,hussey 7born      
#ahfd71 now director of the ,detroit    
,observatory2 ,camille ,flammarion2 ,n4 
,c4 ,dunr2 ,g4 ,v4 ,schiaparelli2       
,thomas ,jefferson ,jackson ,see 7born  
#ahff74 ,but the greatest living        
discoverer is ,sherburne ,wesley        
,burnham 7born #ahch71 now employed at  
the ,yerkes ,observatory1 in ,wisconsin4
 ,born in #ahch at ,thetford1 ,vermont1 
he commenced his career as a shorthand  
reporter1 studying astronomy in  his    
leisure hours4 ,with a small #f-;inch   
refractor1 mounted in a home-made       
observatory1 ,burnham commenced in #ahga
 his discoveries of double stars1  which
 soon attracted the attention of noted  
astronomers1 who permitted  him to use  
larger telescopes1 with which he        

continued his researches4  ,his first   
official appointment was in #ahhh1 when 
he became chief  assistant at the ,lick 
,observatory1 which position he resigned
 in #ahib4  ,some years later he became 
astronomer in the ,yerkes ,observatory4 
,altogether he has discovered #acjh     
double stars1 with telescopes ranging   
from a #f-;inch refractor to the        
gigantic #dj-;inch of the ,yerkes       
,observatory4    ,the computation of    
double-star orbits has been undertaken  
by various  astronomers1 among them     
,mdler1 ,klinkerfues1 ,dunr1            
,flammarion1  ,seeliger1 ,see1 ,gore1   
,burnham1 ,robert ,grant ,aitken 7born  
#ahfd7 of the  ,lick ,observatory1 and  
,giovanni ,celoria 7born #ahdb71 who    
was1 from #ahff  to #aijj1 assistant in 
the ,brera ,observatory of ,milan1 and  
since #aijj  director of that           
institution4 ,on ,june #i1 #ahij1 ,gore 
presented to the  ,royal ,irish ,academy
 a catalogue of computed binaries       
containing  reference to fifty-nine     

stars4    ,in #ahdd ,bessel discovered a
 remarkable irregularity in the proper  
motion  of ,sirius4 ,he ascribed this to
 the gravitational influence of some    
obscure body1 probably a large          
satellite4 ,in #aheg ,peters calculated 
an  orbit for the supposed satellite    
with a period of #ej years4 ,in #ahfa an
  orbit was computed by ,truman ,henry  
,safford 7#ahcf-aija71 which  indicated 
the position of the satellite4 ,close to
 this position it was  accidentally     
discovered by ,alvan ,clark             
7#ahcb-ahig71 the famous  ,american     
optician4 ,the period of the star seems 
to be about #ej years4 ,in  #ahdd       
,bessel noticed irregularities in the   
proper motion of ,procyon1 and  put     
forward the idea of a disturbing        
satellite1 as in the case of  ,sirius4  
,this was confirmed by ,mdler1 and in   
#ahgd an orbit was computed  by ,auwers1
 who found a period of #dj years4 ,in   
#ahif the satellite was  found by       
,schaeberle with the #cf-;inch refractor

 of the ,lick ,observatory4  ,a period  
of #dj years was found by ,see1 in      
agreement with the  hypothetical orbit4 
,in putting forward these theories as to
 invisible stellar satellites1  ,bessel 
remarked that 8light is no real property
 of mass10 and that the  existence of   
countless visible stars is nothing      
against the existence of  countless     
invisible and dark ones4 ,in this he    
laid the foundation of the  branch of   
science termed by ,mdler the 8,astronomy
 of the invisible40 ,in  recent years   
the astronomy of the invisible has      
become a recognised  branch of          
astronomical research1 through the      
application and  interpretation of      
,doppler's principle in spectroscopic   
observations4 ,in  the course of        
photographing the stellar spectra for   
the ,draper  ,catalogue1 ,e4 ,c4        
,pickering photographed the spectrum of 
,mizar 7 ,urs  ,majoris7 in #ahhg and   
again in #ahhi4 ,on some of these       
photographs the  line ,k was seen       

double1 while on others it was seen     
under its normal  aspect4 ,this doubling
 of the lines indicated that the star   
which we see  as single is in reality   
composed of two bodies in revolution    
round their  centre of gravity1 so close
 together that even the largest         
telescopes  cannot divide them4         
,pickering assigned a period of #ajd    
days1 but in #aija  ,vogel diminished   
this to #bj days4 ,in the same year the 
star  ,aurig was  similarly found to be 
double2 and in #ahij ,vogel1 from       
photographs taken  at ,potsdam1         
independently inaugurated the discovery 
of spectroscopic  binaries4 ,in the     
spectrum of ,spica he discovered the    
spectral lines to  be1 not doubled1 but 
periodically displaced1 indicating the  
existence of  a dark or nearly dark     
companion1 both stars revolving round   
their centre  of gravity4 ,spica was    
seen to belong to the same class as     
,algol1 only  that in the case of ,algol
 the plane of the satellite's orbit     

passes  through the ,earth and eclipses 
the star1 while in the case of ,spica   
the  orbit is inclined1 and the star is 
constant in light4    ,the line of      
research commenced by ,vogel and        
,pickering was soon followed  up by     
these investigators1 as well as by      
,blopolsky at ,pulkowa1 ,campbell  at   
the ,lick ,observatory1 ,slipher at the 
,lowell ,observatory1 and by  ,edwin    
,brant ,frost 7born #ahff71 now director
 of the ,yerkes ,observatory1  and his  
assistant1 ,walter ,adams4 ,in #ahid    
,blopolsky discovered the  duplicity of 
several variable stars1 and in #ahif    
that of ,castor1 in  ,gemini4 ,late in  
#ahif ,campbell undertook a systematic  
investigation of  radial motions1 and   
has since discovered about sixty        
spectroscopic  binaries1--among them1 in
 #ahii1 the ,pole ,star1 and in #aijj   
,capella4 ,the  latter discovery was    
made independently by ,hugh ,frank      
,newall 7born  #aheg7 at ,cambridge1 in 
,england4 ,it was found by ,campbell    

that the  revolution of the stars round 
their centre of gravity is performed in 
#ajd days2 and it soon became apparent  
that1 owing to the large size of  the   
orbit1 the duplicity of ,capella might  
be observed telescopically4 ,at         
,greenwich the star was seen to be      
elongated1 but at the ,lick ,observatory
  it was seen persistently single4      
,campbell finds that of #bhe stars      
observed by him1 more than one in nine  
is a spectroscopic binary4 ,he concludes
 that at least one star in five  or six 
will be found to be spectroscopically   
double1 and considers that  8the proven 
existence of so large a number of       
stellar systems1 differing  so widely in
 structure from the ,solar ,system1     
gives rise to a suspicion  at least that
 our system is not of the prevailing    
type of stellar  systems40    ,the study
 of triple and multiple stars is of deep
 interest1 but the  orbits of these     
objects cannot be said to be fully      
investigated by any  means4 ,the first  

application of the problem of three     
bodies to stellar  astronomy was made by
 ,seeliger in #ahhi4 ,his researches1   
relating to the  famous star1  ,cancri1 
disclosed the existence of three stars  
revolving  round a dark body1 apparently
 the most massive in the system4 ,the   
system  of  ,cancri1 at least1 seems to 
be modelled on the ,ptolemaic design4   
,in the study of star-clusters and      
nebul1 as in the investigation of       
double stars1 ,herschel's successor was 
his son4 ,his observations1 both  in    
,england and at the ,cape of ,good      
,hope1 resulted in a large number of    
new discoveries1 and the results of his 
studies in this direction were          
published in #ahfd in his catalogue of  
all known clusters and nebul1  amounting
 to #ejgi4 ,this catalogue was enlarged 
and revised in #ahhh by  ,john ,louis   
,emil ,dreyer 7born #aheb71 a ,danish   
astronomer1 but director  of the        
,observatory at ,armagh1 in ,ireland2   
and the same observer  published from   

#ahhh to #ahid a supplementary list1    
bringing the number of  known clusters  
and nebul to about #aj1jjj4    ,in the  
early part of his career1 ,john         
,herschel held firmly to the views  of  
his father of the difference between    
star-clusters and nebul1  considering   
the latter to be composed of 8shining   
fluid40 ,but he fell  off from this view
 with the resolution into stars of many 
irresolvable  nebul4 ,in #ahde ,william 
,parsons1 third ,earl of ,rosse         
7#ahjj-ahfg71  erected at ,birr ,castle1
 in ,ireland1 his great #f-;foot        
reflector1 which  still surpasses all   
other telescopes in point of size4 ,with
 this  instrument ,lord ,rosse believed 
himself to have resolved the ,crab      
nebula  in ,taurus and the ,nebula in   
,orion1 which was also said to have been
  resolved by ,bond with the #ae-;inch  
refractor at ,harvard2 and in #ahed     
,olmsted declared the 8resolution0 of   
these nebul to be the signal for  the   
renunciation of ,herschel's nebular     

theory4 ,most astronomers fell in  with 
the view that all the nebul were distant
 clusters1 which would  eventually be   
resolved into stars1 although it is only
 right to state  that the ,scottish     
astronomer1 ,john ,pringle ,nichol      
7#ahjd-ahei71 and  some other           
investigators1 held to the theory of    
,herschel4    ,the solution of the great
 problem was in #ahfd1 when on ,august  
#bi of that  year ,huggins turned his   
spectroscope on a bright planetary      
nebula in  ,draco4 ,to his amazement the
 spectrum was one of bright lines1      
proving  conclusively that the nebula   
was not a star-cluster1 but a mass of   
glowing gas1--hydrogen1 and some other  
unknown substance1 now named            
8nebulium40 ,by #ahfh ,huggins had      
observed the spectra of seventy nebul4  
,of these one-third proved to be        
gaseous1 among them the great ,orion    
nebula which ,lord ,rosse was believed  
to have resolved into stars4 ,in the    
spectrum of the latter1 the 8chief      

nebular line0 was at first ascribed  by 
,huggins to nitrogen1 but this was a    
mistake4 ,later1 it was believed  by    
,lockyer to coincide with the fluting of
 magnesium1 but this was  disproved by  
,huggins in #ahhi-ij1 and by ,keeler in 
#ahij-ia4 ,the great  nebula in         
,andromeda and the great spiral in      
,canes ,venatici were found by  ,huggins
 to display a continuous spectrum1 and a
 similar discovery was  made in regard  
to the cluster ,m #ac in ,hercules1 and 
other star-clusters4  ,in the case of   
the nebul1 it is not believed that the  
continuous  spectrum is due to the      
existence of sun-like bodies1 as a gas  
under  pressure would give a continuous 
spectrum4    ,the ,orion nebula has been
 more thoroughly studied than any other 
object  of its class4 ,the application  
of photography to spectroscopy has done 
much to further the study of the lines  
in the nebular spectrum4 ,in #ahhf      
,copeland detected in the spectrum of   
the ,orion nebula the yellow ray of     

helium4 ,on ,february #ac1 #ahij1       
,scheiner announced an important        
discovery1  namely1 the possession by   
both the nebula and the stars in        
,orion--with  the exception of          
,betelgeux--of a line1 which appeared   
bright in the  nebular spectra and dark 
in the stellar4 ,this line was          
identified by  ,vogel1 ,lockyer1 and    
others with that of helium4    ,nebular 
photography was inaugurated in #ahhj by 
,draper1 who obtained a  remarkably good
 representation of the ,orion nebula in 
that year4 ,his  work in this direction1
 cut short by his death in #ahhb1 was   
taken up by  ,janssen at ,meudon1 and by
 ,common in ,england1 who obtained1 in  
#ahhc1  several excellent photographs4  
,later photographs have shown the ,orion
  nebula to be much more extended than  
visual observations would lead one  to  
expect4 ,a photograph secured in #ahij  
by ,w4 ,h4 ,pickering revealed the      
nebulous matter in ,orion in its true   
form1 that of a gigantic spiral1        

starting from near ,bellatrix1 sweeping 
past  ,orionis and ,rigel to 1  and     
joining with the great nebula           
surrounding 2 the entire  constellation 
being thus shown to be enwrapped in     
nebulous haze4    ,in #ahhe nebular     
photography was commenced by ,isaac     
,roberts  7#ahbi-aijd71 the ,english    
amateur astronomer1 who secured         
admirable  representations of clusters  
and nebul4 ,he published1 in #ahic and  
#aijj1  two volumes of collected        
photographs of clusters and nebul4 ,this
  monumental work was thus referred to  
by ,dr ,william ,james ,lockyer3 8,dr   
,roberts has not only nobly enriched    
astronomical science1 but has raised  a 
monument to himself which will last as  
long as astronomy has any  interest for 
mankind40    ,perhaps the most          
remarkable revelation made by           
photography in this  branch of research 
has been the discovery of the nebul in  
the ,pleiades4  ,in #ahei ,tempel       
observed at ,florence an elliptical     

nebula south of the  star ,merope4 ,on  
,november #af1 #ahhe1 the brothers      
,henry obtained at ,paris  a photograph 
of the ,pleiades1 revealing the         
existence of a small spiral  nebula4    
,this was confirmed by visual           
observations1 and particularly by  the  
photographs of ,roberts1 which also     
showed the entire cluster to be         
nebulous1 and that 8the nebulosity      
extends in streamers and fleecy  masses1
 till it seems almost to fill the spaces
 between the stars1 and  to extend far  
beyond them40 ,in #ahhh a further       
advance was made by the  brothers       
,henry1 who found seven stars to be     
strung on a nebulous streak4    ,since  
#ahij nebular photography has been      
pursued by ,max ,wolf in ,germany1  and 
by ,e4 ,e4 ,barnard and ,j4 ,e4 ,keeler 
in ,america4 ,wolf's photographs of  the
 constellation ,cygnus brought out the  
close connection between the  stars and 
the extensively diffused nebulosities   
discovered by him4 ,in  #aija ,wolf     

discovered a 8nebelhaufen0 or cluster of
 nebul1 and in #aijb  published a       
catalogue of #aebh nebul round the pole 
of the ,galaxy1  showing them to be     
systematically distributed4 ,keeler made
 his memorable  observations with the   
great #cf-;inch reflecting telescope1   
which was  constructed in ,england many 
years ago by ,common4 ,it afterwards    
passed  into the hands of ,mr ,crossley 
of ,halifax1 who presented it to the    
,lick  ,observatory4 ,with this great   
instrument ,keeler commenced to take    
photographs of the heavens4 ,on one     
occasion he photographed a well-known   
nebula1 and on developing the plate was 
surprised to find seven new  nebul      
besides that which he had photographed4 
,on another occasion he  exposed a plate
 to a nebula in ,pegasus4 ,he was amazed
 to find altogether  twenty-one nebul   
included in the photograph4 ,to give    
another instance1  a plate directed to  
the constellation ,andromeda contained  
no fewer than  thirty-two nebulous      

objects4 ,this has given an enormous    
extension to our  knowledge of the      
nebul4 ,but even this is not all4       
,keeler found on his  plates numerous   
points of light which seem to be also   
nebul1 either too  small or too remote  
to appear as such4 ,apparently1 however1
 they are not  stars4 ,keeler's work    
convinced him that1 on a modest         
estimate1 there  must be at least one   
hundred and twenty thousand new nebul   
within  reach of the ,crossley          
reflector4 ,half of these1 he announced1
 were  probably spiral4 ,an idea of the 
vast importance of ,keeler's work may be
  gained if we reflect that the         
observations of all the earlier         
astronomers resulted in the discovery of
 six thousand nebul4 ,the               
investigations of ,keeler1 in all       
probability1 were the means of adding   
#abj1jjj more4    ,many observations    
have been made on nebul1 for the purpose
 of  ascertaining their proper          
motions--but without success4           

,measurements were  made by ,d',arrest  
in #aheg and by ,burnham in #ahia1 but  
none of these  revealed any motion of   
the nebul across the line of sight4     
,even the new  spectroscopic method of  
determining motions in the line of      
sight1 in the  hands of ,huggins1 failed
 in the case of the nebul4 ,with the    
great ,lick  refractor at his disposal1 
,keeler attacked the subject in #ahij1  
and  measured the radial velocities of  
ten nebul4 ,he found that the           
well-known planetary nebula in ,draco   
was moving towards the ,solar ,system   
at the rate of #dj miles a second2 for  
the ,orion nebula he found a motion  of 
recession of #aa miles a second2 but    
probably this belongs chiefly to  the   
movement of the ,solar ,system in the   
opposite direction4    ,unfortunately   
,keeler did not live to carry on his    
investigations in  nebular astronomy4   
,his early death brought to an abrupt   
end these  fruitful investigations4     
,appointed director of the ,lick        

,observatory in  #ahih1 he died suddenly
 at ,san ,francisco on ,august #ab1     
#aijj1 at the early  age of forty-two4  
,,chapter ,,xii4          ,,stellar     
,,distribution ,,and ,,the ,,structure  
,,of ,,the ,,universe4      ,after the  
death of ,herschel there was little done
 in the direction of  furthering our    
knowledge of stellar distribution1 or   
the construction of  the heavens4 ,here1
 as elsewhere1 ,herschel's immediate    
successor was his  son1 whose           
star-gauges1 both in ,england and in    
,south ,africa1 were a  worthy sequel to
 those of his father2 but ,john         
,herschel1 in his books on  astronomy1  
reproduced his father's disc-theory1    
unaware that the elder  ,herschel had   
himself abandoned it4 ,the work of the  
younger ,herschel was  entirely         
supplementary to that of his father4    
,to ,wilhelm ,struve belongs the credit 
of showing the disc-theory to be        
untenable1 and of demonstrating that    
,herschel had abandoned it4 ,this he    

was able to do after a perusal of       
,herschel's papers1 presented to him by 
,john ,herschel4 ,having demonstrated   
this1 he undertook a series of          
investigations which resulted in his    
famous theory of the ,universe4 ,this   
was published in his work #8tudes       
d',astronomie ,stellaire1' which was    
published in #ahdg4 ,his researches were
 based on the star-catalogues of        
,bessel1 ,piazzi1 and others2 and       
dealing with #eb1aii stars1 he discussed
  the number of stars in each zone of   
,right ,ascension4 ,he found1 in the    
words of ,mr ,gore1 8that the numbers   
increase from hour i to hour vi1  where 
they attain a maximum4 ,they then       
diminish to a minimum at hour  xiii1 and
 rise to another but smaller maximum at 
hour xviii1 again  decreasing to a      
second minimum at hour xxii4 ,as the    
hours vi and xviii  are those crossed by
 the ,milky ,way1 the result is very    
significant40 ,he  concluded the ,galaxy
 to be produced by a collection of      

irregularly-condensed clusters1 the     
stars condensed in parallel planes4     
,next1 he considered the ,universe as   
perhaps infinitely extended in the      
direction of the ,galaxy1 and           
accordingly he put forward the idea that
  the light from the fainter and more   
distant stars was extinguished in  its  
passage through the ether of space1     
which he regarded as imperfectly        
transparent4 ,the theory1 as ,struve    
propounded it1 was disposed of by ,sir  
,john ,herschel1 who remarked that we   
were not permitted to believe that  at  
one part of the sky our view was limited
 by extinction1 while at  another a     
clear view right through the ,galaxy    
could be had2 and by  ,robert ,grant    
7#ahad-ahib71 director of the ,glasgow  
,observatory1 who  showed that1 were the
 theory true1 the ,galaxy should present
 a uniform  appearance throughout its   
course4 ,on the whole1 ,struve's theory 
was no  improvement on ,herschel's2 for1
 as ,encke pointed out1 ,struve's theory

  was built on five assumptions1 all of 
which were questionable4    ,at the time
 of ,struve's investigation ,mdler1 at  
,dorpat1 was engaged in  an attempt to  
solve the question of the construction  
of the heavens by  quite another method1
 that of stellar proper motion4 ,he     
determined to  investigate the subject  
of proper motion in order to discover   
the  central body of the ,milky ,way4   
,if such a centre existed1 however1 the 
motions near it would be somewhat       
different from those in the ,solar      
,system4 ,in our ,solar ,system the     
planets nearest the ,sun move swiftest1 
owing to the strength of the force of   
gravitation4 ,in the ,sidereal  ,system1
 on the other hand1 the movements at the
 centre1 as ,mdler  pointed out1 would  
be slowest4 ,as there would be no very  
large  preponderating body1 the mutual  
attractions of the different stars would
  cause the bodies at the boundaries of 
the ,universe to move faster than  those
 at the centre1 the central sun--the    

object of ,mdler's search--being  in a  
state of rest relative to the ,sidereal 
,system4 ,mdler accordingly  began to   
search the heavens for a region of      
sluggish proper motions4    ,in the     
constellation ,taurus1 ,mdler noticed   
that the proper motions of  the stars   
were very slow4 ,the idea occurred to   
him that the bright red  star ,aldebaran
 might be the central sun1 but its very 
large proper  motion was obviously      
against this inference4 ,star after star
 was now  subjected by ,mdler to the    
most careful scrutiny4 ,at length1 after
 a  laborious investigation1 he         
announced that the star which fulfilled 
the  conditions of a central body was   
,alcyone1 the brightest of the          
,pleiades1  a group possessed of no     
proper motion except that due to the    
sun's drift  in the opposite direction4 
,in #ahdf ,mdler published his          
hypothesis in  his elaborate work1      
#8,the ,central ,sun4' ,he announced    
that his  observations had led him to   

the conclusion that ,alcyone occupied   
the  centre of gravity of the ,sidereal 
,system1 and was the point round which  
the stars of the ,galaxy were all       
revolving4 ,his profound imagination1   
however1 did not stop here4 ,this       
speculation led him to the sublime      
thought that the centre of the ,universe
 was the ,abode of the ,creator4 ,in    
#ahdg ,struve rejected ,mdler's theory  
as 8much too hazardous10 and this  has  
been the general opinion of astronomers4
 ,mdler's theory is now  regarded as    
quite untenable4    ,herschel's earlier 
idea that the nebul were external       
galaxies was long  held by the majority 
of astronomers1 in preference to his    
later and more  advanced ideas4 ,the    
supposed resolution of the nebul by     
,lord ,rosse's  telescope gave support  
to this external galaxy theory4 ,it was 
clearly  shown1 however1 by ,william    
,whewell 7#agid-ahff7 in #ahec1 and by  
,herbert ,spencer 7#ahbj-aijc7 in #aheh1
 that the systematic distribution  of   

the nebul in regard to the stars        
precluded the possibility of their      
being external galaxies4 ,this was      
confirmed by the spectroscopic          
discovery of the gaseous nature of some 
of the nebul1 and by the later          
researches of ,r4 ,a4 ,proctor4 ,not    
only did ,proctor make fresh            
discoveries1 but it fell to him to clear
 away the erroneous ideas  regarding the
 construction of the heavens1 and to put
 the study on a new  basis4 ,in #ahgj   
,proctor plotted on a single chart all  
the stars1 to the  number of #cbd1aih1  
contained in ,argelander's              
#8,durchmusterung' charts4  ,this work  
gave the death-blow to the              
8disc-theory40 ,in his own words1  8,in 
the very regions where the ,herschelian 
gauges showed the minutest  telescopic  
stars to be most crowded1 my chart of   
#cbd1aih stars shows the  stars of the  
higher orders 7down to the eleventh     
magnitude7 to be so  crowded1 that by   
their mere aggregation within the mass  

they show the  ,milky ,way with all its 
streams and clusterings4 ,it is utterly 
impossible  that excessively remote     
stars could seem to be clustered exactly
 where  relatively near stars were      
richly spread40    ,proctor showed also 
that in all probability the stars       
composing the  nebulous light of the    
,galaxy are much smaller than the       
brighter stars1  and not at such a great
 distance as their faintness would lead 
us to  suppose1--a conclusion confirmed 
by the work of ,celoria4 ,proctor was   
not  so fortunate in theorising as in   
direct investigation4 ,he thought that  
the ,magellanic clouds were probably    
external galaxies2 and further1 he  put 
forward the idea that the ,milky ,way is
 a spiral1 the gaps and  coal-sacks     
being due to loops in the stream1 but   
neither of these ideas  has found favour
 with astronomers4 ,but the chief work  
accomplished by  ,proctor was a revision
 of our knowledge of the ,universe1     
which he thus  describes3 8,within one  

and the same region coexist stars of    
many orders  of real magnitude1 the     
greatest being thousands of times larger
 than the  least4 ,all the nebul        
hitherto discovered1 whether gaseous and
 stellar1  irregular1 planetary1        
ring-formed1 or elliptic1 exist within  
the limits  of the ,sidereal ,system40  
,proctor's discovery of the excess of   
bright stars on the ,galaxy was         
confirmed by ,jean ,charles ,houzeau    
7#ahbj-ahhh71 director of the  ,brussels
 ,observatory4 ,some time later ,j4 ,e4 
,gore carefully examined the  positions 
of all the brighter stars in the        
northern and southern  hemisphere4      
,following this1 he made an enumeration 
of the stars in the  atlas of ,heis and 
in the charts constructed by ,harding2  
the outcome of  the investigation being 
to show that stars of each individual   
magnitude  taken separately tend to     
aggregate on the ,galaxy1 the           
aggregation being  noticed even in      
first-magnitude stars4 ,gore further    

pointed out many  cases of close        
connection between the lucid stars and  
the galactic  light4 ,a similar         
investigation was undertaken by         
,schiaparelli in #ahhi4  ,schiaparelli1 
basing his work on the catalogue of     
,gould and the  photometric measures of 
,pickering1 constructed a series of     
planispheres  which demonstrated the    
crowding of the lucid stars towards the 
plane of  the ,galaxy4 ,these           
investigations were still further       
continued by ,simon  ,newcomb1 who      
demonstrated that 8the darker regions of
 the ,galaxy are  only slightly richer  
in stars visible to the naked eye than  
other parts  of the heavens1 while the  
bright areas are between #fj and #ajj   
per cent  richer than the dark areas40  
,the ,dutch astronomer1 ,charles        
,easton1  finds a connection between the
 distribution of ninth-magnitude stars  
and  the luminous and obscure spots in  
the ,galaxy4    ,it was noticed by      
,gould1 from observations made at       

,cordova1 that 8a belt  or stream of    
bright stars appears to girdle the      
heavens very nearly in a  great circle  
which intersects the ,milky ,way40      
,according to ,gould1 the  belt includes
 ,orion1 ,canis ,major1 ,argo1 ,crux1   
,centaurus1 ,lupus1 and  ,scorpio in the
 southern hemisphere1 and ,taurus1      
,perseus1 ,cassiopeia1  ,cepheus1       
,cygnus1 and ,lyra in the northern4     
,this was interpreted by  ,celoria as   
indicating the existence of two galactic
 rings1 but ,gould  considered the zone 
of bright stars to form with the ,sun a 
subordinate  cluster of about five      
hundred stars within the ,galaxy4       
,perhaps the most elaborate             
investigations on the structure of the  
,universe have been those of ,kapteyn1  
commenced in #ahia4 ,in that year he    
demonstrated that stars are bluer and   
more easily photographed in the  ,galaxy
 than elsewhere1 a discovery            
independently made by ,gill at the      
,cape1 and ,pickering at ,harvard4 ,in  

#ahic ,kapteyn announced his            
conclusions1 derived from a novel method
 of studying the distance of the  stars 
from their proper motions4 ,in order to 
reach a definite idea of  the distances 
of the stars1 he made use of the        
component of the proper  motion1        
measured at right angles to a great     
circle of the sphere which  passes      
through a given star and the apex of the
 solar motion4 ,he found  that stars of 
the first spectral type have smaller    
proper motions than  those of the       
second1 indicating that stars of the    
second type are on the  average nearer  
to the ,solar ,system than those of the 
first1 the near  vicinity containing    
almost exclusively second-type stars4   
,kapteyn  concluded that the group of   
second-type stars formed one system1    
named  the solar cluster1 which he      
considered to be roughly spherical in   
shape4  ,in #aijb he abandoned this     
idea1 retaining1 however1 his opinions  
as to  the relative distances of the    

different types4 ,that the second-type  
stars are nearer to the ,sun than the   
first is1 he remarked in a letter  to   
the writer1 incontrovertible4    ,in the
 investigation of the motions in1 and   
extent of1 the ,universe1 the  name of  
,simon ,newcomb stands out              
pre-eminently4 ,born in #ahce at        
,wallace1  in ,nova ,scotia1 he went to 
the ,states in #ahec4 ,in #ahfb he      
received an  appointment at ,washington 
,observatory1 and he retained an        
official  position until #ahig4         
,throughout his scientific career he has
 been  specially attracted by the       
question of the construction of the     
heavens1  which he fully discussed in   
his book on #8,the ,stars' in #aija4    
,newcomb's  investigations have shown   
that some of the stars are not permanent
  members of the ,sidereal ,system1     
among them the swiftly-moving #ahcj     
,groombridge4 ,he has shown that the    
,stellar ,universe does not possess     
that form of stability which is seen in 

the ,solar ,system4 ,newcomb  considers 
the ,universe to be limited in extent1  
as opposed to the  opinions of ,struve  
and others1 who believed it to be       
infinite4 ,he has  brought clearly      
before his readers a calculation1 based 
on the known law  that there are three  
times as many stars of any given        
magnitude as of  that immediately       
brighter1 the increase of number        
compensating for the  decrease of       
brilliance4 ,were the ,universe         
infinitely extended1 the whole  heavens 
would shine with the brilliance of the  
,sun4 ,newcomb1 therefore1  concludes   
that 8that collection of stars which we 
call the ,universe is  limited in       
extent40    ,positive evidence that this
 is the case was obtained by ,giovanni  
,celoria1 now director of the ,milan    
,observatory1 in the course of a  series
 of star-gauges at the north galactic   
pole4 ,using a small  refractor1 showing
 stars barely to the eleventh magnitude1
 he found he  could see exactly the same

 number of stars as ,herschel's large   
reflector1 indicating that increase of  
optical power will not increase  the    
number of stars visible in that         
direction4 ,celoria's observation can   
only be explained on the assumption that
 the ,universe is limited in  extent1 as
 otherwise ,herschel's telescope should 
have shown more stars  than ,celoria's1 
even granting an extinction of light1--a
 theory which  ,newcomb1 ,schiaparelli1 
and others have shown to be quite       
untenable4 ,that  the ,universe is      
limited in extent is about all that is  
known for  certain1 although even this  
has been called in question1 notably by 
,e4  ,w4 ,maunder and ,h4 ,h4 ,turner4  
,the problem of the construction of the 
heavens is by no means solved1 although 
several more or less probable  theories 
have been advanced4    ,a series of     
investigations on stellar distribution1 
from #ahhd to #ahih1  led ,hugo         
,seeliger1 director of the ,munich      
,observatory1 to some  remarkable       

deductions4 ,he believes the ,universe  
to be flattened at the  galactic poles4 
,the ,galaxy is the zone of stellar     
condensation1 and he  concludes the     
distance of the ,solar ,system from the 
inner border of the  zone to be #ejj    
times the distance of ,sirius1 while the
 external border  is #aajj times that   
distance4 ,the ,universe is finite in   
extent1 its  limits being about #ijjj   
light years from the ,solar ,system4 ,in
 ,seeliger's  opinion the extinction of 
light may come into play beyond our     
,universe1  and prevent us seeing other 
collections of stars4    ,the question  
of external universes is purely a       
hypothetical one1  although there is    
undoubtedly much to be said in its      
favour4 ,these  universes have never    
been seen1 and we can only speculate as 
to their  existence4 ,the last word on  
the subject is by ,gore1 in #ahic1 in   
his  elaborate work1 #8,the ,visible    
,universe4' ,he regards the ,solar      
,system as a  system of the first order1

 and the ,galaxy and its                
fellow-universes of  the second4 ,he    
makes a calculation of the possible     
distance of an  external universe of his
 second order4 ,he assumes the distance 
of the  nearest universe from our       
,galaxy as proportional to that         
separating the  ,sun from  ,centauri1   
and reaches the amazing conclusion that 
the  distance of the nearest ,galaxy is 
no less than                            
#ebj1adi1fjj1jjj1jjj1jjj1jjj miles1--a  
distance which light1 with its          
inconceivable velocity of #ahf1jjj miles
 a second1 would take almost  ninety    
millions of years to traverse4    ,these
 calculations absolutely overwhelm the  
mind1 which is unable to  comprehend    
such vast distances4 ,our universe is   
indeed1 as ,flammarion  expresses it1 a 
point in the infinite4 ,the calculations
 of ,j4 ,e4 ,gore  represent our highest
 scientific conception of the universe4 
,he sums up  his investigations with the
 following words3 8,although we must    

consider  the number of visible stars as
 strictly finite1 the numbers of stars  
and systems really existing1 but        
invisible to us1 may be practically     
infinite4 ,could we speed our flight    
through space on angel wings beyond  the
 confines of our limited universe to a  
distance so great that the  interval    
which separates us from the remotest    
fixed star might be  considered as      
merely a step on our celestial journey1 
what further  creations might not then  
be revealed to our wondering vision8    
,systems of  a higher order might there 
be unfolded to our view1 compared with  
which  the whole of our visible heavens 
might appear like a grain of sand on    
the ocean shore1--systems perhaps       
stretching out to infinity before us1   
and reaching at last the glorious       
#8mansions' of the ,almighty1 the       
,throne  of the ,eternal40              
,,chapter ,,xiii4                       
,,celestial ,,evolution4      ,in the   
second chapter we outlined the nebular  

hypothesis as propounded  by ,herschel4 
,some time earlier the ,french          
mathematician1 ,laplace1 had  put       
forward his theory of the evolution of  
the ,solar ,system4 ,pierre  ,simon     
,laplace was born at ,beaumont-en-,auge1
 near ,honfleur1 in #agdi1 and  was     
educated in the ,military ,school of his
 native town4 ,in #agfg he  became      
,assistant ,professor of ,mathematics at
 ,beaumont1 and some years  later at the
 ,military ,school in ,paris1 which     
position he retained for  many years4   
,member of the ,institute and ,minister 
of the ,interior under  ,napoleon1 he   
was created a ,marquis by ,louis        
,,xviii41 and died at ,arcuile  on      
,march #e1 #ahbg4    ,in the last       
chapter of his popular work1 the        
#8,systme du ,monde1' ,laplace  put     
forward his nebular theory 8with that   
distrust which everything  ought to     
inspire that is not the result of       
observation or calculation40  ,laplace  
noticed that in the ,solar ,system all  

the planets revolved round  the ,sun in 
the same direction1 from west to east1  
and that the  satellites of the planets 
obeyed the same law4 ,he also observed  
that the  ,sun1 ,moon1 and planets      
rotated on their axes in the same       
direction as  they revolved round the   
,sun2 also that the planets moved round 
the ,sun1  and the satellites round     
their primaries1 in almost the same     
plane as  the ,earth's orbit1 the plane 
of the ecliptic4 ,it was evident that   
these  remarkable congruities were not  
the result of chance1 and accordingly   
,laplace expressed his belief that the  
,solar ,system originated from a  great 
nebula1 which in condensing detached    
various rings in the process  of        
rotation4 ,these rings condensed into   
the various planets and their           
satellites4    ,laplace's theory was    
powerfully supported by ,herschel's     
observations of  the various nebul in   
the heavens4 ,but1 with the supposed    
resolution of  the various nebul after  

the erection of the ,rosse reflector in 
#ahde1  the evidence in favour of the   
nebular theory seemed to be greatly     
reduced4 ,in #ahfd1 however1 the        
discovery of the gaseous nebul1 by means
  of the spectroscope1 gave further     
support to the theory4 ,powerful aid    
was lent to the nebular hypothesis by   
the famous ,german physicist1  ,hermann 
,ludwig ,ferdinand von ,helmholtz       
7#ahba-ahid71 in #ahed1 in his  theory  
of the maintenance of the ,sun's heat4  
,many theories had been  already        
advanced to account for this4 ,after the
 discovery of the  conservation of      
energy1 ,julius ,robert ,mayer1 one of  
the discoverers1  put forward the theory
 that the ,solar heat was sustained by  
the inflow  of meteorites from space1   
and this idea was developed in #ahed by 
,sir  ,william ,thomson1 now ,lord      
,kelvin 7born #ahbd71 but it was soon   
apparent that the supply of meteors     
required to sustain the ,solar heat  was
 such as would have increased the mass  

of the ,sun very considerably4          
,accordingly the hypothesis was         
partially abandoned1 and was succeeded  
by  that of ,helmholtz1 who pointed out 
that the radiation of the ,sun's heat   
was the result of its contraction       
through cooling4 ,the rate was then     
estimated at #chj feet yearly1 or a     
second of arc in #fjjj years4 ,this     
theory was at once generally accepted4  
,it assumes the ,sun to be still        
contracting1 and therefore1 on going    
backwards in imagination1 we reach  a   
period when the ,sun must have been much
 larger than now1 and1 in fact1         
extended beyond the orbit of ,neptune4  
,several objections to ,laplace's       
nebular theory were urged by various    
investigators4 ,among these was the     
retrograde motions of the satellites  of
 ,uranus and ,neptune1 and the extremely
 rapid revolution of the inner          
satellite of ,mars4 ,other objections   
were urged by ,babinet1 ,kirkwood1 and  
others1 and at length a sweeping reform 

of the nebular theory was  proposed by  
,faye in #ahhd1 in his work1 #8,sur     
l',origine du ,monde4' ,faye  put       
forward the idea that all the planets   
interior to the orbit of  ,uranus were  
formed inside the solar nebula1 while   
,uranus and ,neptune  came into         
existence after the development of the  
,sun was far advanced4  ,but the        
objections to ,faye's theory are        
formidable1 and the hypothesis  has not 
been accepted4    ,a popular exposition 
of the nebular theory was given in #aija
 in ,ball's  work on #8,the ,earth's    
,beginning4' ,he exhaustively discusses 
the whole  question1 and explains the   
retrograde motion of the satellites of  
,uranus  and ,neptune as due to the fact
 that the planes of the orbits of the   
satellites will eventually be brought to
 coincide with the ecliptic4  ,these    
motions1 says ,ball1 do not disprove the
 nebular theory4 8,they  rather         
illustrate the fact that the great      
evolution which has wrought  the ,solar 

,system into its present form has not   
finished its work3 it is  still in      
progress40    ,the theory that the      
,sun's heat was maintained by meteors1  
was extended  by ,proctor in #ahgj to   
explain the growth of the planets       
through meteoric  aggregation as well as
 nebular condensation4 ,certainly the   
theory1 as  developed by ,proctor1      
accounted fairly well for the various   
features of  the ,solar ,system2 but the
 highest development of the meteoritic  
theory  is due to ,lockyer1 who         
published his views in #ahij1 in his    
work1 #8,the  ,meteoritic ,hypothesis4' 
,lockyer claims that his views are      
merely  extensions of ,schiaparelli's   
ideas regarding the concentration of    
celestial matter4 ,he considered the    
chief nebular line to be identical  with
 the remnant of the magnesium fluting1  
which is conspicuous in  cometic and    
meteoric spectra2 but ,huggins and      
,keeler1 with more powerful             
instruments1 disproved the supposed     

coincidence4 ,lockyer considers that    
8all self-luminous bodies in the        
celestial space are composed either of  
swarms of meteorites or of masses of    
meteoric vapour produced by heat4  ,the 
heat is brought about by the            
condensation of meteor swarms1 due to   
gravity1 the vapour being finally       
condensed into a solid globe40          
,lockyer divided the stars into seven   
groups1 according to temperature1  the  
order of evolution being from red stars 
through a division of  second-type stars
 to ,sirian stars1 regarded as the      
hottest stars2  through a second        
division of solar stars to fourth-type  
stars4 ,in fact1  the theory aspires to 
give a complete explanation of all      
celestial  phenomena1 from meteors to   
nebul4 ,newcomb1 however1 considers that
 the  objections to the theory are      
insuperable1 and his opinion is shared  
by  the majority of astronomers1 many of
 whom1 however1 consider that there  are
 elements of truth in the theory2 but   

,lockyer undoubtedly carried his  ideas 
to an extravagant extent4    ,lockyer's 
evolutionary order of the stars is not  
supported by ,vogel4  ,zllner suggested 
in #ahfe that yellow and red stars are  
simply white  stars in a further stage  
of cooling2 but ,angstrm showed that    
atmospheric composition is a safer      
criterion of age than colour4 ,vogel's  
classification1 first published in      
#ahgd1 and further developed in #ahie1  
is from the standpoint of evolution4 ,he
 considers ,orion stars and ,sirian     
stars to be the youngest orbs4 ,solar   
stars are considered by ,vogel to  have 
wasted much of their store of radiation1
 and red stars are viewed  as 8effete   
suns1 hastening rapidly down the road to
 final extinction40  ,he considers stars
 of ,secchi's fourth type to be also    
dying suns1 both  types representing    
alternative roads for stars of the      
,solar type in  their decline into dark 
stars4 ,this view is supported by ,dunr1
 and is  distinctly confirmed by ,hale's

 observations with the ,yerkes          
telescope4  ,vogel's views1 in fact1 are
 generally accepted among astronomers4  
,the  nebular theory1 modified by       
subsequent research1 seems destined to  
hold  its own against all attacks4      
,distinctly supplementary to the nebular
 theory are the remarkable  researches1 
commenced in #ahgi1 by ,sir ,george     
,howard ,darwin 7born  #ahde71 son of   
,charles ,darwin the great biologist4   
,george ,howard ,darwin  was born in    
#ahde1 at ,downe in ,kent1 was educated 
at ,cambridge1 and  studied for the law2
 but in #ahgc he returned to ,cambridge1
 where he  became ,plumian ,professor of
 ,astronomy in #ahhc4 ,in #ahgi he      
communicated  to the ,royal ,society the
 first of his papers on tidal friction1 
which  were summed up in his book on    
#8,the ,tides1' published in #ahih4 ,he 
finds  that the tides act upon the      
,earth as a brake does upon a           
machine1--they  tend to retard its      
rotation4 ,consequently1 the day is     

growing longer1  the ,moon's orbit is   
becoming enlarged1 and its period of    
revolution is  being lengthened4    ,at 
present the day is about twenty-four    
hours long1 and the month about         
twenty-seven days4 ,the day1 however1   
will be lengthened at a more rapid  rate
 than the month1 and in the remote      
future the day and month will  both last
 fifty-five of our present days4 ,the   
,moon will revolve round  the ,earth in 
the same period that the ,earth rotates 
on its axis1 and the  two bodies will   
perform their circuit round the ,sun as 
if united by a  bar4    ,not only can we
 foresee the future of the ,earth-,moon 
,system1 but we can  also read the past4
 ,according to ,darwin's theory1 the    
,earth1 in the  remote past1 was        
probably rotating on its axis in a very 
short period1  between three and five   
hours4 ,the ,moon must then have been   
much nearer  us than it is now1 and was 
probably revolving round its primary in 
the  same period that the ,earth took to

 rotate on its axis4 ,the two globes1   
then gaseous1 must have been revolving  
almost in actual contact4 ,had the      
month been even a second shorter than   
the day1 the ,moon must inevitably  have
 fallen back on the ,earth4 ,as it was1 
the condition of affairs could  not     
endure4 ,the condition of the ,moon     
resembled that of an egg balanced  on   
its point4 ,the ,moon must either recede
 from the ,earth or fall back  upon it4 
,the solar tide here interfered1 and    
caused the ,moon to recede  from its    
primary until it reached its present    
distance of #bci1jjj miles4    ,the fact
 that the ,earth and ,moon were almost  
in contact suggests that  they were     
probably in contact4 ,in other words1   
the ,moon originally  formed part of the
 ,earth1 which1 in consequence of its   
short-rotation  period1 and probably    
also owing to the interference of the   
solar tide1  split into two portions1   
and the smaller of these now forms the  
,moon4 ,it  is likely that the matter   

now forming the ,moon was detached from 
the  ,earth in separate particles4 ,just
 as the tides raised by the ,moon tend  
to retard the motion of the ,earth1 so  
the ,earth tides raised in the ,moon    
have already done their work4 ,the ,moon
 now rotates on its axis in the  same   
time as it revolves round the ,earth4   
,part of the evolution of the           
,earth-,moon system is completed4       
,schiaparelli's discovery that the      
rotation periods of both ,venus and     
,mercury coincide with their times of   
revolution is distinctly confirmatory of
 ,darwin's theory4    ,in his chapter on
 the 8,evolution of ,celestial ,systems0
 in his book on  #8,the ,tides1' ,darwin
 discusses the distribution of the      
satellites of the  ,solar ,system4 ,he  
says of the evolution of a planet3 8,we 
have seen that  rings should be shed    
from the central nucleus when the       
contraction of  the nebula has induced a
 certain degree of augmentation of      
rotation4  ,now1 if the rotation were   

retarded by some external cause1 the    
genesis  of a ring might be retarded or 
entirely prevented40 ,he then remarks   
that  probably the formation of the     
,moon was retarded1 and in the case of  
,mercury and ,venus1 solar tidal        
friction prevented satellite formation4 
,this explains why ,mercury and ,venus  
have no satellites1 the ,earth only     
one1 ,mars two1 while the exterior      
planets have each several satellites4   
,the theory of tidal friction was       
extended in #ahib to the explanation of 
the double stars by the ,american       
astronomer1 ,see4 ,see showed by        
mathematical calculation the effects of 
tidal friction in shaping the  eccentric
 orbits of the binary stars1 the course 
of evolution being  traced from double  
stars1 revolving almost in contact1     
which the  spectroscope reveals1 to the 
telescopic doubles4 ,see's researches   
have  done much to supplement those of  
,darwin1 who considers that there are   
two types of cosmical evolution1--the   

,laplacian1 and the 8second0 or  lunar  
type4    ,lowell1 in his work on #8,the 
,solar ,system' 7#aijc71 adds six       
congruities  to those remarked by       
,laplace and his successors4 ,these are1
 8,all the  satellites turn the same    
face to their primaries 7so far as we   
can  judge72 ,mercury1 and probably     
,venus1 do the same to the ,sun2 one law
  governs position and size in the      
,solar ,system and in all the satellite 
systems2 orbital inclinations in the    
satellite systems increase with         
distance from the primary2 the outer    
planets show a greater tilt of axis  to 
orbit-plane with increased distance from
 the ,sun 7so far as  detectable72 the  
inner planets show a similar relation40 
,the fate of the average solar star is  
sketched out by ,vogel's                
classification1 and by any evolutionary 
hypothesis which we may adopt4  ,in the 
words of ,lowell3 8,though we cannot as 
yet review with the mind's  eye our     
past1 we can1 to an extent1 foresee our 

future4 ,we can with  scientific        
confidence look forward to a time when  
each of the bodies  composing our ,solar
 ,system shall turn an unchanging face  
in perpetuity  to the ,sun4 ,each will  
then have reached the end of its        
evolution set in  the unchanging stare  
of death4 ,then the ,sun itself will go 
out1 becoming  a cold and lifeless mass2
 and the ,solar ,system will circle     
unseen1  ghostlike1 in space1 awaiting  
only the resurrection of another cosmic 
catastrophe40    ,as to what this cosmic
 catastrophe will be1 science gives no  
definite  idea2 nor can astronomers say 
with certainty whether the ,universe    
will  come to an end by the extinction  
of its luminaries1 or whether the suns  
and planets will be brought back to     
luminosity again2 but the human mind    
shrinks from the idea of a dead         
,universe4 ,at this point science has   
said  its last word1 and must give place
 to religion4 ,in our day we may repeat 
with deeper meaning the words of the    

,scottish astronomer1 ,thomas ,dick3    
8,here imagination must drop its wing1  
since it can penetrate no further  into 
the dominions of ,him who sits on the   
,throne of ,immensity4  ,overwhelmed    
with a view of the magnificence of the  
,universe1 and of the  perfections of   
its ,almighty ,author1 we can only fall 
prostrate in deep  humility and exclaim1
 #8,great and marvellous are ,thy works1
 ,lord ,god  ,almighty4'0               
,,index4                                
,a    ,absolute parallax1 #aeh4         
,adams1 ,j4 ,c41 #gh1 #aaf1 #aag1 #aah1 
#aai1 #abj1 #adj4    ,adams1 ,w41 #bje4 
,aerolites1 #adg1 #adh1 #adi4    ,airy1 
,sir ,g4 ,b41 #bg1 #ajd1 #aag1 #abj4    
,aitken1 ,r4 ,g41 #bjb4    ,alcyone 7   
,tauri71 #bag4    ,aldebaran 7 ,tauri71 
#aea1 #aff1 #agj1 #agb4    ,algol 7     
,persei71 #agh1 #ahb1 #ahc1 #ahd1 #aic1 
#bjd4    ,al-,sufi1 #ahj1 #ahc4         
,altair 7 ,aquil71 #agj4    ,anderson1  
,t4 ,d41 #aia1 #aib4    ,andromeda      
nebula1 #ahj1 #bjh4    ,andromed 771    

#bja4    ,andromed 7,nova71 #ahj4       
,andromedid meteors1 #adb1 #adi4        
,angstrm1 ,a4 ,j41 #ej1 #ea4    ,antares
 7 ,scorpii71 #aga4    ,aquila1 #aie4   
,aquil 771 #ahe1 #ahf4    ,arago1 ,f4   
,j4 ,d41 #f1 #aa1 #ca1 #cg1 #dj1 #aah1  
#abj1 #abi4    ,arcturus 7 ,bootis71    
#afe1 #agj4    ,arequipa ,observatory1  
#ge4    ,argelander1 ,f4 ,w4 ,a41 #bg1  
#aei1 #afg1 #agh1 #agi1 #ahj1 #bah4     
,argo ,navis1 #bba4    ,argus 771 #ahg1 
#ahh4    ,armagh ,observatory1 #bjf4    
,asteroids1 #ai1 #fb1 #ig-ajb4          
,astronomer-,royal of ,scotland1 #acd1  
#aee1 #aia2        of ,england1 #ei1    
#ag2        of ,ireland1 #aea1 #aef4    
,astronomy of the invisible1 #bjc4      
,aurig 7,nova71 #aia1 #aib1 #aie4       
,auwers1 ,a41 #afg1 #ahh1 #bjc4         
,b    ,babinet1 #bcj4    ,baily1 ,f41   
#aei4    ,bakhuyzen1 ,h4 ,g41 #ia4      
,ball1 ,sir ,r4 ,s41 #bc1 #cd1 #ajh1    
#ada1 #adi1 #aef1 #aeh1 #bcj4           
,barnard1 ,e4 ,e41 #ai1 #ie1 #ajg1 #ajh1
 #aaj1 #aaa1 #aac1 #acf1 #aia1 #baa4    

,beer1 ,w41 #fh1 #fi1 #ij4    ,bellatrix
 7 ,orionis71 #bji4    ,blopolsky1 ,a41 
#hg1 #aaj1 #aff1 #ahe1 #ahf1 #bjd1 #bje4
    ,berlin ,observatory1 #aai1 #abj4   
,bessel1 ,f4 ,w41 #bd1 #hb1 #aaf1 #aea1 
#aeb1 #aec1 #aed1 #aei1 #afg1 #bjb1     
#bjc4    ,betelgeux 7 ,orionis71 #afe1  
#aga1 #agb1 #ahb1 #ahg4    ,biela1 ,w41 
#abh4    ,biela's comet1 #abh1 #abi1    
#adb1 #adc1 #adf1 #adi4    ,birmingham1 
,j41 #ahi4    ,bode1 ,j4 ,e41 #ig1 #ih1 
#aeb4    ,bode's ,law1 #ig4             
,boeddicker1 ,o41 #gg4    ,bond1 ,g4    
,p41 #ajc1 #aji1 #acj1 #acf1 #bjg4      
,bond1 ,w4 ,c41 #aji1 #aab1 #abj4       
#8,bonn ,durchmusterung1' #aei1 #afj1   
#bah4    ,bonn ,observatory1 #hh1 #ig1  
#afj4    ,botis 771 #cj4    ,borisiak1  
#aib4    ,boss1 ,l41 #afh4    ,bouvard1 
,a41 #aae1 #aaf4    ,bradley1 ,j41 #aei1
 #afg4    ,brdikhine1 ,t4 ,a41 #aje1    
#aca1 #acb1 #acc1 #acd1 #ace4           
,brewster1 ,sir ,d41 #ej1 #aja1 #agh4   
,brinkley1 ,j41 #aea4    ,brnnow1 ,f41  
#aef4    ,bruno1 ,g41 #ce4    ,buffon1  

#ajc4    ,bunsen1 ,r4 ,w41 #ea4         
,burchell1 #ahh4    ,burnham1 ,s4 ,w41  
#bja1 #bjb1 #bab4                       
,c    ,callandreau1 ,o41 #acf4          
,callandrelli1 #aea4    ,cambridge      
,observatory1 #aaf4    ,campbell1 ,t4   
7,poet71 #b4    ,campbell1 ,w4 ,w41 #bd1
 #ajg1 #aaj1 #aff1 #afh1 #ahg1 #aia1    
#aic1 #bjd1 #bje4    ,canals of ,mars1  
#ia1 #ib1 #ic1 #id1 #ie4    ,cancri 771 
#bjf4    ,cancri 7,s71 #ahj4    ,canis  
,major1 #ahh4    #8,cape                
,durchmusterung1' #afa1 #afb4    ,cape  
,observatory1 #aee1 #aeg4    ,capella 7 
,aurig71 #agj1 #agf1 #aic1 #bje4        
,carnera1 ,l41 #ajj4    ,carpenter1 ,j41
 #gc4    ,carrington1 ,r4 ,c41 #de1 #df1
 #ei4    ,cassini1 ,d41 #ba4            
,cassiopeia1 #bba4    ,castor 7         
,geminorum71 #cj1 #bjj1 #bje4           
,celoria1 ,g41 #bjb1 #bah1 #bba1 #bbc1  
#bbd4    ,centauri 771 #aee1 #ahh1 #bbe4
    ,centaurus1 #bba4    ,cephei 771    
#agh1 #ahb1 #ahe1 #ahf4    ,cepheus1    
#bba4    ,ceres1 #ai1 #ih1 #aja4        

,cerulli1 ,v41 #hf1 #ia1 #id4           
,chacornac1 #afa4    ,challis1 ,j41     
#aaf1 #aai1 #abj4    ,chambers1 ,g4 ,f41
 #ca4    ,chandler1 ,s4 ,c41 #hh1 #hi1  
#aha1 #ahd4    ,chladni1 ,e41 #ach4     
,chromosphere1 solar1 #ee1 #ef4         
,clark1 ,a41 #bjb4    ,clerke1 ,miss ,a4
 ,m41 #c1 #e1 #h1 #ab1 #ac1 #ae1 #be1   
#bf1 #cd1 #db1 #eh1 #ge1            #hf1
 #ib1 #aje1 #aji1 #abd1 #abe1 #aca1     
#acb1 #acc1 #adj1 #adb1 #afi1           
#ahf1 #ahg1 #ahi4    ,clerk-,maxwell1   
,j41 #aji1 #aaj4    ,coggia's comet1    
#aca1 #acb1 #acc4    ,comet families1   
#ace4    ,comets1 #bd1 #abc-acg1 #ada1  
#adb1 #adc1 #add1 #adf1 #adi1 #aeb4     
,common1 ,a4 ,a41 #ajg1 #bji4           
,copeland1 ,r41 #acd1 #ace1 #aij1 #bjh4 
,cornu1 ,a41 #ahi4    ,corona ,borealis1
 #ahh4    ,corona1 solar1 #ee1 #eg1 #fd4
    ,coron 7,nova71 #ahh1 #ahi4         
,crossley1 ,e41 #baa4    ,crux1 #bba4   
,cygni 7#fa71 #aeb1 #aeh4    ,cygni     
7,y71 #ahd1 #ahe4    ,cygni 7,nova71    
#ahi1 #aij4    ,cygnus1 #aeb1 #ahi1     

#bba4                                   
,d    ,damoiseau1 #gh4    ,d',arrest1   
,h4 ,l41 #if1 #aai1 #adb1 #bab4         
,dartmouth ,observatory1 #ef4           
,darwin1 ,sir ,g4 ,h41 #bcc1 #bcd1 #bce1
 #bcf4    ,dawes1 ,w4 ,r41 #ij1 #aag4   
,de la ,rue1 ,w41 #eb1 #ge4             
,delaunay1 ,c4 ,e41 #gh1 #gi4           
,dembowski1 ,e41 #bja4    ,deneb 7      
,cygni71 #afe4    ,denning1 ,w4 ,f41    
#hd1 #he1 #ia1 #ie1 #aje1 #aaa1 #aab1   
#add1 #ade1 #adf4    ,deslandres1 ,h41  
#aaj4    ,dick1 ,t41 #he1 #bch4         
,disc-theory1 #cb1 #cf1 #ch1 #ci1 #bad1 
#bah4    ,di ,vico1 ,f41 #he1 #hf1 #agj4
    ,doberck1 ,w41 #bja4    ,donati1 ,g4
 ,b41 #acj1 #aca1 #afi4    ,donati's    
comet1 #acj1 #acc1 #acf4    ,doppler1   
,c41 #eg1 #eh4    ,doppler's ,principle1
 #eh1 #ei1 #hg1 #aaj1 #afe1 #afh1 #bjc4 
,douglass1 ,a4 ,e41 #ib1 #ajg4          
,draconis 771 #ahb4    ,draper1 ,h41    
#acf1 #agb1 #age4    ,dreyer1 ,j4 ,l4   
,e41 #bjf4    ,dunecht ,observatory1    
#aeg4    ,dunr1 ,n4 ,c41 #eh1 #ei1 #agd1

 #age1 #aha1 #ahd1 #ahe1 #bja1 #bjb1    
#bcc4    ,dunkin1 ,e41 #bg1 #afg4       
,dunsink ,observatory1 #aef4            
,e    ,earth1 #gf1 #ig1 #ajc1 #ajd1     
#adg1 #adh1 #adi1 #aec1 #aed1 #aef1     
#bcf4    ,earth-,moon system1 #bcd1     
#bce4    ,easton1 ,c41 #bba4            
,eclipses1 lunar1 #gg4    ,eclipses1    
solar1 #ef1 #eg1 #hj1 #ha4    ,edinburgh
 7,royal7 ,observatory1 #aie4           
,electrical repulsion theory1 #abf4     
,elger1 ,t4 ,g41 #gd4    ,elkin1 ,w4    
,l41 #aeg4    ,encke1 ,j4 ,f41 #cj1 #fa1
 #aai1 #abg1 #abh1 #baf4    ,encke's    
comet1 #abg1 #abh1 #acg4    ,erman1     
#adj4    ,eros1 #fb1 #aja4    ,ertborn1 
#he4    ,euler1 ,l41 #hh1 #hi4          
,evolution1 planetary1 #bbh1 #bbi1 #bcj1
 #bca4    ,evolution1 stellar1 #cc1 #cd1
 #bca1 #bcb4                            
,f    ,faye1 ,h41 #fj1 #abi1 #bcj4      
,faye's comet1 #abi1 #acg4    ,ferguson1
 ,j41 #i1 #agh4    ,flammarion1 ,c41    
#hg1 #ia1 #ie1 #aba1 #adg1 #afd1 #ahg1  
#aie1 #bja1 #bjb1            #bbf4      

,flamsteed1 ,j41 #e4    ,fleming1 ,mrs1 
#aib1 #aie4    ,forbes1 ,g41 #abb4      
,fraunhofer1 ,j4 #dg1 #dh1 #di1 #ej1 #c1
 #aea1 #aec1 #afi4    ,fraunhofer lines1
 #dh1 #di1 #ej1 #ea1 #afi1 #agb4        
,frost1 ,e4 ,b41 #bje4                  
,g    ,galactic poles1 #ce1 #bbd4       
,galaxies1 external1 #cb1 #bah1 #bbe1   
#bbf4    ,galaxy1 or ,milky ,way1 #cb1  
#cf-db1 #ahf1 #baa1 #bae1 #baf1 #bag1   
#bai1            #bbj1 #bba1 #bbd1 #bbe4
    ,galileo1 #dd1 #ajg4    ,galle1 ,j4 
,g41 #fb1 #ajh1 #aji1 #aai1 #adb4       
,galloway1 ,t41 #afg4    ,gambart1 #abh4
    ,gauss1 ,c4 ,f41 #bg1 #ih1 #afg4    
,gautier1 ,a41 #de4    ,gemini1 #aa1    
#aid4    ,geminorum 7,nova71 #aid4      
,geminorum 771 #ahj1 #ahb1 #ahe4        
,george ,,iii41 #aa1 #bc4    ,gill1 ,sir
 ,d41 #fb1 #acf1 #aee1 #aeg1 #afj1 #afa1
 #bba4    ,glasgow ,observatory1 #baf4  
,goodricke1 ,j41 #agh1 #ahc4    ,gore1  
,j4 ,e41 #bd1 #ch1 #agi1 #aha1 #ahb1    
#ahc1 #aib1 #bjb1 #bae1 #bbj1 #bbe1     
#bbf4    ,gould1 ,b4 ,a41 #ace1 #afj1   

#afc1 #ahj1 #bbj1 #bba4    ,grant1 ,r41 
#baf4    ,gravitation1 law of1 #bi4     
,greenwich ,observatory1 #ei1 #aag4     
,grimmler1 #aib4    ,groombridge        
7#ahcj71 #aef1 #afb1 #bbc4              
,groombridge 7#afah71 #aef4             
,gruithuisen1 #hg4                      
,h    ,hale1 ,g4 ,e41 #ee1 #eg1 #bcc4   
,hall1 ,a41 #if1 #aaa1 #aab1 #aef1 #aij4
    ,hall1 ,maxwell1 #aba4    ,halley1  
,e41 #ach4    ,halley's comet1 #abc1    
#acj1 #aeb4    ,halm1 ,j41 #aie1 #aif4  
,hansen1 ,p4 ,a41 #fa1 #gh1 #gi4        
,hansky1 ,a41 #eg4    ,harding1 ,k4 ,l41
 #ii1 #aec1 #bbj4    ,hartwig1 ,e41     
#aij4    ,harvard ,observatory1 #agd1   
#age1 #aia4    ,hasselberg1 ,b41 #adh1  
#aij4    ,heis1 ,e41 #agi1 #bbj4        
,heliometer1 #aec1 #aeg4    ,helium     
stars1 #agd4    ,helmholtz1 ,h41 #fa1   
#bbi4    ,hencke1 ,k4 ,l41 #ii4         
,henderson1 ,t41 #aed1 #aee4    ,henry1 
,paul and ,prosper1 #ajj1 #aad1 #baj4   
,hercules1 #afg4    ,herculis 771 #ahb4 
,herculis 771 #bf4    ,herschel1        

,william1 #a-db1 #dc1 #fj1 #fc1 #fe1    
#fi1 #gd1 #gg1 #he1 #ij1 #ii1           
#ajc1 #aji1 #aaa1 #aab1 #aae1 #abc1     
#aej1 #afb1 #afg1 #agf1 #aif1           
#aig1 #bjg1 #bad1 #baf1 #bah1 #bbd1     
#bbg4    ,herschel1 ,a41 #add4          
,herschel1 ,caroline1 #f1 #h1 #i1 #ab1  
#ac1 #ad1 #cj1 #ce1 #abg1 #aih4         
,herschel1 ,sir ,j41 #d1 #ag1 #bg1 #cj1 
#cg1 #ej1 #aab1 #aac1 #abj1 #acj1 #add1 
#afg1 #ahg1 #ahh1 #aig1 #aih1 #aii1     
#bjj1 #bad1 #bae4    ,hind1 ,j4 ,r41    
#ii1 #abi1 #ace1 #ahj1 #ahh4    ,hoek1  
#ace4    ,holden1 ,e4 ,s41 #aia4        
,hough1 ,g41 #aje4    ,houzeau1 ,j4 ,c41
 #bbj4    ,huggins1 ,lady1 #agb4        
,huggins1 ,sir ,w41 #ed1 #eg1 #gd1 #ie1 
#ajf1 #aad1 #aca1 #acf1 #afe1 #agj1     
#aga1 #agb1 #agc1 #ahi1 #aij1 #aia1     
#aic1 #aie1 #bjg1 #bjh1 #bab1           
#bca4    ,humboldt1 ,a41 #dd1 #aci4     
,hussey1 ,w4 ,j41 #aaf1 #bja4           
,i    ,innes1 ,r41 #ahh4                
,intra-,mercurial planet1 #hj1 #ha4     
,italian spectroscopists1 #ed1 #ee4     

,j    ,janssen1 ,p4 ,j4 ,c41 #eb1 #ec1  
#ed1 #eg1 #ei1 #aab1 #bji4    ,juno1    
#ai1 #ii1 #aja4    ,jupiter1 #bj1 #ge1  
#ig1 #aja-ajh1 #aab1 #aad1 #aba1 #abb1  
#ace1 #add1 #adf4    ,juvisy            
,observatory1 #afd4                     
,k    ,kaestner1 #fe1 #abd4    ,kaiser1 
,f41 #ij4    ,kant1 ,i41 #cd1 #ce1 #aja1
 #ajc4    ,kapteyn1 ,j4 ,c41 #bg1 #aeh1 
#afa1 #afb1 #afh1 #bba1 #bbb4           
,keeler1 ,j4 ,e41 #ie1 #aad1 #ahe1 #bjh1
 #baa1 #bab1 #bac1 #bca4    ,kelvin1    
,lord1 #bbi4    ,kempf1 ,p41 #aha4      
,kepler1 ,j41 #e1 #ce1 #acg4            
,kirchoff1 ,g4 ,r41 #fa1 #afi1 #agb4    
,kirkwood1 ,d41 #adj1 #bcj4    ,klein1  
,h4 ,j41 #gc4    ,klinkerfues1 ,e41     
#adb1 #bjb4    ,konkoly1 ,n41 #age4     
,kstner1 ,f41 #hh4                      
,l    ,lalande1 #bc1 #aeb4    ,lambert1 
,j4 ,h41 #cd4    ,lamont1 ,j41 #dd4     
,langley1 ,s4 ,p41 #gg4    ,laplace1 ,p4
 ,s41 #bj1 #cc1 #cd1 #gg1 #aji1 #adh1   
#aeb1 #aie1 #bbg1 #bbh1 #bbi4           
,lassell1 ,w41 #aab1 #aae1 #aag1 #abj4  

,latitude1 variation of1 #hh1 #hi4      
,leipzig ,observatory1 #agc4    ,leonid 
meteors1 #aci1 #adj1 #adb4    ,leonis   
771 #ahc4    ,lescarbault1 #hj4    ,le  
,verrier1 ,u4 ,j4 ,j41 #fa1 #hj1 #ha1   
#aah1 #aai1 #abj1 #adb1 #afd4    ,leyden
 ,observatory1 #ia4    ,libr 771 #ahj4  
,lick ,observatory1 #ic1 #ajg1 #aff1    
#afh1 #aia1 #bac4    ,light1 extinction 
of1 #dj1 #bae1 #baf1 #bbd1 #bbe4        
,lindsay1 ,lord1 #aeg4    ,linn1 #ga1   
#gb4    ,lockyer1 ,sir ,j4 ,n41 #eb1    
#ec1 #ed1 #ee1 #eh1 #adi1 #agd1 #aia1   
#aic1 #aie1            #bjh1 #bji1 #bca1
 #bcb4    ,lockyer1 ,w4 ,j4 ,s41 #baj4  
,loewy1 ,m41 #ge4    ,lohrmann1 ,w4 ,g41
 #fh1 #ga4    ,lohse1 ,w4 ,o41 #hh1     
#aje4    ,loomis1 #ahh4    ,lowell1 ,p41
 #hc1 #hd1 #hf1 #hg1 #ia1 #ib1 #ic1 #id1
 #abb1 #bcf1 #bcg4    ,lowell           
,observatory1 #ib1 #id1 #ajf1 #aad4     
,lund ,observatory1 #ei4    ,lupus1     
#bba4    ,luther1 ,r41 #ajj4    ,lyra1  
#bba4    ,lyra 771 #agh1 #ahb1 #ahe4    
,lyrid meteors1 #abb4                   

,m    ,maclaurin1 ,c41 #i4    ,maclear1 
,sir ,t41 #aee4    ,mdler1 ,j4 ,h41 #bg1
 #fh1 #fi1 #ga1 #if1 #ajd1 #bjb1 #bjc1  
#baf1 #bag1 #bah4    ,magellanic clouds1
 #bai4    ,magnetism1 #dd1 #fj4         
,mars1 #ah1 #ai1 #ij-ig1 #aja1 #add1    
#bcf4    ,maunder1 ,e4 ,w41 #ei1 #fj1   
#id1 #ie1 #acd1 #ade1 #aff1 #bbd4       
,mascari1 ,a41 #hf4    ,mayer1 ,c41     
#afd4    ,mayer1 ,j4 ,r41 #bbi4         
,mazapil meteorite1 #adi4    ,mchain1   
#abg4    ,mee1 ,a41 #fh4    ,melloni1   
#gf4    ,mercury1 #ah1 #hj1 #ha-hd1 #ig1
 #bcf4    ,messier1 ,c41 #cj4           
,meteorites1 #adg1 #adh1 #adi1 #bbi1    
#bca4    #8,meteoritic ,hypothesis1'    
#bca1 #bcb4    ,meteors1 #ach-adi4      
,meudon ,observatory1 #ei4    ,milan    
,observatory1 #hb1 #bjb1 #bbd4    ,milky
 ,way4 ,see ,galaxy4    ,miller1 ,w4    
,a41 #ej1 #agb4    ,mira ,ceti1 #aa1    
#ahb1 #ahf1 #ahg4    ,mitchel1 ,o4 ,m41 
#ca4    ,mizar 7 ,urs ,majoris71 #bjd4  
,mller1 ,a41 #abi4    ,moon1 the1 #aj1  
#bd1 #fe-gi1 #ij1 #ie1 #adh1 #bbh4      

,moscow ,observatory1 #acb4    ,mouchez1
 ,a41 #afa4    ,mller1 ,g41 #age1 #aha4 
,munich ,observatory1 #dd1 #bbd4        
,n    ,napoleon1 #fg1 #abg4    ,nasmyth1
 ,j41 #gc1 #ajc4    ,nebul1 #cj1 #ca1   
#bjg-bac1 #bbh4    ,nebular ,hypothesis1
 #cc1 #aie1 #bbg1 #bbh1 #bbi1 #bcj1     
#bcc4    ,neison 7,nevill71 ,e41 #gc4   
,neisten1 #hf1 #aje4    ,neptune1 #abj1 
#aba1 #ace1 #bbi1 #bcj4    ,newall1 ,h4 
,f41 #bje4    ,newcomb1 ,s41 #bg1 #fd1  
#gh1 #hi1 #id1 #afb1 #afh1 #bbj1 #bbb1  
#bbc1 #bbd1            #bcb4    ,newton1
 ,h4 ,a41 #adj1 #ada4    ,newton1 ,sir  
,i41 #b1 #ag1 #bi1 #gg4    ,nichol1 ,j4 
,p41 #ca1 #bjg4    ,nordvig1 ,l41 #aib4 
,o    ,olbers1 ,h4 ,w4 ,m41 #ai1 #bj1   
#fi1 #ih1 #ii1 #abc1 #abd1 #abe1 #abf1  
#abg1            #abi1 #acj1 #aci1 #adh1
 #aeb1 #aec4    ,olbers' comet1 #abe4   
,olmsted1 ,d41 #ach1 #bjg4    ,ophiuchi 
771 #ahc4    ,orion1 #bba4    ,orion    
nebula1 #aj1 #cc1 #bjg1 #bjh1 #bji1     
#bac4    ,orion stars1 #agd1 #aic1 #bji1
 #bcb4    ,orionis 771 #bji4    ,orionis

 771 #bji4    ,orionis 771 #bji4        
,orionis 7,u71 #aha1 #ahb1 #ahf1 #ahg4  
,p    ,palisa1 ,j41 #ajj4    ,pallas1   
#ai1 #ii1 #aja4    ,parallax1 solar1    
#fa1 #fb1 #fc1 #aja4    ,parallax1      
stellar1 #aej-aeh1 #aij4    ,paris      
,congresses1 #afa4    ,paris            
,observatory1 #gh1 #aah1 #aga4          
,perrine1 ,c4 ,d41 #ha1 #ajh1 #aid4     
,perrine's comet1 #acf4    ,perrotin1   
,h41 #hf1 #ia1 #ajj1 #aad4    ,peck1    
,w41 #afb4    ,persei 7,nova71 #aib1    
#aic1 #aid1 #aie4    ,perseid meteors1  
#abb1 #ada4    ,perseus1 #aib1 #bba4    
,peters1 ,c4 ,h4 ,f41 #ajj4    ,peters1 
,c4 ,a4 ,f41 #adb1 #aec1 #aee1 #bjb4    
,photography1 astronomical1 #ed1 #ef1   
#eg1 #ei1 #ge1 #ha1 #id1 #ajh1 #aac1    
#acf1 #aeh1 #afj1 #afa1 #agb1 #age1     
#aib1 #aic1 #aid1 #bjc1 #bjh1           
#bji1 #baj1 #baa1 #bab4    ,photometry1 
#agf1 #agg4    ,piazzi1 ,g41 #ai1 #bj1  
#ih1 #aej4    ,pickering1 ,e4 ,c41 #agd1
 #age1 #agf1 #agg1 #aha1 #ahb1 #ahc1    
#ahe1 #aic1            #aid1 #bjc1 #bjd1

 #bbj1 #bba4    ,pickering1 ,w4 ,h41    
#ge1 #gf1 #ha1 #ia1 #ib1 #ic1 #ajg1     
#aac1 #bji4    ,plana1 ,g41 #gh1 #gi4   
,pleiades1 #abd1 #baj1 #bag4    ,pogson1
 ,n4 ,r41 #adb1 #ahj4    ,pole ,star1   
#bje4    ,pollux1 #afe1 #agj4    ,pons1 
,j4 ,l41 #abg4    ,pontcoulant1 #gi4    
,potsdam ,observatory1 #df1 #agc1 #agf4 
,pritchard1 ,c41 #aeh1 #agg4            
,proctor1 ,r4 ,a41 #d1 #bj1 #ch1 #da1   
#ij1 #ia1 #ajd1 #adh1 #afc1 #afd1 #bah1 
#bai1 #bbj1 #bca4    ,procyon 7 ,canis  
,minoris71 #aea1 #bjc4    ,prominences1 
solar1 #eb1 #ec1 #ee1 #fd4    ,puiseux1 
,p41 #ge4    ,pulkowa ,observatory1     
#bjj4                                   
,q    ,quetelet1 ,a41 #aci4             
,r    ,radiant points1 meteoric1 #aci1  
#add1 #ade1 #adf4    ,ranyard1 ,a4 ,c41 
#ajf1 #adf4    ,red spot on ,jupiter1   
#aje1 #ajf4    ,regulus 7 ,leonis71     
#afd1 #afe4    ,relative parallax1 #aeg4
    ,rseau1 ,photospherique1 #ei4       
,resisting medium1 #abh4    ,respighi1  
,l41 #ee4    ,reversing layer1 #ef1 #eg4

    ,ricco1 ,a41 #hg1 #aje4    ,rigel 7 
,orionis71 #afe1 #bji4    ,ritchey1 ,g41
 #aid4    ,roberts1 ,a4 ,w41 #aha4      
,roberts1 ,i41 #bji1 #baj4    ,roche1   
,e41 #aji4    ,roman ,college           
,observatory1 #he4    ,rosse1 third     
,earl of1 #ada1 #aef1 #bjg1 #bjh1 #bah4 
,rosse1 fourth ,earl of1 #gg4           
,rotation of the ,sun1 #eh1 #ei2        
of the planets1 #hb1 #hc1 #hd1 #he1 #hf1
 #hg1 #ajd1 #aaa1 #aab4    ,rowland1 ,h4
 ,a41 #eb4    ,rutherfurd1 ,l4 ,m41 #ge1
 #afi4                                  
,s    ,sabine1 ,sir ,e41 #dd4           
,safford1 ,t4 ,h41 #bjb4    ,santini1   
,g41 #aei4    ,savary1 ,f41 #cj1 #aii4  
,satellites1 #if1 #ajg1 #ajh1 #aab1     
#aac1 #aae1 #abj1 #aba1 #bcf4           
,saturn1 #bj1 #ba1 #bb1 #ig1 #ajc1      
#ajh-aac1 #aba1 #ace4    ,schaeberle1   
,j4 ,m41 #ic1 #ajg1 #aia1 #bjc4         
,scheiner1 ,c41 #dd4    ,scheiner1 ,j41 
#aff1 #agd1 #agf4    ,schiaparelli1 ,g4 
,v41 #hb1 #hc1 #hd1 #he1 #hf1 #hg1 #ia1 
#ib1 #aad1 #ada1            #adc1 #adi1 

#bja1 #bbj1 #bbd1 #bca1 #bce4           
,schjellerup1 ,h41 #ahj4    ,schmidt1   
,j4 ,f4 ,j41 #fi1 #gj1 #ga1 #gb1 #gc1   
#ajd1 #agi1 #ahj1 #ahi4    ,schnfeld1   
,e41 #afj1 #agi1 #ahj1 #ahh1 #ahi4      
,schrter1 ,j4 ,h41 #af1 #fe1 #ff1 #fg1  
#fh1 #fi1 #gj1 #gd1 #ha1 #hb1 #hd1 #he1 
#hf1 #hg1 #ig1 #ii1 #aec4    ,schwabe1  
,s4 ,h41 #ah1 #dc1 #dd1 #df1 #ee4       
,schwassman1 ,a41 #ajj4    ,secchi1 ,a41
 #eb1 #ed1 #ee1 #fj1 #gb1 #ij1 #aad1    
#ada1 #agj1 #aga1 #agc4    ,secchi's    
types of stellar spectra1 #agj1 #aga1   
#agc1 #agd1 #age1 #ahi1            #bcb4
    ,see1 ,t4 ,j4 ,j41 #bja1 #bjb1 #bcf4
    ,seeliger1 ,h41 #aaj1 #aie1 #aif1   
#bjb1 #bjf1 #bbd1 #bbe4    ,serviss1 ,g4
 ,p41 #aeh4    ,sirius 7 ,canis         
,majoris71 #aea1 #agj1 #agc1 #ahh1 #bjb1
 #bbe4    ,slipher1 ,v4 ,m41 #ajf1 #aad1
 #bjd4    ,sime1 ,j41 #bg4    ,sola1 ,j4
 ,c41 #aab4    ,solar cluster1 #bba1    
#bbb4    ,solar system1 motion of1 #bf1 
#bg1 #afg1 #afh4    ,south1 ,sir ,j41   
#aih4    ,spectroscopic binaries1 #bjc1 

#bjd1 #bje4    ,spencer1 ,h41 #bah4     
,spica 7 ,virginis71 #bjd4    ,sprer1   
,f4 ,w4 ,g41 #de1 #df1 #ed1 #ei4        
,star-catalogues1 #aei1 #afj1 #afa1     
#afb4    ,star-clusters1 #cj1 #ca1 #cb1 
#bjf1 #baj4    ,star-drift1 #afd4       
,star-gauging1 #cf1 #dj1 #da1 #bbd4     
,stars1 distance of1 #aej-aeh4          
,stars1 distribution of1 #ce1 #ci1 #dj1 
#aih-bad4    ,stars1 double1 #bh1 #bi1  
#cj1 #aig-bjf4    ,stars1 gaseous1 #aga1
 #agd4    ,stars1 proper motion of1     
#afb1 #afc1 #afd1 #afe4    ,stars1      
radial motion of1 #afe1 #aff4    ,stars1
 temporary1 #aef1 #ahb1 #ahh-aif4       
,stars1 triple and multiple1 #bjf4      
,stars1 variable1 #agg-ahh4    ,stellar 
spectra1 #afi-agf1 #ahg1 #ahi1 #aij1    
#aia1 #aic1 #aid4    ,stellar universe1 
#ce-db1 #bad1 #bae-bbf4                 
,stereo-comparator1 #ajj1 #aja4         
,stokes1 ,sir ,g41 #ej4    ,stone1 ,e4  
,j41 #aeg1 #afj4    ,stroobant1 ,p41    
#hh4    ,struve1 ,f4 ,g4 ,w41 #c1 #cg1  
#ch1 #dj1 #db1 #abh1 #aea1 #aec1 #bjj1  

#bad1 #bae1            #baf1 #bah4      
,struve1 ,h41 #bja4    ,struve1 ,l41    
#bg1 #afc1 #afg4    ,struve1 ,o4 ,w41   
#bg1 #aaj1 #aae1 #abj1 #aec1 #aef1 #afc1
 #bjj1 #bja4    ,stumpe1 ,o41 #afg4     
,sun1 #ae1 #af1 #ag1 #dj1 #dc-fd1 #fe1  
#hj1 #ha1 #aje1 #abe1 #abh1 #agj1 #bbb1 
#bbh1 #bbi1 #bcj1 #bcg4    ,swift1 ,l41 
#ha4    ,swift's comet1 #acf4           
,t    ,tacchini1 ,p41 #ee1 #hf1 #hg4    
,taurus1 #bag1 #bba4    ,tempel1 ,e41   
#baj4    ,tennyson1 #if4    ,tidal      
friction1 #gi1 #hg1 #bcc1 #bcd1 #bce1   
#bcf4    ,tisserand1 ,f4 ,f41 #adf4     
,todd1 ,d4 ,p41 #abb4                   
,trans-,neptunian planet1 #aba1 #abb4   
,trouvelot1 ,e41 #hf1 #hg4              
,tschermak1 #adh4    ,tulse ,hill       
,observatory1 #aga4    ,turner1 ,h4 ,h41
 #aid1 #bbd4    ,twining1 ,a4 ,c41 #aci4
                                        
,u    ,upsala ,observatory1 #ei4        
,uranometria ,argentina1 #afj4          
,uranus1 #aa1 #bj1 #bb1 #bc1 #ig1 #aac1 
#aad1 #aae1 #aah1 #aba1 #ace1 #ada1     

#bcj4    ,ursa ,major1 #afb1 #afd4      
,urs ,majoris 771 #ahb4    ,urs ,majoris
 771 #aii4                              
,v    ,venus1 #ah1 #hd-hh1 #ig1 #bce1   
#bcf4    ,venus1 transits of1 #fa1 #fb1 
#hg4    ,vega 7 ,lyr71 #aea1 #afe1 #agj1
 #agb1 #agc4    ,very1 ,f4 ,w41 #gg4    
,vesta1 #ai1 #ii1 #aja1 #ajb4    ,vogel1
 ,h4 ,c41 #hd1 #hh1 #ie1 #ajb1 #ajf1    
#aad1 #aca1 #adh1 #aff1 #agc1 #agd1     
#age1 #ahc1 #ahd1 #ahe1 #aij1 #aia1     
#aic1 #aie1 #bjd1 #bji1 #bcb1           
#bcc1 #bcg4    ,vulcan1 #ha4            
,w    ,washington ,observatory1 #if1    
#bbc4    ,watson1 ,j4 ,c41 #ha1 #ajj4   
,webb1 ,t4 ,w41 #gb1 #gc1 #ajd4         
,weinek1 ,l41 #ge4    ,weiss1 ,e41 #adb4
    ,well's comet1 #acd4    ,whewell1   
,w41 #bah4    ,williams1 ,a4 ,s41 #aaj1 
#aic4    ,wilson1 ,a41 #af4    ,winlock1
 ,j41 #agg4    ,winnecke1 ,f4 ,a4 ,t41  
#aca4    ,witt1 ,k4 ,g41 #aja4    ,wolf1
 ,max1 #ajj1 #aha1 #aia1 #aid1 #baa4    
,wolf1 ,r41 #dd1 #de1 #ahh4    ,wolf and
 ,rayet1 #aga4    ,wolf-,rayet stars1   

#aga1 #agd4    ,wollaston1 ,w4 ,h41 #dh4
    ,wright1 ,t41 #cd1 #aaj4            
,y    ,yale ,observatory1 #aeg4         
,yerkes ,observatory1 #ee1 #aaa1 #bjb4  
,young1 ,c4 ,a41 #ed1 #ef1 #eg1 #eh1    
#fj1 #hg1 #aad1 #aij4                   
,z    ,zach1 ,f4 ,x41 #ig1 #ih1 #aeb4   
,zantedeschi1 #gg4    ,zenger1 #he1 #hh4
    ,zllner1 ,j4 ,c4 ,f41 #ed1 #eh1 #fj1
 #hd1 #ajc1 #acb1 #bcb4                 
,,corrigenda4      ,p4  #cj1 l4  #e1 for
 8objects0 read 8orbits40    ,p4  #cf1  
l4 #ac1 for 8unable0 read 8able40    ,p4
  #fa1 l4 #ag1 for 8#h4cga0 read        
8#h4ega40    ,p4  #fc1 l4 #ba1 for      
8bases0 read 8gases40    ,p4 #ajj1 l4   
#af1 for 8,schwussmann0 read            
8,schwassmann40    ,p4 #afg1 l4 #bh1 for
 8,strumpe0 read 8,stumpe40    ,p4 #ahd1
 l4 #aa1 for 8star-variables0 read      
8variable stars40    ,p4 #aii1 l4 #bc1  
for 8#bajb0 read 8#abjb40               
,,the ,,end4                            
,,printed ,,by ,,william ,,blackwood    
,,and ,,sons4                           

,transcriber's ,notes      --,silently  
corrected a few typos1 and incorporated 
the corrigenda into    the text4        
--,retained publication information from
 the printed edition3 this e,book    is 
public-domain in the country of         
publication4    --,in the text versions 
only1 text in italics is delimited by   
underscores4