,illustration3 ,fig4 #a4 ,the           
,constellation of ,orion 7,hubble74     
,photographed with a small camera lens  
of #a inch aperture and #e inches focal 
length4 ,the three bright stars in the  
centre of the picture form the belt of  
,orion4 ,just below1 in the sword       
handle1 is an irregular white patch     
about one-eighth of an inch in diameter4
 ,this is a small-scale image of the    
great nebula in ,orion1 shown on a      
larger scale in ,fig4 #b4     ,,the     
,,new ,,heavens   ,,by  ,,george        
,,ellery ,,hale  ,,director ,,of ,,the  
,,mount ,,wilson ,,observatory ,,of     
,,the ,,carnegie ,,institution ,,of     
,,washington  ,,with ,,numerous         
,,illustrations   ,,new ,,york          
,,charles ,,scribner',s ,,sons  #aibb   
,,to ,,my ,,wife     ,,preface          
,fourteen years ago1 in a book entitled 
,the ,study of ,stellar ,evolution      
7,university of ,chicago ,press1 #aijh71
 ,i attempted to give in untechnical    
language an account of some modern      

methods of astrophysical research4 ,this
 book is now out of print1 and the rapid
 progress of science has left it        
completely out of date4 ,as ,i have     
found no opportunity to prepare a new   
edition1 or to write another book of    
similar purpose1 ,i have adopted the    
simpler expedient of contributing       
occasional articles on recent           
developments to ,scribner's ,magazine1  
three of which are included in the      
present volume4  ,i am chiefly indebted1
 for the illustrations1 to the ,mount   
,wilson ,observatory and the present and
 former members of its staff whose names
 appear in the captions4 ,special thanks
 are due to ,mr4 ,ferdinand ,ellerman1  
who made all of the photographs of the  
observatory buildings and instruments1  
and prepared all material for           
reproduction4 ,the cut of the original  
,cavendish apparatus is copied from the 
,philosophical ,transactions for #agih  
with the kind permission of the ,royal  
,society1 and ,i am also indebted to the

 ,royal ,society and to ,professor      
,fowler and ,father ,cortie for the     
privilege of reproducing from the       
,proceedings two illustrations of their 
spectroscopic results4  ,g4 ,e4 ,h4     
,january1 #aibb4     ,,contents         
,,chapter     ,i4  ,,the ,,new ,,heavens
    ,,ii4  ,,giant ,,stars   ,,iii4     
,,cosmic ,,crucibles    ,,illustrations 
,,fig4   #a4 ,the ,constellation of     
,orion 7,hubble7   #b4 ,the ,great      
,nebula in ,orion 7,pease7   #c4 ,model 
by ,ellerman of summit of ,mount        
,wilson1 showing the observatory        
buildings among the trees and bushes    
#d4 ,the #ajj-;inch ,hooker telescope   
#e4 ,erecting the polar axis of the     
#ajj-;inch telescope   #f4 ,lowest      
section of tube of #ajj-;inch telescope1
 ready to leave ,pasadena      for      
,mount ,wilson   #g4 ,section of a steel
 girder for dome covering the #ajj-;inch
 telescope1      on its way up ,mount   
,wilson   #h4 ,erecting the steel       
building and revolving dome that cover  

the ,hooker      telescope   #i4        
,building and revolving dome1 #ajj feet 
in diameter1 covering the               
#ajj-;inch ,hooker telescope  #aj4      
,one-hundred-inch mirror1 just silvered1
 rising out of the      silvering-room  
in pier before attachment to lower end  
of telescope      tube4 7,seen above7   
#aa4 ,the driving-clock and worm-gear   
that cause the #ajj-;inch ,hooker       
telescope to follow the stars  #ab4     
,large irregular nebula and star cluster
 in ,sagittarius 7,duncan7  #ac4 ,faint 
spiral nebula in the constellation of   
the ,hunting ,dogs 7,pease7  #ad4       
,spiral nebula in ,andromeda1 seen edge 
on 7,ritchey7  #ae4 ,photograph of the  
moon made on ,september #ae1 #aiai1 with
 the #ajj-;inch      ,hooker telescope  
7,pease7  #af4 ,photograph of the moon  
made on ,september #ae1 #aiai1 with the 
#ajj-;inch      ,hooker telescope       
7,pease7  #ag4 ,hubble's ,variable      
,nebula4 ,one of the few nebul known to 
vary in      brightness and form  #ah4  

,ring ,nebula in ,lyra1 photographed    
with the #fj-;inch 7,ritchey7 and       
#ajj-;inch 7,duncan7 telescopes  #ai4   
,gaseous prominence at the sun's limb1  
#adj1jjj miles high 7,ellerman7  #bj4   
,the sun1 #hfe1jjj miles in diameter1   
from a direct photograph showing        
many sun-spots 7,whitney7  #ba4 ,great  
sun-spot group1 ,august #h1 #aiag       
7,whitney7  #bb4 ,photograph of the     
hydrogen atmosphere of the sun          
7,ellerman7  #bc4 ,diagram showing      
outline of the #ajj-;inch ,hooker       
telescope1 and path of      the two     
pencils of light from a star when under 
observation with the      #bj-;foot     
,michelson interferometer  #bd4         
,twenty-foot ,michelson interferometer  
for measuring star diameters1           
attached to upper end of the skeleton   
tube of the #ajj-;inch ,hooker          
telescope  #be4 ,the giant ,betelgeuse  
7within the circle71 familiar as the    
conspicuous      red star in the right  
shoulder of ,orion 7,hubble7  #bf4      

,arcturus 7within the white circle71    
known to the ,arabs as the ,lance       
,bearer1 and to the ,chinese as the     
,great ,horn or the ,palace of the      
,emperors 7,hubble7  #bg4 ,the giant    
star ,antares 7within the white circle71
 notable for its red      color in the  
constellation ,scorpio1 and named by the
 ,greeks ,a ,rival      of ,mars        
7,hubble7  #bh4 ,diameters of the ,sun1 
,arcturus1 ,betelgeuse1 and ,antares    
compared with      the orbit of ,mars   
#bi4 ,aldebaran1 the leader 7of the     
,pleiades71 was also known to the ,arabs
      as ,the ,eye of the ,bull1 ,the   
,heart of the ,bull1 and ,the ,great    
,camel 7,hubble7  #cj4 ,solar           
prominences1 photographed with the      
spectroheliograph without an            
eclipse 7,ellerman7  #ca4 ,the          
#aej-;foot tower telescope of the ,mount
 ,wilson ,observatory  #cb4 ,pasadena   
,laboratory of the ,mount ,wilson       
,observatory  #cc4 ,sun-spot vortex in  
the upper hydrogen atmosphere 7,benioff7

  #cd4 ,splitting of spectrum lines by a
 magnetic field 7,bacock7  #ce4         
,electric furnace in the ,pasadena      
,laboratory of the ,mount ,wilson       
,observatory  #cf4 ,titanium oxide in   
red stars  #cg4 ,titanium oxide in      
sun-spots  #ch4 ,the ,cavendish         
experiment  #ci4 ,the ,trifid ,nebula in
 ,sagittarius 7,ritchey7  #dj4 ,spiral  
nebula in ,ursa ,major 7,ritchey7  #da4 
,mount ,san ,antonio as seen from ,mount
 ,wilson     ,,chapter ,i  ,,the ,,new  
,,heavens  ,go out under the open sky1  
on a clear and moon-less night1 and try 
to count the stars4 ,if your station    
lies well beyond the glare of cities1   
which is often strong enough to conceal 
all but the brighter objects1 you will  
find the task a difficult one4 ,ranging 
through the six magnitudes of the ,greek
 astronomers1 from the brilliant ,sirius
 to the faintest perceptible points of  
light1 the stars are scattered in great 
profusion over the celestial vault4     
,their number seems limitless1 yet      

actual count will show that the eye has 
been deceived4 ,in a survey of the      
entire heavens1 from pole to pole1 it   
would not be possible to detect more    
than from six to seven thousand stars   
with the naked eye4 ,from a single      
viewpoint1 even with the keenest vision1
 only two or three thousand can be seen4
 ,so many of these are at the limit of  
visibility that ,ptolemy's ,almagest1 a 
catalogue of all the stars whose places 
were measured with the simple           
instruments of the ,greek astronomers1  
contains only #a1jbb stars4  ,back of   
,ptolemy1 through the speculations of   
the ,greek philosophers1 the mysteries  
of the ,egyptian sun-god1 and the       
observations of the ancient ,chaldeans1 
the rich and varied traditions of       
astronomy stretch far away into a       
shadowy past4 ,all peoples1 in the first
 stirrings of their intellectual youth1 
drawn by the nightly splendor of the    
skies and the ceaseless motions of the  
planets1 have set up some system of the 

heavens1 in which the sense of wonder   
and the desire for knowledge were no    
less concerned than the practical       
necessities of life4 ,the measurement of
 time and the needs of navigation have  
always stimulated astronomical research1
 but the intellectual demand has been   
keen from the first4 ,hipparchus and the
 ,greek astronomers of the ,alexandrian 
school1 shaking off the vagaries of     
magic and divination1 placed astronomy  
on a scientific basis1 though the       
reaction of the ,middle ,ages caused    
even such a great astronomer as ,tycho  
,brahe himself to revert for a time to  
the practice of astrology4  ,,early     
,,instruments  ,the transparent sky of  
,egypt1 rarely obscured by clouds1      
greatly favored ,ptolemy's observations4
 ,here was prepared his great star      
catalogue1 based upon the earlier       
observations of ,hipparchus1 and        
destined to remain alone in its field   
for more than twelve centuries1 until   
,ulugh ,bey1 ,prince of ,samarcand1     

repeated the work of his ,greek         
predecessor4 ,throughout this period the
 stars were looked upon mainly as points
 of reference for the observation of    
planetary motions1 and the instruments  
of observation underwent little change4 
,the astrolabe1 which consists of a     
circle divided into degrees1 with a     
rotating diametral arm for sighting     
purposes1 embodies their essential      
principle4 ,in its simple form1 the     
astrolabe was suspended in a vertical   
plane1 and the stars were observed by   
bringing the sights on the movable      
diameter to bear upon them4 ,their      
altitude was then read off on the       
circle4 ,ultimately1 the circle of the  
astrolabe1 mounted with one of its      
diameters parallel to the earth's axis1 
became the armillary sphere1 the        
precursor of our modern equatorial      
telescope4 ,great stone quadrants fixed 
in the meridian were also employed from 
very early times4 ,out of such          
furnishings1 little modified by the     

lapse of centuries1 was provided the    
elaborate instrumental equipment of     
,uranibourg1 the great observatory built
 by ,tycho ,brahe on the ,danish island 
of ,huen in #aegf4 ,in this ,city of the
 ,heavens1 still dependent solely upon  
the unaided eye as a collector of       
starlight1 ,tycho made those invaluable 
observations that enabled ,kepler to    
deduce the true laws of planetary       
motion4 ,but after all these centuries  
the sidereal world embraced no objects1 
barring an occasional comet or temporary
 star1 that lay beyond the vision of the
 earliest astronomers4 ,the conceptions 
of the stellar universe1 except those   
that ignored the solid ground of        
observation1 were limited by the small  
aperture of the human eye4 ,but the dawn
 of another age was at hand4            
,illustration3 ,fig4 #b4 ,the ,great    
,nebula in ,orion 7,pease74             
,photographed with the #ajj-;inch       
telescope4 ,this short-exposure         
photograph shows only the bright central

 part of the nebula4 ,a longer exposure 
reveals a vast outlying region4  ,the   
dominance of the sun as the central body
 of the solar system1 recognized by     
,aristarchus of ,samos nearly three     
centuries before the ,christian era1 but
 subsequently denied under the authority
 of ,ptolemy and the teachings of the   
,church1 was reaffirmed by the ,polish  
monk ,copernicus in #aedc4 ,kepler's    
laws of the motions of the planets1     
showing them to revolve in ellipses     
instead of circles1 removed the last    
defect of the ,copernican system1 and   
left no room for its rejection4 ,but    
both the world and the ,church clung to 
tradition1 and some visible             
demonstration was urgently needed4 ,this
 was supplied by ,galileo through his   
invention of the telescope4             
,illustration3 ,fig4 #c4 ,model by      
,ellerman of summit of ,mount ,wilson1  
showing the observatory buildings among 
the trees and bushes4  ,the #fj-;foot   
tower on the extreme left1 which is at  

the edge of a precipitous caon #a1ejj   
feet deep1 is the vertical telescope of 
the ,smithsonian ,astrophysical         
,observatory4 ,above it are the         
,monastery and other buildings used as  
quarters by the astronomers of the      
,mount ,wilson ,observatory while at    
work on the mountain4 7,the offices1    
computing-rooms1 laboratories1 and shops
 are in ,pasadena47 ,following the      
ridge1 we come successively to the dome 
of the #aj-;inch photographic telescope1
 the power-house1 laboratory1 ,snow     
horizontal telescope1 #fj-;foot-tower   
telescope1 and #aej-;foot-tower         
telescope1 these last three used for the
 study of the sun4 ,the dome of the     
#fj-;inch reflecting telescope is just  
below the #aej-;foot tower1 while that  
of the #ajj-;inch telescope is farther  
to the right4 ,the altitude of ,mount   
,wilson is about #e1ijj feet4  ,the     
crystalline lens of the human eye1      
limited by the iris to a maximum opening
 about one-quarter of an inch in        

diameter1 was the only collector of     
starlight available to the ,greek and   
,arabian astronomers4 ,galileo's        
telescope1 which in #afaj suddenly      
pushed out the boundaries of the known  
stellar universe and brought many       
thousands of stars into range1 had a    
lens about #b-a_/d inches in diameter4  
,the area of this lens1 proportional to 
the square of its diameter1 was about   
eighty-one times that of the pupil of   
the eye4 ,this great increase in the    
amount of light collected should bring  
to view stars down to magnitude #aj4e1  
of which nearly half a million are known
 to exist4  ,it is not too much to say  
that ,galileo's telescope revolutionized
 human thought4 ,turned to the moon1 it 
revealed mountains1 plains1 and valleys1
 while the sun1 previously supposed     
immaculate in its perfection1 was seen  
to be blemished with dark spots changing
 from day to day4 ,jupiter1 shown to be 
accompanied by four encircling          
satellites1 afforded a picture in       

miniature of the solar system1 and      
strongly supported the ,copernican view 
of its organization1 which was          
conclusively demonstrated by ,galileo's 
discovery of the changing phases of     
,venus and the variation of its apparent
 diameter during its revolution about   
the sun4 ,galileo's proof of the        
,copernican theory marked the downfall  
of medivalism and established astronomy 
on a firm foundation4 ,but while his    
telescope multiplied a hundredfold the  
number of visible stars1 more than a    
century elapsed before the true         
possibilities of sidereal astronomy were
 perceived4  ,illustration3 ,fig4 #d4   
,the #ajj-;inch ,hooker telescope4      
,,structure ,,of ,,the ,,universe  ,sir 
,william ,herschel was the first        
astronomer to make a serious attack upon
 the problem of the structure of the    
stellar universe4 ,in his first memoir  
on the ,construction of the ,heavens1   
read before the ,royal ,society in      
#aghd1 he wrote as follows3  ,hitherto  

the sidereal heavens have1 not          
inadequately for the purpose designed1  
been represented by the concave surface 
of a sphere in the centre of which the  
eye of an observer might be supposed to 
be placed4444 ,in future we shall look  
upon those regions into which we may now
 penetrate by means of such large       
telescopes1 as a naturalist regards a   
rich extent of ground or chain of       
mountains containing strata variously   
inclined and directed as well as        
consisting of very different materials4 
,on turning his #ah-;inch reflecting    
telescope to a part of the ,milky ,way  
in ,orion1 he found its whitish         
appearance to be completely resolved    
into small stars1 not separately seen   
with his former telescopes4 ,the        
glorious multitude of stars of all      
possible sizes that presented themselves
 here to my view are truly astonishing2 
but as the dazzling brightness of       
glittering stars may easily mislead us  
so far as to estimate their number      

greater than it really is1 ,i endeavored
 to ascertain this point by counting    
many fields1 and computing from a mean  
of them1 what a certain given portion of
 the ,milky ,way might contain4 ,by this
 means1 applied not only to the ,milky  
,way but to all parts of the heavens1   
,herschel determined the approximate    
number and distribution of all the stars
 within reach of his instrument4  ,by   
comparing many hundred gauges or counts 
of stars visible in a field of about    
one-quarter of the area of the moon1    
,herschel found that the average number 
of stars increased toward the great     
circle which most nearly conforms with  
the course of the ,milky ,way4 ,ninety  
degrees from this plane1 at the pole of 
the ,milky ,way1 only four stars1 on the
 average1 were seen in the field of the 
telescope4 ,in approaching the ,milky   
,way this number increased slowly at    
first1 and then more and more rapidly1  
until it rose to an average of #abb     
stars per field4  ,illustration3 ,fig4  

#e4 ,erecting the polar axis of the     
#ajj-;inch telescope4  ,these           
observations were made in the northern  
hemisphere1 and subsequently ,sir ,john 
,herschel1 using his father's telescope 
at the ,cape of ,good ,hope1 found an   
almost exactly similar increase of      
apparent star density for the southern  
hemisphere4 ,according to his estimates1
 the total number of stars in both      
hemispheres that could be seen          
distinctly enough to be counted in this 
telescope would probably be about five  
and one-half millions4  ,the ,herschels 
concluded that the stars of our         
firmament1 instead of being scattered in
 all directions indifferently through   
space1 form a stratum of which the      
thickness is small1 in comparison with  
its length and breadth2 and in which the
 earth occupies a place somewhere about 
the middle of its thickness1 between the
 point where it subdivides into two     
principal lamin inclined at a small     
angle to each other4 ,this view does not

 differ essentially from our modern     
conception of the form of the ,galaxy2  
but as the ,herschels were unable to see
 stars fainter than the fifteenth       
magnitude1 it is evident that their     
conclusions apply only to a restricted  
region surrounding the solar system1 in 
the midst of the enormously extended    
sidereal universe which modern          
instruments have brought within our     
range4  ,,modern ,,methods  ,the        
remarkable progress of modern astronomy 
is mainly due to two great instrumental 
advances3 the rise and development of   
the photographic telescope1 and the     
application of the spectroscope to the  
study of celestial objects4 ,these new  
and powerful instruments1 supplemented  
by many accessories which have          
completely revolutionized observatory   
equipment1 have not only revealed a     
vastly greater number of stars and      
nebul3 they have also rendered feasible 
observations of a type formerly regarded
 as impossible4 ,the chemical analysis  

of a faint star is now so easy that it  
can be accomplished in a very short     
time--as quickly1 in fact1 as an equally
 complex substance can be analyzed in   
the laboratory4 ,the spectroscope also  
measures a star's velocity1 the pressure
 at different levels in its atmosphere1 
its approximate temperature1 and now1 by
 a new and ingenious method1 its        
distance from the earth4 ,it determines 
the velocity of rotation of the sun and 
of nebul1 the existence and periods of  
orbital revolution of binary stars too  
close to be separated by any telescope1 
the presence of magnetic fields in      
sunspots1 and the fact that the entire  
sun1 like the earth1 is a magnet4       
,illustration3 ,fig4 #f4 ,lowest section
 of tube of #ajj-;inch telescope1 ready 
to leave ,pasadena for ,mount ,wilson4  
,such new possibilities1 with many      
others resulting from the application of
 physical methods of the most diverse   
character1 have greatly enlarged the    
astronomer's outlook4 ,he may now attack

 two great problems3 7#a7 ,the structure
 of the universe and the motions of its 
constituent bodies1 and 7#b7 the        
evolution of the stars3 their nature1   
origin1 growth1 and decline4 ,these two 
problems are intimately related and must
 be studied as one499  ,footnote 993 ,a 
third great problem open to the         
astronomer1 the study of the            
constitution of matter1 is described in 
,chapter ,,iii4  ,if space permitted1 it
 would be interesting to survey the     
progress already accomplished by modern 
methods of astronomical research4       
,hundreds of millions of stars have been
 photographed1 and the boundaries of the
 stellar universe have been pushed far  
into space1 but have not been attained4 
,globular star clusters1 containing tens
 of thousands of stars1 are on so great 
a scale 7according to ,shapley7 that    
light1 travelling at the rate of        
#ahf1jjj miles per second1 may take #ejj
 years to cross one of them1 while the  
most distant of these objects may be    

more than #bjj1jjj light-years from the 
earth4 ,the spiral nebul1 more than a   
million in number1 are vast whirling    
masses in process of development1 but we
 are not yet certain whether they should
 be regarded as island universes or as  
subordinate to the stellar system which 
includes our minute group of sun and    
planets1 the great star clouds of the   
,milky ,way1 and the distant globular   
star clusters4  ,illustration3 ,fig4 #g4
 ,section of a steel girder for dome    
covering the #ajj-;inch telescope1 on   
its way up ,mount ,wilson4  ,these few  
particulars may give a slight conception
 of the scale of the known universe1 but
 a word must be added regarding some of 
its most striking phenomena4 ,the great 
majority of the stars whose motions have
 been determined belong to one or the   
other of two great star streams1 but the
 part played by these streams in the    
sidereal system as a whole is still     
obscure4 ,the stars have been grouped in
 classes1 presumably in the order of    

their evolutional development1 as they  
pass from the early state of gaseous    
masses1 of low density1 through the     
successive stages resulting from loss of
 heat by radiation and increased density
 due to shrinkage4 ,strangely enough1   
their velocities in space show a        
corresponding change1 increasing as they
 grow older or perhaps depending upon   
their mass4  ,it is impossible within   
these limits to do more than to give    
some indication of the scope of the new 
astronomy4 ,enough has been said1       
however1 to assist in appreciating the  
increased opportunity for investigation1
 and the nature of the heavy demands    
made upon the modern observatory4 ,but  
before passing on to describe one of the
 latest additions to the astronomer's   
instrumental equipment1 a word should be
 added regarding the chief classes of   
telescopes4  ,,refractors ,,and         
,,reflectors  ,astronomical telescopes  
are of two types3 refractors and        
reflectors4 ,a refracting telescope     

consists of an object-glass composed of 
two or more lenses1 mounted at the upper
 end of a tube1 which is pointed at the 
celestial object4 ,the light1 after     
passing through the lenses1 is brought  
to a focus at the lower end of the tube1
 where the image is examined visually   
with an eyepiece1 or photographed upon a
 sensitive plate4 ,the largest          
instruments of this type are the        
#cf-;inch ,lick telescope and the       
#dj-;inch refractor of the ,yerkes      
,observatory4  ,illustration3 ,fig4 #h4 
,erecting the steel building and        
revolving dome that cover the ,hooker   
telescope4  ,reflecting telescopes1     
which are particularly adapted for      
photographic work1 though also excellent
 for visual observations1 are very      
differently constructed4 ,no lens is    
used4 ,the telescope tube is usually    
built in skeleton form1 open at its     
upper end1 and with a large concave     
mirror supported at its base4 ,this     
mirror serves in place of a lens4 ,its  

upper surface is paraboloidal in shape1 
as a spherical surface will not unite in
 a sharp focus the rays coming from a   
distant object4 ,the light passes       
through no glass--a great advantage1    
especially for photography1 as the      
absorption in lenses cuts out much of   
the blue and violet light1 to which     
photographic plates are most sensitive4 
,the reflection occurs on the upper     
surface of the mirror1 which is covered 
with a coat of pure silver1 renewed     
several times a year and always kept    
highly burnished4 ,silvered glass is    
better than metals or other substances  
for telescope mirrors1 chiefly because  
of the perfection with which glass can  
be ground and polished1 and the ease of 
renewing its silvered surface when      
tarnished4  ,the great reflectors of    
,herschel and ,lord ,rosse1 which were  
provided with mirrors of speculum metal1
 were far inferior to much smaller      
telescopes of the present day4 ,with    
these instruments the star images were  

watched as they were carried through the
 field of view by the earth's rotation1 
or kept roughly in place by moving the  
telescope with ropes or chains4         
,photographic plates1 which reveal      
invisible stars and nebul when exposed  
for hours in modern instruments1 were   
not then available4 ,in any case they   
could not have been used1 in the absence
 of the perfect mechanism required to   
keep the star images accurately fixed in
 place upon the sensitive film4         
,illustration3 ,fig4 #i4 ,building and  
revolving dome1 #ajj feet in diameter1  
covering the #ajj-;inch ,hooker         
telescope4  ,photographed from the      
summit of the #aej-;foot-tower          
telescope4  ,it would be interesting to 
trace the long contest for supremacy    
between refracting and reflecting       
telescopes1 each of which1 at certain   
stages in its development1 appeared to  
be unrivalled4 ,in modern observatories 
both types are used1 each for the       
purpose for which it is best adapted4   

,for the photography of nebul and the   
study of the fainter stars1 the         
reflector has special advantages1       
illustrated by the work of such         
instruments as the ,crossley and ,mills 
reflectors of the ,lick ,observatory2   
the great #gb-;inch reflector1 recently 
brought into effective service at the   
,dominion ,observatory in ,canada2 and  
the #fj-;inch and #ajj-;inch reflectors 
of the ,mount ,wilson ,observatory4     
,the unaided eye1 with an available area
 of one-twentieth of a square inch1     
permits us to see stars of the sixth    
magnitude4 ,herschel's #ah-;inch        
reflector1 with an area #e1jjj times as 
great1 rendered visible stars of the    
fifteenth magnitude4 ,the #fj-;inch     
reflector1 with an area #eg1fjj times   
that of the eye1 reveals stars of the   
eighteenth magnitude1 while to reach    
stars of about the twentieth magnitude1 
photographic exposures of four or five  
hours suffice with this instrument4     
,every gain of a magnitude means a great

 gain in the number of stars rendered   
visible4 ,stars of the second magnitude 
are #c4d times as numerous as those of  
the first1 those of the eighth magnitude
 are three times as numerous as those of
 the seventh1 while the sixteenth       
magnitude stars are only #a4g as        
numerous as those of the fifteenth      
magnitude4 ,this steadily decreasing    
ratio is probably due to an actual      
thinning out of the stars toward the    
boundaries of the stellar universe1 as  
the most exhaustive tests have failed to
 give any evidence of absorption of     
light in its passage through space4 ,but
 in spite of this decrease1 the gain of 
a single additional magnitude may mean  
the addition of many millions of stars  
to the total of those already shown by  
the #fj-;inch reflector4 ,here is one of
 the chief sources of interest in the   
possibilities of a #ajj-;inch reflecting
 telescope4  #ajj-;,,inch ,,telescope   
,illustration3 ,fig4 #aj4               
,one-hundred-inch mirror1 just silvered1

 rising out of the silvering-room in    
pier before attachment to lower end of  
telescope tube4 7,seen above47  ,in     
#aijf the late ,john ,d4 ,hooker1 of    
,los ,angeles1 gave the ,carnegie       
,institution of ,washington a sum       
sufficient to construct a telescope     
mirror #ajj inches in diameter1 and thus
 large enough to collect #afj1jjj times 
the light received by the eye4 7,fig4   
#aj47 ,the casting and annealing of a   
suitable glass disk1 #aja inches in     
diameter and #ac inches thick1 weighing 
four and one-half tons1 was a most      
difficult operation1 finally            
accomplished by a great ,french glass   
company at their factory in the ,forest 
of ,st4 ,gobain4 ,a special optical     
laboratory was erected at the ,pasadena 
headquarters of the ,mount ,wilson      
,observatory1 and here the long task of 
grinding1 figuring1 and testing the     
mirror was successfully carried out by  
the observatory opticians4 ,this        
operation1 which is one of great        

delicacy1 required years for its        
completion4 ,meanwhile the building1    
dome1 and mounting for the telescope    
were designed by members of the         
observatory staff1 and the working      
drawings were prepared4 ,an opportune   
addition by ,mr4 ,carnegie to the       
endowment of the ,carnegie ,institution 
of ,washington1 of which the observatory
 is a branch1 permitted the necessary   
appropriations to be made for the       
completion and erection of the          
telescope4 ,though delayed by the war1  
during which the mechanical and optical 
facilities of the observatory shops were
 utilized for military and naval        
purposes1 the telescope is now in       
regular use on ,mount ,wilson4  ,the    
instrument is mounted on a massive pier 
of reinforced concrete1 #cc feet high   
and #eb feet in diameter at the top4 ,a 
solid wall extends south from this pier 
a distance of #ej feet1 on the west side
 of which a very powerful spectrograph1 
for photographing the spectra of the    

brightest stars1 will be mounted4       
,within the pier are a photographic dark
 room1 a room for silvering the large   
mirror 7which can be lowered into the   
pier71 and the clock-room1 where stands 
the powerful driving-clock1 with which  
the telescope is caused to follow the   
apparent motion of the stars4 7,fig4    
#aa47  ,illustration3 ,fig4 #aa4 ,the   
driving-clock and worm-gear that cause  
the #ajj-;inch ,hooker telescope to     
follow the stars4  ,the telescope       
mounting is of the ,english type1 in    
which the telescope tube is supported by
 the declination trunnions between the  
arms of the polar axis1 built in the    
form of a rectangular yoke carried by   
bearings on massive pedestals to the    
north and south4 ,these bearings must be
 aligned exactly parallel to the axis of
 the earth1 and must support the polar  
axis so freely that it can be rotated   
with perfect precision by the           
driving-clock1 which turns a worm-wheel 
#ag feet in diameter1 clamped to the    

lower end of the axis4 ,as this motion  
must be sufficiently uniform to         
counteract exactly the rotation of the  
earth on its axis1 and thus to maintain 
the star images accurately in position  
in the field of view1 the greatest care 
had to be taken in the construction of  
the driving-clock and in the spacing and
 cutting of the teeth in the large      
worm-wheel4 ,here1 as in the case of all
 of the more refined parts of the       
instrument1 the work was done by skilled
 machinists in the observatory shops in 
,pasadena or on ,mount ,wilson after the
 assembling of the telescope4 ,the      
massive sections of the instrument1 some
 of which weigh as much as ten tons     
each1 were constructed at ,quincy1      
,mass41 where machinery sufficiently    
large to build battleships was          
available4 ,they were then shipped to   
,california1 and transported to the     
summit of ,mount ,wilson over a road    
built for this purpose by the           
construction division of the            

observatory1 which also built the pier  
on which the telescope stands1 and      
erected the steel building and dome that
 cover it4  ,illustration3 ,fig4 #ab4   
,large irregular nebula and star cluster
 in ,sagittarius 7,duncan74             
,photographed with the #fj-;inch        
telescope4  ,illustration3 ,fig4 #ac4   
,faint spiral nebula in the             
constellation of the ,hunting ,dogs     
7,pease74  ,photographed with the       
#fj-;inch telescope4  ,the parts of the 
telescope which are moved by the        
driving-clock weigh about #ajj tons1 and
 it was necessary to provide means of   
reducing the great friction on the      
bearings of the polar axis4 ,to         
accomplish this1 large hollow steel     
cylinders1 floating in mercury held in  
cast-iron tanks1 were provided at the   
upper and lower ends of the polar axis4 
,almost the entire weight of the        
instrument is thus floated in mercury1  
and in this way the friction is so      
greatly reduced that the driving-clock  

moves the instrument with perfect ease  
and smoothness4  ,the #ajj-;inch mirror 
rests at the bottom of the telescope    
tube on a special support system1 so    
designed as to prevent any bending of   
the glass under its own weight4         
,electric motors1 forty in number1 are  
provided to move the telescope rapidly  
or slowly in right ascension 7east or   
west7 and in declination 7north or      
south71 for focussing the mirrors1 and  
for many other purposes4 ,they are also 
used for rotating the dome1 #ajj feet in
 diameter1 under which the telescope is 
mounted1 and for opening the shutter1   
#bj feet wide1 through which the        
observations are made4  ,a telescope of 
this kind can be used in several        
different ways4 ,the #ajj-;inch mirror  
has a focal length of about #db feet1   
and in one of the arrangements of the   
instrument1 the photographic plate is   
mounted at the centre of the telescope  
tube near its upper end1 where it       
receives directly the image formed by   

the large mirror4 ,in another           
arrangement1 a silvered glass mirror1   
with plane surface1 is supported near   
the upper end of the tube at an angle of
 #de1 so as to form the image at the    
side of the tube1 where the photographic
 plate can be placed4 ,in this case1 the
 observer stands on a platform1 which is
 moved up and down by electric motors in
 front of the opening in the dome       
through which the observations are made4
  ,illustration3 ,fig4 #ad4 ,spiral     
nebula in ,andromeda1 seen edge on      
7,ritchey74  ,photographed with the     
#fj-;inch telescope4  ,other            
arrangements of the telescope1 for which
 auxiliary convex mirrors carried near  
the upper end of the tube are required1 
permit the image to be photographed at  
the side of the tube near its lower end1
 either with or without a spectrograph2 
or with a very powerful spectrograph    
mounted within a constant-temperature   
chamber south of the telescope pier4 ,in
 this last case1 the light of a star is 

so reflected by auxiliary mirrors that  
it passes down through a hole in the    
south end of the polar axis and brings  
the star to a focus on the slit of the  
fixed spectrograph4  ,,atmospheric      
,,limitations  ,the huge dimensions of  
such a powerful engine of research as   
the ,hooker telescope are not in        
themselves a source of satisfaction to  
the astronomer1 for they involve a      
decided increase in the labor of        
observation and entail very heavy       
expense1 justifiable only in case       
important results1 beyond the reach of  
other instruments1 can be secured4 ,the 
construction of a telescope of these    
dimensions was necessarily an           
experiment1 for it was by no means      
certain1 after the optical and          
mechanical difficulties had been        
overcome1 that even the favorable       
atmosphere of ,california would be      
sufficiently tranquil to permit sharply 
defined celestial images to be obtained 
with so large an aperture4 ,it is       

therefore important to learn what the   
telescope will actually accomplish under
 customary observing conditions4        
,fortunately we are able to measure the 
performance of the instrument with      
certainty4 ,close beside it on ,mount   
,wilson stands the #fj-;inch reflector1 
of similar type1 erected in #aijh4 ,the 
two telescopes can thus be rigorously   
compared under identical atmospheric    
conditions4  ,the large mirror of the   
#ajj-;inch telescope has an area about  
#b4h times that of the #fj-;inch1 and   
therefore receives nearly three times as
 much light from a star4 ,under         
atmospheric conditions perfect enough to
 allow all of this light to be          
concentrated in a point1 it should be   
capable of recording on a photographic  
plate1 with a given exposure1 stars     
about one magnitude fainter than the    
faintest stars within reach of the      
#fj-;inch4 ,the increased focal length1 
permitting such objects as the moon to  
be photographed on a larger scale1      

should also reveal smaller details of   
structure and render possible higher    
accuracy of measurement4 ,finally1 the  
greater theoretical resolving power of  
the larger aperture1 providing it can be
 utilized1 should permit the separation 
of the members of close double stars    
beyond the range of the smaller         
instrument4  ,,critical ,,tests  ,the   
many tests already made indicate that   
the advantages expected of the new      
telescope will be realized in practice4 
,the increased light-gathering power    
will mean the addition of many millions 
of stars to those already known4        
,spectroscopic observations now in      
regular progress have carried the range 
of these investigations far beyond the  
possibilities of the #fj-;inch          
telescope4 ,a great class of red stars1 
for example1 almost all the members of  
which were inaccessible to the          
#fj-;inch1 are now being made the       
subject of special study4 ,and in other 
fields of research equal advantages have

 been gained4  ,the increase in the     
scale of the images over those given by 
the #fj-;inch telescope is illustrated  
by two photographs of the ,ring ,nebula 
in ,lyra1 reproduced in ,fig4 #ah4 ,the 
,great ,nebula in ,orion1 photographed  
with the #ajj-;inch telescope with a    
comparatively short exposure1 sufficient
 to bring out the brighter regions1 is  
reproduced in ,fig4 #b4 ,it is          
interesting to compare this picture with
 the small-scale image of the same      
nebula shown in ,fig4 #a4               
,illustration3 ,fig4 #ae4 ,photograph of
 the moon made on ,september #ae1 #aiai1
 with the #ajj-;inch ,hooker telescope  
7,pease74  ,the ring-like formations are
 the so-called craters1 most of them far
 larger than anything similar on the    
earth4 ,that in the lower left corner   
with an isolated mountain in the centre 
is ,albategnius1 sixty-four miles in    
diameter4 ,peaks in the ring rise to a  
height of fifteen thousand feet above   
the central plain4 ,note the long sunset

 shadows cast by the mountains on the   
left4 ,the level region below on the    
right is an extensive plain1 the ,mare  
,nubium4  ,illustration3 ,fig4 #af4     
,photograph of the moon made on         
,september #ae1 #aiai1 with the         
#ajj-;inch ,hooker telescope 7,pease74  
,the mountains above and to the left are
 the lunar ,apennines2 those on the left
 just below the centre are the ,alps4   
,both ranges include peaks from fifteen 
thousand to twenty thousand feet in     
height4 ,in the upper right corner is   
,copernicus1 about fifty miles in       
diameter4 ,the largest of the           
conspicuous group of three just below   
the ,apennines is ,archimedes and at the
 lower end of the ,alps is ,plato4 ,note
 the long sunset shadows cast by the    
isolated peaks on the left4 ,the central
 portion of the picture is a vast plain1
 the ,mare ,imbrium4  ,the sharpness of 
the images given by the new telescope   
may be illustrated by some recent       
photographs of the moon1 obtained with  

an equivalent focal length of #acd feet4
 ,in ,fig4 #ae is shown a rugged region 
of the moon1 containing many ring-like  
mountains or craters4 ,fig4 #af shows   
the great arc of the lunar ,apennines   
7above7 and the ,alps 7below71 to the   
left of the broad plain of the ,mare    
,imbrium4 ,the starlike points along the
 moon's terminator1 which separates the 
dark area from the region upon which the
 sun 7on the right7 shines1 are the     
mountain peaks1 about to disappear at   
sunset4 ,the long shadows cast by the   
mountains just within the illuminated   
area are plainly seen4 ,some of the     
peaks of the lunar ,apennines attain a  
height of #bj1jjj feet4  ,in less       
powerful telescopes the stars at the    
centre of the great globular clusters   
are so closely crowded together that    
they cannot be studied separately with  
the spectrograph4 ,moreover1 most of    
them are much too faint for examination 
with this instrument4 ,at the #acd-;foot
 focus the #ajj-;inch telescope gives a 

large-scale image of such clusters1 and 
permits the spectra of stars as faint as
 the fifteenth magnitude to be          
separately photographed4  ,illustration3
 ,fig4 #ag4 ,hubble's ,variable ,nebula4
 ,one of the few nebul known to vary in 
brightness and form4  ,photographed with
 the #ajj-;inch telescope 7,hubble74    
,,close ,,double ,,stars  ,a remarkable 
use of the #ajj-;inch telescope1 which  
permits its full theoretical resolving  
power to be not merely attained but to  
be doubled1 has been made possible by   
the first application of ,michelson's   
interference method to the measurement  
of very close double stars4 ,when       
employing this1 the #ajj-;inch mirror is
 completely covered1 except for two     
slits4 ,beams of light from a star1     
entering by the slits1 unite at the     
focus of the telescope1 where the image 
is examined by an eyepiece magnifying   
about five thousand diameters4 ,across  
the enlarged star image a series of     
fine1 sharp fringes is seen1 even when  

the atmospheric conditions are poor4 ,if
 the star is single the fringes remain  
visible1 whatever the distance between  
the slits4 ,but in the case of a star   
like ,capella1 previously inferred to be
 double from the periodic displacement  
of the lines in its spectrum1 but with  
components too close together to be     
distinguished separately1 the fringes   
behave differently4 ,as the slits are   
moved apart a point is reached where the
 fringes completely disappear1 only to  
reappear as the separation is continued4
 ,this effect is obtained when the slits
 are at right angles to the line joining
 the two stars of the pair1 found by    
this method to be #j4jdah of a second of
 arc apart 7on ,december #cj1 #aiai74   
,subsequent measures1 of far greater    
precision than those obtainable by other
 methods in the case of easily separated
 double stars1 show the rapid orbital   
motion of the components of the system4 
,this device will be applied to other   
close binaries1 hitherto beyond the     

reach of measurement4  ,illustration3   
,fig4 #ah4 ,ring ,nebula in ,lyra1      
photographed with the #fj-;inch         
7,ritchey7 and #ajj-;inch 7,duncan7     
telescopes4  ,showing the increased     
scale of the images given by the larger 
instrument4  ,without entering into     
further details of the tests1 it is     
evident that the new telescope will     
afford boundless possibilities for the  
study of the stellar universe499 ,the   
structure and extent of the galactic    
system1 and the motions of the stars    
comprising it2 the distribution1        
distances1 and dimensions of the spiral 
nebul1 their motions1 rotation1 and mode
 of development2 the origin of the stars
 and the successive stages in their life
 history3 these are some of the great   
questions which the new telescope must  
help to answer4 ,in such an             
embarrassment of riches the chief       
difficulty is to withstand the          
temptation toward scattering of effort1 
and to form an observing programme      

directed toward the solution of crucial 
problems rather than the accumulation of
 vast stores of miscellaneous data4     
,this programme will be supplemented by 
an extensive study of the sun1 the only 
star near enough the earth to be        
examined in detail1 and by a series of  
laboratory investigations involving the 
experimental imitation of solar and     
stellar conditions1 thus aiding in the  
interpretation of celestial phenomena4  
,footnote 993 ,it is not adapted for    
work on the sun1 as the mirrors would be
 distorted by its heat4 ,three other    
telescopes1 especially designed for     
solar observations1 are in use on ,mount
 ,wilson4     ,,chapter ,,ii  ,,giant   
,,stars  ,our ancestral sun1 as pictured
 by ,laplace1 originally extended in a  
state of luminous vapor beyond the      
boundaries of the solar system4         
,rotating upon its axis1 it slowly      
contracted through loss of heat by      
radiation1 leaving behind it portions of
 its mass1 which condensed to form the  

planets4 ,still gaseous1 though now     
denser than water1 it continues to pour 
out the heat on which our existence     
depends1 as it shrinks imperceptibly    
toward its ultimate condition of a cold 
and darkened globe4  ,laplace's         
hypothesis has been subjected in recent 
years to much criticism1 and there is   
good reason to doubt whether his        
description of the mode of evolution of 
our solar system is correct in every    
particular4 ,all critics agree1 however1
 that the sun was once enormously larger
 than it now is1 and that the planets   
originally formed part of its distended 
mass4  ,even in its present diminished  
state1 the sun is huge beyond easy      
conception4 ,our own earth1 though so   
minute a fragment of the primeval sun1  
is nevertheless so large that some parts
 of its surface have not yet been       
explored4 ,seen beside the sun1 by an   
observer on one of the planets1 the     
earth would appear as an insignificant  
speck1 which could be swallowed with    

ease by the whirling vortex of a        
sun-spot4 ,if the sun were hollow1 with 
the earth at its centre1 the moon1      
though #bdj1jjj miles from us1 would    
have room and to spare in which to      
describe its orbit1 for the sun is      
#hfe1jjj miles in diameter1 so that its 
volume is more than a million times that
 of the earth4  ,illustration3 ,fig4    
#ai4 ,gaseous prominence at the sun's   
limb1 #adj1jjj miles high 7,ellerman74  
,photographed with the                  
spectroheliograph1 using the light      
emitted by glowing calcium vapor4 ,the  
comparative size of the earth is        
indicated by the white circle4  ,but    
what of the stars1 proved by the        
spectroscope to be self-luminous1       
intensely hot1 and formed of the same   
chemical elements that constitute the   
sun and the earth8 ,are they comparable 
in size with the sun8 ,do they occur in 
all stages of development1 from infancy 
to old age8 ,and if such stages can be  
detected1 do they afford indications of 

the gradual diminution in volume which  
,laplace imagined the sun to experience8
  ,illustration3 ,fig4 #bj4 ,the sun1   
#hfe1jjj miles in diameter1 from a      
direct photograph showing many sun-spots
 7,whitney7  ,the small black disk in   
the centre represents the comparative   
size of the earth1 while the circle     
surrounding it corresponds in diameter  
to the orbit of the moon4  ,,star       
,,images  ,prior to the application of  
the powerful new engine of research     
described in this article we have had no
 means of measuring the diameters of the
 stars4 ,we have measured their         
distances and their motions1 determined 
their chemical composition1 and obtained
 undeniable evidence of progressive     
development1 but even in the most       
powerful telescopes their images are so 
minute that they appear as points rather
 than as disks4 ,in fact1 the larger the
 telescope and the more perfect the     
atmospheric conditions at the observer's
 command1 the smaller do these images   

appear4 ,on the photographic plate1 it  
is true1 the stars are recorded as      
measurable disks1 but these are due to  
the spreading of the light from their   
bright point-like images1 and their     
diameters increase as the exposure time 
is prolonged4 ,from the images of the   
brighter stars rays of light project in 
straight lines1 but these also are      
instrumental phenomena1 due to          
diffraction of light by the steel bars  
that support the small mirror in the    
tube of reflecting telescopes4 ,in a    
word1 the stars are so remote that the  
largest and most perfect telescopes show
 them only as extremely minute          
needle-points of light1 without any     
trace of their true disks4              
,illustration3 ,fig4 #ba4 ,great        
sun-spot group1 ,august #h1 #aiag       
7,whitney74  ,the disk in the corner    
represents the comparative size of the  
earth4  ,how1 then1 may we hope to      
measure their diameters8 ,by using1 as  
the man of science must so often do1    

indirect means when the direct attack   
fails4 ,most of the remarkable progress 
of astronomy during the last            
quarter-century has resulted from the   
application of new and ingenious devices
 borrowed from the physicist4 ,these    
have multiplied to such a degree that   
some of our observatories are literally 
physical laboratories1 in which the sun 
and stars are examined by powerful      
spectroscopes and other optical         
instruments that have recently advanced 
our knowledge of physics by leaps and   
bounds4 ,in the present case we are     
indebted for our star-measuring device  
to the distinguished physicist          
,professor ,albert ,a4 ,michelson1 who  
has contributed a long array of novel   
apparatus and methods to physics and    
astronomy4  ,,the ,,interferometer  ,the
 instrument in question1 known as the   
interferometer1 had previously yielded a
 remarkable series of results when      
applied in its various forms to the     
solution of fundamental problems4 ,to   

mention only a few of those that have   
helped to establish ,michelson's fame1  
we may recall that our exact knowledge  
of the length of the international metre
 at ,sevres1 the world's standard of    
measurement1 was obtained by him with an
 interferometer in terms of the         
invariable length of light-waves4 ,a    
different form of interferometer has    
more recently enabled him to measure the
 minute tides within the solid body of  
the earth--not the great tides of the   
ocean1 but the slight deformations of   
the earth's body1 which is as rigid as  
steel1 that are caused by the varying   
attractions of the sun and moon4        
,finally1 to mention only one more case1
 it was the ,michelson-,morley          
experiment1 made years ago with still   
another form of interferometer1 that    
yielded the basic idea from which the   
theory of relativity was developed by   
,lorentz and ,einstein4  ,illustration3 
,fig4 #bb4 ,photograph of the hydrogen  
atmosphere of the sun 7,ellerman74      

,made with the spectroheliograph1       
showing the immense vortices1 or        
whirling storms like tornadoes1 that    
centre in sun-spots4 ,the comparative   
size of the earth is shown by the white 
circle traced on the largest sun-spot4  
,the history of the method of measuring 
star diameters is a very curious one1   
showing how the most promising          
opportunities for scientific progress   
may lie unused for decades4 ,the        
fundamental principle of the device was 
first suggested by the great ,french    
physicist ,fizeau in #ahfh4 ,in #ahgd   
the theory was developed by the ,french 
astronomer ,stphan1 who observed        
interference fringes given by a large   
number of stars1 and rightly concluded  
that their angular diameters must be    
much smaller than #j4aeh of a second of 
arc1 the smallest measurable with his   
instrument4 ,in #ahij ,michelson1       
unaware of the earlier work1 published  
in the ,philosophical ,magazine a       
complete description of an              

interferometer capable of determining   
with surprising accuracy the distance   
between the components of double stars  
so close together that no telescope can 
separate them4 ,he also showed how the  
same principle could be applied to the  
measurement of star diameters if a      
sufficiently large interferometer could 
be built for this purpose1 and developed
 the theory much more completely than   
,stphan had done4 ,a year later he      
measured the diameters of ,jupiter's    
satellites by this means at the ,lick   
,observatory4 ,but nearly thirty years  
elapsed before the next step was taken4 
,two causes have doubtless contributed  
to this delay4 ,both theory and         
experiment have demonstrated the extreme
 sensitiveness of the interference      
fringes1 on the observation of which the
 method depends1 and it was generally   
supposed by astronomers that            
disturbances in the earth's atmosphere  
would prevent them from being clearly   
seen with large telescopes4             

,furthermore1 a very large              
interferometer1 too large to be carried 
by any existing telescope1 was required 
for the star-diameter work1 though close
 double stars could have been easily    
studied by this device with several of  
the large telescopes of the early       
nineties4 ,but whatever the reasons1 a  
powerful method of research lay unused4 
,the approaching completion of the      
#ajj-;inch telescope of the ,mount      
,wilson ,observatory led me to suggest  
to ,professor ,michelson1 before the    
,united ,states entered the war1 that   
the method be thoroughly tested under   
the favorable atmospheric conditions of 
,southern ,california4 ,he was at that  
time at work on a special form of       
interferometer1 designed to determine   
whether atmospheric disturbances could  
be disregarded in planning large-scale  
experiments4 ,but the war intervened1   
and all of our efforts were concentrated
 for two years on the solution of war   
problems499 ,in #aiai1 as soon as the   

#ajj-;inch telescope had been completed 
and tested1 the work was resumed on     
,mount ,wilson4  ,footnote 993          
,professor ,michelson's most important  
contribution during the war period was a
 new and very efficient form of         
range-finder1 adopted for use by the ,u4
 ,s4 ,navy4  ,a ,,laboratory            
,,experiment  ,the principle of the     
method can be most readily seen by the  
aid of an experiment which any one can  
easily perform for himself with simple  
apparatus4 ,make a narrow slit1 a few   
thousandths of an inch in width1 in a   
sheet of black paper1 and support it    
vertically before a brilliant source of 
light4 ,observe this from a distance of 
#dj or #ej feet with a small telescope  
magnifying about #cj diameters4 ,the    
object-glass of the telescope should be 
covered with an opaque cap1 pierced by  
two circular holes about one-eighth of  
an inch in diameter and half an inch    
apart4 ,the holes should be on opposite 
sides of the centre of the object-glass 

and equidistant from it1 and the line   
joining the holes should be horizontal4 
,when this cap is removed the slit      
appears as a narrow vertical band with  
much fainter bands on both sides of it4 
,with the cap in place1 the central     
bright band appears to be ruled with    
narrow vertical lines or fringes        
produced by the interference99 of the   
two pencils of light coming through     
different parts of the object-glass from
 the distant slit4 ,cover one of the    
holes1 and the fringes instantly        
disappear4 ,their production requires   
the joint effect of the two             
light-pencils4  ,footnote 993 ,for an   
explanation of the phenomena of         
interference1 see any encyclopedia or   
book on physics4  ,now suppose the two  
holes over the object-glass to be in    
movable plates1 so that their distance  
apart can be varied4 ,as they are       
gradually separated the narrow vertical 
fringes become less and less distinct1  
and finally vanish completely4 ,measure 

the distance between the holes and      
divide this by the wavelength of light1 
which we may call #a_/ejjjj of an inch4 
,the result is the angular width of the 
distant slit4 ,knowing the distance of  
the slit1 we can at once calculate its  
linear width4 ,if for the slit we       
substitute a minute circular hole1 the  
method of measurement remains the same1 
but the angular diameter as calculated  
above must be multiplied by #a4bb499    
,footnote 993 ,more complete details may
 be found in ,michelson's ,lowell       
,lectures on ,light-,waves and ,their   
,uses1 ,university of ,chicago ,press1  
#aijg4  ,to measure the diameter of a   
star we proceed in a similar way1 but1  
as the angle it subtends is so small1 we
 must use a very large telescope1 for   
the smaller the angle the farther apart 
must be the two holes over the          
object-glass 7or the mirror1 in case a  
reflecting telescope is employed74 ,in  
fact1 when the holes are moved apart to 
the full aperture of the #ajj-;inch     

,hooker telescope1 the interference     
fringes are still visible even with the 
star ,betelgeuse1 though its angular    
diameter is perhaps as great as that of 
any other star4 ,thus1 we must build an 
attachment for the telescope1 so        
arranged as to permit us to move the    
openings still farther apart4           
,illustration3 ,fig4 #bc4 ,diagram      
showing outline of the #ajj-;inch       
,hooker telescope1 and path of the two  
pencils of light from a star when under 
observation with the #bj-;foot          
,michelson interferometer4  ,a          
photograph of the interferometer is     
shown in ,fig4 #bd4  ,,the #bj-;,,foot  
,,instrument  ,the #bj-;foot            
interferometer designed by ,messrs4     
,michelson and ,pease1 and constructed  
in the ,mount ,wilson ,observatory      
instrument-shop1 is shown in the diagram
 7,fig4 #bc7 and in a photograph of the 
upper end of the skeleton tube of the   
telescope 7,fig4 #bd74 ,the light from  
the star is received by two flat mirrors

 7,ml1 ,m#d7 which project beyond the   
tube and can be moved apart along the   
supporting arm4 ,these take the place of
 the two holes over the object-glass in 
our experiment4 ,from these mirrors the 
light is reflected to a second pair of  
flat mirrors 7,m#b1 ,m#c71 which send it
 toward the #ajj-;inch concave mirror   
7,m#e7 at the bottom of the telescope   
tube4 ,after this the course of the     
light is exactly as it would be if the  
mirrors ,m#b1 ,m#c were replaced by two 
holes over the #ajj-;inch mirror4 ,it is
 reflected to the convex mirror 7,m#f71 
then back in a less rapidly convergent  
beam toward the large mirror4 ,before   
reaching it the light is caught by the  
plane mirror 7,m#g7 and reflected       
through an opening at the side of the   
telescope tube to the eye-piece ,e4     
,here the fringes are observed with a   
magnification ranging from #a1ejj to    
#c1jjj diameters4  ,illustration3 ,fig4 
#bd4 ,twenty-foot ,michelson            
interferometer for measuring star       

diameters1 attached to upper end of the 
skeleton tube of the #ajj-;inch ,hooker 
telescope4  ,the path of the two pencils
 of light from the star is shown in     
,fig4 #bc4 ,for a photograph of the     
entire telescope1 see ,fig4 #d4  ,in the
 practical application of this method to
 the measurement of star diameters1 the 
chief problem was whether the atmosphere
 would be quiet enough to permit sharp  
interference fringes to be produced with
 light-pencils more than #ajj inches    
apart4 ,after successful preliminary    
tests with the #dj-;inch refracting     
telescope of the ,yerkes ,observatory1  
,professor ,michelson made the first    
attempt to see the fringes with the     
#fj-;inch and #ajj-;inch reflectors on  
,mount ,wilson in ,september1 #aiai4 ,he
 was surprised and delighted to find    
that the fringes were perfectly sharp   
and distinct with the full aperture of  
both these instruments4 ,doctor         
,anderson1 of the observatory staff1    
then devised a special form of          

interferometer for the measurement of   
close double stars1 and applied it with 
the #ajj-;inch telescope to the         
measurement of the orbital motion of the
 close components of ,capella1 with     
results of extraordinary accuracy1 far  
beyond anything attainable by previous  
methods4 ,the success of this work      
strongly encouraged the more ambitious  
project of measuring the diameter of a  
star1 and the #bj-;foot interferometer  
was built for this purpose4  ,the       
difficult and delicate problem of       
adjusting the mirrors of this instrument
 with the necessary extreme accuracy was
 solved by ,professor ,michelson during 
his visit to ,mount ,wilson in the      
summer of #aibj1 and with the assistance
 of ,mr4 ,pease1 of the observatory     
staff1 interference fringes were        
observed in the case of certain stars   
when the mirrors were as much as #ah    
feet apart4 ,all was thus in readiness  
for a decisive test as soon as a        
suitable star presented itself4  ,,the  

,,giant ,,betelgeuse  ,russell1         
,shapley1 and ,eddington had pointed out
 ,betelgeuse 7,arabic for the giant's   
shoulder71 the bright red star in the   
constellation of ,orion 7,fig4 #be71 as 
the most favorable of all stars for     
measurement1 and the last-named had     
given its angular diameter as #j4jea of 
a second of arc4 ,this deduction from   
theory appeared in his recent           
presidential address before the ,british
 ,association for the ,advancement of   
,science1 in which ,professor ,eddington
 remarked3 ,probably the greatest need  
of stellar astronomy at the present day1
 in order to make sure that our         
theoretical deductions are starting on  
the right lines1 is some means of       
measuring the apparent angular diameter 
of stars4 ,he then referred to the work 
already in progress on ,mount ,wilson1  
but anticipated that atmospheric        
disturbance will ultimately set the     
limit to what can be accomplished4      
,illustration3 ,fig4 #be4 ,the giant    

,betelgeuse 7within the circle71        
familiar as the conspicuous red star in 
the right shoulder of ,orion 7,hubble74 
,measures with the interferometer show  
its angular diameter to be #j4jdg of a  
second of arc1 corresponding to a linear
 diameter of #bae1jjj1jjj miles1 if the 
best available determination of its     
distance can be relied upon4 ,this      
determination shows ,betelgeuse to be   
#afj light-years from the earth4 ,light 
travels at the rate of #ahf1jjj miles   
per second1 and yet spends #afj years on
 its journey to us from this star4  ,on 
,december #ac1 #aibj1 ,mr4 ,pease       
successfully measured the diameter of   
,betelgeuse with the #bj-;foot          
interferometer4 ,as the outer mirrors   
were separated the interference fringes 
gradually became less distinct1 as      
theory requires1 and as ,doctor ,merrill
 had previously seen when observing     
,betelgeuse with the interferometer used
 for ,capella4 ,at a separation of #aj  
feet the fringes disappeared completely1

 giving the data required for           
calculating the diameter of the star4   
,to test the perfection of the          
adjustment1 the telescope was turned to 
other stars1 of smaller angular         
diameter1 which showed the fringes with 
perfect clearness4 ,turning back to     
,betelgeuse1 they were seen beyond doubt
 to be absent4 ,assuming the mean       
wave-length of the light of this star to
 be #egej_/ajjjjjjj of a millimetre1 its
 angular diameter comes out #j4jdg of a 
second of arc1 thus falling between the 
values--#j4jea and #j4jca of a          
second--predicted by ,eddington and     
,russell from slightly different        
assumptions4 ,subsequent corrections and
 repeated measurement will change ,mr4  
,pease's result somewhat1 but it is     
almost certainly within #aj or #ae per  
cent of the truth4 ,we may therefore    
conclude that the angular diameter of   
,betelgeuse is very nearly the same as  
that of a ball one inch in diameter1    
seen at a distance of seventy miles4    

,illustration3 ,fig4 #bf4 ,arcturus     
7within the white circle71 known to the 
,arabs as the ,lance ,bearer1 and to the
 ,chinese as the ,great ,horn or the    
,palace of the ,emperors 7,hubble74     
,its angular diameter1 measured at      
,mount ,wilson by ,pease with the       
#bj-;foot ,michelson interferometer on  
,april #ae1 #aiba1 is #j4jbb of a       
second1 in close agreement with         
,russell's predicted value of #j4jai of 
a second4 ,the mean parallax of         
,arcturus1 based upon several           
determinations1 is #j4jie of a second1  
corresponding to a distance of #cd      
light-years4 ,the linear diameter1      
computed from ,pease's measure and this 
value of the distance is about #ba      
million miles4  ,but this represents    
only the angle subtended by the star's  
disk4 ,to learn its linear diameter1 we 
must know its distance4 ,four           
determinations of the parallax1 which   
determines the distance1 have been made4
 ,elkin1 with the ,yale heliometer1     

obtained #j4jcb of a second of arc4     
,schlesinger1 from photographs taken    
with the #cj-;inch ,allegheny refractor1
 derived #j4jaf4 ,adams1 by his         
spectroscopic method applied with the   
#fj-;inch ,mount ,wilson reflector1     
obtained #j4jab4 ,lee's recent value1   
secured photographically with the       
#dj-;inch ,yerkes refractor1 is #j4jbb4 
,the heliometer parallax is doubtless   
less reliable than the photographic     
ones1 and ,doctor ,adams states that the
 spectral type and luminosity of        
,betelgeuse make his value less certain 
than in the case of most other stars4   
,if we take a 7weighted7 mean value of  
#j4jbj of a second1 we shall probably   
not be far from the truth4 ,this        
parallax represents the angle subtended 
by the radius of the earth's orbit      
7#ic1jjj1jjj miles7 at the distance of  
,betelgeuse4 ,by comparing it with      
#j4jdg1 the angular diameter of the     
star1 we see that the linear diameter is
 about two and one-third times as great 

as the distance from the earth to the   
sun1 or approximately #bae1jjj1jjj      
miles4 ,thus1 if this measure of its    
distance is not considerably in error1  
,betelgeuse would nearly fill the orbit 
of ,mars4 ,all methods of determining   
the distances of the stars are subject  
to uncertainty1 however1 and subsequent 
measures may reduce this figure very    
appreciably4 ,but there can be no doubt 
that the diameter of ,betelgeuse exceeds
 #ajj1jjj1jjj miles1 and it is probably 
much greater4  ,the extremely small     
angle subtended by this enormous disk is
 explained by the great distance of the 
star1 which is about #afj light-years4  
,that is to say1 light travelling at the
 rate of #ahf1jjj miles per second      
spends #afj years in crossing the space 
that lies between us and ,betelgeuse1   
whose tremendous proportions therefore  
seem so minute even in the most powerful
 telescopes4  ,,stellar ,,evolution     
,this actual measure of the diameter of 
,betelgeuse supplies a new and striking 

test of ,russell's and ,hertzsprung's   
theory of dwarf and giant stars4 ,just  
before the war ,russell showed that our 
old methods of classifying the stars    
according to their spectra must be      
radically changed4 ,stars in an early   
stage of their life history may be      
regarded as diffuse gaseous masses1     
enormously larger than our sun1 and at a
 much lower temperature4 ,their density 
must be very low1 and their state that  
of a perfect gas4 ,these are the giants4
 ,in the slow process of time they      
contract through constant loss of heat  
by radiation4 ,but1 despite this loss1  
the heat produced by contraction and    
from other sources 7see p4 #hb7 causes  
their temperature to rise1 while their  
color changes from red to bluish white4 
,the process of shrinkage and rise of   
temperature goes on so long as they     
remain in the state of a perfect gas4   
,but as soon as contraction has         
increased the density of the gas beyond 
a certain point the cycle reverses and  

the temperature begins to fall4 ,the    
bluish-white light of the star turns    
yellowish1 and we enter the dwarf stage1
 of which our own sun is a              
representative4 ,the density increases1 
surpassing that of water in the case of 
the sun1 and going far beyond this point
 in later stages4 ,in the lapse of      
millions of years a reddish hue appears1
 finally turning to deep red4 ,the      
falling temperature permits the chemical
 elements1 existing in a gaseous state  
in the outer atmosphere of the star1 to 
unite into compounds1 which are rendered
 conspicuous by their characteristic    
bands in the spectrum4 ,finally comes   
extinction of light1 as the star        
approaches its ultimate state of a cold 
and solid globe4  ,illustration3 ,fig4  
#bg4 ,the giant star ,antares 7within   
the white circle71 notable for its red  
color in the constellation ,scorpio1 and
 named by the ,greeks ,a ,rival of ,mars
 7,hubble74  ,the distance of ,antares1 
though not very accurately known1 is    

probably not far from #cej light-years4 
,its angular diameter of #j4jdj of a    
second would thus correspond to a linear
 diameter of about #djj million miles4  
,we may thus form a new picture of the  
two branches of the temperature curve1  
long since suggested by ,lockyer1 on    
very different grounds1 as the outline  
of stellar life4 ,on the ascending side 
are the giants1 of vast dimensions and  
more diffuse than the air we breathe4   
,there are good reasons for believing   
that the mass of ,betelgeuse cannot be  
more than ten times that of the sun1    
while its volume is at least a million  
times as great and may exceed eight     
million times the sun's volume4         
,therefore1 its average density must be 
like that of an attenuated gas in an    
electric vacuum tube4 ,three-quarters of
 the naked-eye stars are in the giant   
stage1 which comprises such familiar    
objects as ,betelgeuse1 ,antares1 and   
,aldebaran1 but most of them are much   
denser than these greatly inflated      

bodies4 ,the pinnacle is reached in the 
intensely hot white stars of the helium 
class1 in whose spectra the lines of    
this gas are very conspicuous4 ,the     
density of these stars is perhaps       
one-tenth that of the sun4 ,sirius1 also
 very hot1 is nearly twice as dense4    
,then comes the cooling stage1          
characterized1 as already remarked1 by  
increasing density1 and also by         
increasing chemical complexity resulting
 from falling temperature4 ,this life   
cycle is probably not followed by all   
stars1 but it may hold true for millions
 of them4  ,the existence of giant and  
dwarf stars has been fully proved by the
 remarkable work of ,adams and his      
associates on ,mount ,wilson1 where his 
method of determining a star's distance 
and intrinsic luminosity by             
spectroscopic observations has already  
been applied to #b1jjj stars4           
,discussion of the results leads at once
 to the recognition of the two great    
classes of giants and dwarfs4 ,now comes

 the work of ,michelson and ,pease to   
cap the climax1 giving us the actual    
diameter of a typical giant star1 in    
close agreement with predictions based  
upon theory4 ,from this diameter we may 
conclude that the density of ,betelgeuse
 is extremely low1 in harmony with      
,russell's theory1 which is further     
supported by spectroscopic analysis of  
the star's light1 revealing evidence of 
the comparatively low temperature called
 for by the theory at this early stage  
of stellar existence4  ,,two ,,other    
,,giants  ,the diameter of ,arcturus was
 successfully measured by ,mr4 ,pease at
 ,mount ,wilson on ,april #ae4 ,as the  
mirrors of the interferometer were moved
 apart1 the fringes gradually decreased 
in visibility until they finally        
disappeared at a mirror separation of   
#ai4f feet4 ,adopting a mean wave-length
 of #efjj_/ajjjjjjj of a millimetre for 
the light of ,arcturus1 this gives a    
value of #j4jbb of a second of arc for  
the angular diameter of the star4 ,if we

 use a mean value of #j4jie of a second 
for the parallax1 the corresponding     
linear diameter comes out #ba1jjj1jjj   
miles4 ,the angular diameter1 as in the 
case of ,betelgeuse1 is in remarkably   
close agreement with the diameter       
predicted from theory4 ,antares1 the    
third star measured by ,mr4 ,pease1 is  
the largest of all4 ,if it is actually a
 member of the ,scorpius-,centaurus     
group1 as we have strong reason to      
believe1 it is fully #cej light-years   
from the earth1 and its diameter is     
about #djj1jjj1jjj miles4               
,illustration3 ,fig4 #bh4 ,diameters of 
the ,sun1 ,arcturus1 ,betelgeuse1 and   
,antares compared with the orbit of     
,mars4  ,sun1 diameter1 #hfe1jjj miles4 
,arcturus1 diameter1 #ba1jjj1jjj miles4 
,betelgeuse1 diameter1 #bae1jjj1jjj     
miles4  ,antares1 diameter1 #djj1jjj1jjj
 miles4  ,it now remains to make further
 measures of ,betelgeuse1 especially    
because its marked changes in brightness
 suggest possible variations in         

diameter4 ,we must also apply the       
interferometer method to stars of the   
various spectral types1 in order to     
afford a sure basis for future studies  
of stellar evolution4 ,unfortunately1   
only a few giant stars are certain to   
fall within the range of our present    
instrument4 ,an interferometer of       
#gj-;feet aperture would be needed to   
measure ,sirius accurately1 and one of  
twice this size to deal with less       
brilliant white stars4 ,a #ajj-;foot    
instrument1 if feasible to build1 would 
permit objects representing most of the 
chief stages of stellar development to  
be measured1 thus contributing in the   
highest degree to the progress of our   
knowledge of the life history of the    
stars4 ,fortunately1 though the         
mechanical difficulties are great1 the  
optical problem is insignificant1 and   
the cost of the entire apparatus1 though
 necessarily high1 would be only a small
 fraction of that of a telescope of     
corresponding aperture1 if such could be

 built4 ,a #ajj-;foot interferometer    
might be designed in many different     
forms1 and one of these may ultimately  
be found to be within the range of      
possibility4 ,meanwhile the #bj-;foot   
interferometer has been improved so     
materially that it now promises to yield
 approximate measures of stars at first 
supposed to be beyond its capacity4     
,illustration3 ,fig4 #bi4 ,aldebaran1   
the leader 7of the ,pleiades71 was also 
known to the ,arabs as ,the ,eye of the 
,bull1 ,the ,heart of the ,bull1 and    
,the ,great ,camel 7,hubble74  ,like    
,betelgeuse and ,antares1 it is notable 
for its red color1 which accounts for   
the fact that its image on this         
photograph is hardly more conspicuous   
than the images of stars which are      
actually much fainter but contain a     
larger proportion of blue light1 to     
which the photographic plates here      
employed are more sensitive than to red 
or yellow4 ,aldebaran is about #ej      
light-years from the earth4             

,interferometer measures1 now in        
progress on ,mount ,wilson1 indicate    
that its angular diameter is about      
#j4jbj of a second4  ,while the theory  
of dwarf and giant stars and the        
measurements just described afford no   
direct evidence bearing on ,laplace's   
explanation of the formation of planets1
 they show that stars exist which are   
comparable in diameter with our solar   
system1 and suggest that the sun must   
have shrunk from vast dimensions4 ,the  
mode of formation of systems like our   
own1 and of other systems numerously    
illustrated in the heavens1 is one of   
the most fascinating problems of        
astronomy4 ,much light has been thrown  
on it by recent investigations1 rendered
 possible by the development of new and 
powerful instruments and by advances in 
physics of the most fundamental         
character4 ,all the evidence confirms   
the existence of dwarf and giant stars1 
but much work must be done before the   
entire course of stellar evolution can  

be explained4     ,,chapter ,,iii       
,,cosmic ,,crucibles  ,shelter during   
,raids1 marking the entrance to         
underground passages1 was a sign of     
common occurrence and sinister          
suggestion throughout ,london during the
 war4 ,with characteristic ingenuity and
 craftiness1 ostensibly for purposes of 
peace but with bomb-carrying capacity as
 a prime specification1 the ,zeppelin   
had been developed by the ,germans to a 
point where it seriously threatened both
 ,london and ,paris4 ,searchlights1     
range-finders1 and anti-aircraft guns1  
surpassed by the daring ventures of     
,british and ,french airmen1 would have 
served but little against the night     
invader except for its one fatal        
defect--the inflammable nature of the   
hydrogen gas that kept it aloft4 ,a     
single explosive bullet served to       
transform a ,zeppelin into a heap of    
scorched and twisted metal4 ,this       
characteristic of hydrogen caused the   
failure of the ,zeppelin raids4  ,had   

the war lasted a few months longer1     
however1 the work of ,american          
scientists would have made our          
counter-attack in the air a formidable  
one4 ,at the signing of the armistice   
hundreds of cylinders of compressed     
helium lay at the docks ready for       
shipment abroad4 ,extracted from the    
natural gas of ,texas wells by new and  
ingenious processes1 this substitute for
 hydrogen1 almost as light and          
absolutely uninflammable1 produced in   
quantities of millions of cubic feet1   
would have made the dirigibles of the   
,allies masters of the air4 ,the special
 properties of this remarkable gas1     
previously obtainable only in minute    
quantities1 would have sufficed to      
reverse the situation4  ,,solar ,,helium
  ,helium1 as its name implies1 is of   
solar origin4 ,in #ahfh1 when ,lockyer  
first directed his spectroscope to the  
great flames or prominences that rise   
thousands of miles1 sometimes hundreds  
of thousands1 above the surface of the  

sun1 he instantly identified the        
characteristic red and blue radiations  
of hydrogen4 ,in the yellow1 close to   
the position of the well-known double   
line of sodium1 but not quite coincident
 with it1 he detected a new line1 of    
great brilliancy1 extending to the      
highest levels4 ,its similarity in this 
respect with the lines of hydrogen led  
him to recognize the existence of a new 
and very light gas1 unknown to          
terrestrial chemistry4  ,many years     
passed before any chemical laboratory on
 earth was able to match this product of
 the great laboratory of the sun4 ,in   
#ahif ,ramsay at last succeeded in      
separating helium1 recognized by the    
same yellow line in its spectrum1 in    
minute quantities from the mineral      
uraninite4 ,once available for study    
under electrical excitation in vacuum   
tubes1 helium was found to have many    
other lines in its spectrum1 which have 
been identified in the spectra of solar 
prominences1 gaseous nebul1 and hot     

stars4 ,indeed1 there is a stellar class
 known as helium stars1 because of the  
dominance of this gas in their          
atmospheres4  ,illustration3 ,fig4 #cj4 
,solar prominences1 photographed with   
the spectroheliograph without an eclipse
 7,ellerman74  ,in these luminous       
gaseous clouds1 which sometimes rise to 
elevations exceeding half the sun's     
diameter1 the new gas helium was        
discovered by ,lockyer in #ahfh4 ,helium
 was not found on the earth until #ahif4
 ,since then it has been shown to be a  
prominent constituent of nebul and hot  
stars4  ,the chief importance of helium 
lies in the clue it has afforded to the 
constitution of matter and the          
transmutation of the elements4 ,radium  
and other radioactive substances1 such  
as uranium1 spontaneously emit          
negatively charged particles of         
extremely small mass 7electrons71 and   
also positively charged particles of    
much greater mass1 known as alpha       
particles4 ,rutherford and ,geiger      

actually succeeded in counting the      
number of alpha particles emitted per   
second by a known mass of radium1 and   
showed that these were charged helium   
atoms4  ,to discuss more at length the  
extraordinary characteristics of helium1
 which plays so large a part in         
celestial affairs1 would take us too far
 afield4 ,let us therefore pass to      
another case in which a fundamental     
discovery1 this time in physics1 was    
first foreshadowed by astronomical      
observation4  ,,sun-,,spots ,,as        
,,magnets  ,no archologist1 whether     
,young or ,champollion deciphering the  
,rosetta ,stone1 or ,rawlinson copying  
the cuneiform inscription on the cliff  
of ,behistun1 was ever faced by a more  
fascinating problem than that which     
confronts the solar physicist engaged in
 the interpretation of the hieroglyphic 
lines of sun-spot spectra4 ,the colossal
 whirling storms that constitute        
sun-spots1 so vast that the earth would 
make but a moment's scant mouthful for  

them1 differ materially from the general
 light of the sun when examined with the
 spectroscope4 ,observing them visually 
many years ago1 the late ,professor     
,young1 of ,princeton1 found among their
 complex features a number of double    
lines which he naturally attributed1 in 
harmony with the physical knowledge of  
the time1 to the effect of reversal by  
superposed layers of vapors of different
 density and temperature4 ,what he      
actually saw1 however1 as was proved at 
the ,mount ,wilson ,observatory in      
#aijh1 was the effect of a powerful     
magnetic field on radiation1 now known  
as the ,zeeman effect4  ,illustration3  
,fig4 #ca4 ,the #aej-;foot tower        
telescope of the ,mount ,wilson         
,observatory4  ,an image of the sun     
about #af inches in diameter is formed  
in the laboratory at the base of the    
tower4 ,below this1 in a well extending 
#hj feet into the earth1 is the powerful
 spectroscope with which the magnetic   
fields in sun-spots and the general     

magnetic field of the sun are studied4  
,faraday was the first to detect the    
influence of magnetism on light4        
,between the poles of a large           
electromagnet1 powerful for those days  
7#ahde71 he placed a block of very dense
 glass4 ,the plane of polarization of a 
beam of light1 which passed unaffected  
through the glass before the switch was 
closed1 was seen to rotate when the     
magnetic field was produced by the flow 
of the current4 ,a similar rotation is  
now familiar in the well-known tests of 
sugars--lvulose and dextrose--which     
rotate plane-polarized light to left and
 right1 respectively4  ,but in this     
first discovery of a relationship       
between light and magnetism ,faraday had
 not taken the more important step that 
he coveted--to determine whether the    
vibration period of a light-emitting    
particle is subject to change in a      
magnetic field4 ,he attempted this in   
#ahfb--the last experiment of his life4 
,a sodium flame was placed between the  

poles of a magnet1 and the yellow lines 
were watched in a spectroscope when the 
magnet was excited4 ,no change could be 
detected1 and none was found by         
subsequent investigators until ,zeeman1 
of ,leiden1 with more powerful          
instruments made his famous discovery1  
the twenty-fifth anniversary of which   
has recently been celebrated4           
,illustration3 ,fig4 #cb4 ,pasadena     
,laboratory of the ,mount ,wilson       
,observatory4  ,showing the large magnet
 7on the left7 and the spectroscopes    
used for the study of the effect of     
magnetism on radiation4 ,a single line  
in the spectrum is split by the magnetic
 field into from three to twenty-one    
components1 as illustrated in ,fig4 #cd4
 ,the corresponding lines in the spectra
 of sun-spots are split up in precisely 
the same way1 thus indicating the       
presence of powerful magnetic fields in 
the sun4  ,his method of procedure was  
similar to ,faraday's1 but his magnet   
and spectroscope were much more         

powerful1 and a theory due to ,lorentz1 
predicting the nature of the change to  
be expected1 was available as a check on
 his results4 ,when the current was     
applied the lines were seen to widen4   
,in a still more powerful magnetic field
 each of them split into two components 
7when the observation was made along the
 lines of force71 and the light of the  
components of each line was found to be 
circularly polarized in opposite        
directions4 ,strictly in harmony with   
,lorentz's theory1 this splitting and   
polarization proved the presence in the 
luminous vapor of exactly such          
negatively charged electrons as had been
 indicated there previously by very     
different experimental methods4  ,in    
#aijh great cyclonic storms1 or         
vortices1 were discovered at the ,mount 
,wilson ,observatory centring in        
sun-spots4 ,such whirling masses of hot 
vapors1 inferred from ,sir ,joseph      
,thomson's results to contain           
electrically charged particles1 should  

give rise to a magnetic field4 ,this    
hypothesis at once suggested that the   
double lines observed by ,young might   
really represent the ,zeeman effect4    
,the test was made1 and all the         
characteristic phenomena of radiation in
 a magnetic field were found4  ,thus a  
great physical experiment is constantly 
being performed for us in the sun4      
,every large sunspot contains a magnetic
 field covering many thousands of square
 miles1 within which the spectrum lines 
of iron1 manganese1 chromium1 titanium1 
vanadium1 calcium1 and other metallic   
vapors are so powerfully affected that  
their widening and splitting can be seen
 with telescopes and spectroscopes of   
moderate size4  ,,the ,,tower           
,,telescope  ,both of these             
illustrations show how the physicist and
 chemist1 when adequately armed for     
astronomical attack1 can take advantage 
in their studies of the stupendous      
processes visible in cosmic crucibles1  
heated to high temperatures and         

influenced1 as in the case of sun-spots1
 by intense magnetic fields4 ,certain   
modern instruments1 like the #fj-;foot  
and #aej-;foot tower telescopes on      
,mount ,wilson1 are especially designed 
for observing the course of these       
experiments4 ,the second of these       
telescopes produces at a fixed point in 
a laboratory an image of the sun about  
#af inches in diameter1 thus enlarging  
the sun-spots to such a scale that the  
magnetic phenomena of their various     
parts can be separately studied4 ,this  
analysis is accomplished with a         
spectroscope #hj feet in length1 mounted
 in a subterranean chamber beneath the  
tower4 ,the varied results of such      
investigations cannot be described here4
 ,only one of them may be mentioned--the
 discovery that the entire sun1 rotating
 on its axis1 is a great magnet4 ,hence 
we may reasonably infer that every star1
 and probably every planet1 is also a   
magnet1 as the earth has been known to  
be since the days of ,gilbert's ,de     

,magnete4 ,here lies one of the best    
clues for the physicist who seeks the   
cause of magnetism1 and attempts to     
produce it1 as ,barnett has recently    
succeeded in doing1 by rapidly whirling 
masses of metal in the laboratory4      
,illustration3 ,fig4 #cc4 ,sun-spot     
vortex in the upper hydrogen atmosphere4
 7,benioff74  ,photographed with the    
spectroheliograph4 ,the electric vortex 
that causes the magnetic field of the   
spot lies at a lower level1 and is not  
shown by such photographs4  ,perhaps a  
word of caution should be interpolated  
at this point4 ,solar magnetism in no   
wise accounts for the sun's             
gravitational power4 ,indeed1 its       
attraction cannot be felt by the most   
delicate instruments at the distance of 
the earth1 and would still be unknown   
were it not for the influence of        
magnetism on light4  ,auroras1 magnetic 
storms1 and such electric currents as   
those that recently deranged several    
,atlantic cables are due1 not to the    

magnetism of the sun or its spots1 but  
probably to streams of electrons1 shot  
out from highly disturbed areas of the  
solar surface surrounding great         
sun-spots1 traversing ninety-three      
million miles of the ether of space1 and
 penetrating deep into the earth's      
atmosphere4 ,these striking phenomena   
lead us into another chapter of physics1
 which limitations of space forbid us to
 pursue4  ,,stellar ,,chemistry  ,let us
 turn again to chemistry1 and see where 
experiments performed in cosmic         
laboratories can serve as a guide to the
 investigator4 ,a spinning solar        
tornado1 incomparably greater in scale  
than the devastating whirlwinds that so 
often cut narrow paths of destruction   
through town and country in the ,middle 
,west1 gradually gives rise to a        
sun-spot4 ,the expansion produced by the
 centrifugal force at the centre of the 
storm cools the intensely hot gases of  
the solar atmosphere to a point where   
chemical union can occur4 ,titanium and 

oxygen1 too hot to combine in most      
regions of the sun1 join to form the    
vapor of titanium oxide1 characterized  
in the sunspot spectrum by fluted bands1
 made up of hundreds of regularly spaced
 lines4 ,similarly magnesium and        
hydrogen combine as magnesium hydride   
and calcium and hydrogen form calcium   
hydride4 ,none of these compounds1      
stable at the high temperatures of      
sun-spots1 has been much studied in the 
laboratory4 ,the regions in which they  
exist1 though cooler than the general   
atmosphere of the sun1 are at           
temperatures of several thousand        
degrees1 attained in our laboratories   
only with the aid of such devices as    
powerful electric furnaces4             
,illustration3 ,fig4 #cd4 ,splitting of 
spectrum lines by a magnetic field      
7,babcock74  ,the upper and lower strips
 show lines in the spectrum of chromium1
 observed without a magnetic field4     
,when subjected to the influence of     
magnetism1 these single lines are split 

into several components4 ,thus the first
 line on the right is resolved by the   
field into three components1 one of     
which 7plane polarized7 appears in the  
second strip1 while the other two1 which
 are polarized in a plane at right      
angles to that of the middle component1 
are shown on the third strip4 ,the next 
line is split by the magnetic field into
 twelve components1 four of which appear
 in the second strip and eight in the   
third4 ,the magnetic fields in sun-spots
 affect these lines in precisely the    
same way4  ,it is interesting to follow 
our line of reasoning to the stars1     
which differ widely in temperature at   
various stages in their life-cycle499 ,a
 sun-spot is a solar tornado1 wherein   
the intensely hot solar vapors are      
cooled by expansion1 giving rise to the 
compounds already named4 ,a red star1 in
 ,russell's scheme of stellar evolution1
 is a cooler sun1 vast in volume and far
 more tenuous than atmospheric air when 
in the initial period of the giant      

stage1 but compressed and denser than   
water in the dwarf stage1 into which our
 sun has already entered as it gradually
 approaches the last phases of its      
existence4 ,therefore we should find1   
throughout the entire atmosphere of such
 stars1 some of the same compounds that 
are produced within the comparatively   
small limits of a sun-spot4 ,this1 of   
course1 on the correct assumption that  
sun and stars are made of the same      
substances4 ,fowler has already         
identified the bands of titanium oxide  
in such red stars as the giant          
,betelgeuse1 and in others of its class4
 ,it is safe to predict that an         
interesting chapter in the chemistry of 
the future will be based upon the study 
of such compounds1 both in the          
laboratory and under the progressive    
temperature conditions afforded by the  
countless stellar giants and dwarfs that
 precede and follow the solar state4    
,footnote 993 ,see ,chapter ,,ii4       
,illustration3 ,fig4 #ce4 ,electric     

furnace in the ,pasadena laboratory of  
the ,mount ,wilson ,observatory4  ,with 
which the chemical phenomena observed in
 sun-spots and red stars are            
experimentally imitated4                
,,astrophysical ,,laboratories  ,it is  
precisely in this long sequence of      
physical and chemical changes that the  
astrophysicist and the astrochemist can 
find the means of pushing home their    
attack4 ,it is true1 of course1 that the
 laboratory investigator has a great    
advantage in his ability to control his 
experiments1 and to vary their progress 
at will4 ,but by judicious use of the   
transcendental temperatures1 far out    
ranging those of his furnaces1 and      
extreme conditions1 which he can only   
partially imitate1 afforded by the sun1 
stars1 and nebul1 he may greatly widen  
the range of his inquiries4 ,the        
sequence of phenomena seen during the   
growth of a sun-spot1 or the observation
 of spots of different sizes1 and the   
long series of successive steps that    

mark the rise and decay of stellar life1
 resemble the changes that the          
experimenter brings about as he         
increases and diminishes the current in 
the coils of his magnet or raises and   
lowers the temperature of his electric  
furnace1 examining from time to time the
 spectrum of the glowing vapors1 and    
noting the changes shown by the varying 
appearance of their lines4              
,illustration3 ,fig4 #cf4 ,titanium     
oxide in red stars4  ,the upper spectrum
 is that of titanium in the flame of the
 electric arc1 where its combination    
with oxygen gives rise to the bands of  
titanium oxide 7,fowler74 ,the lower    
strip shows the spectrum of the red star
 ,mira 7,omicron ,ceti71 as drawn by    
,cortie at ,stonyhurst4 ,the bands of   
titanium oxide are clearly present in   
the star4  ,illustration3 ,fig4 #cg4    
,titanium oxide in sun-spots4  ,the     
upper strip shows a portion of the      
spectrum of a sun-spot 7,ellerman72 the 
lower one the corresponding region of   

the spectrum of titanium oxide 7,king74 
,the fluted bands of the oxide spectrum 
are easily identified in the spot1 where
 they indicate that titanium and oxygen1
 too hot to combine in the solar        
atmosphere1 unite in the spot because of
 the cooling produced by expansion in   
the vortex4  ,astronomical observations 
of this character1 it should be noted1  
are most effective when constantly      
tested and interpreted by laboratory    
experiment4 ,indeed1 a modern           
astrophysical observatory should be     
equipped like a great physical          
laboratory1 provided on the one hand    
with telescopes and accessory apparatus 
of the greatest attainable power1 and on
 the other with every device known to   
the investigator of radiation and the   
related physical and chemical phenomena4
 ,its telescopes1 especially designed   
with the aims of the physicist and      
chemist in view1 bring images of sun1   
stars1 nebul1 and other heavenly bodies 
within the reach of powerful            

spectroscopes1 sensitive bolometers and 
thermopiles1 and the long array of other
 appliances available for the           
measurement and analysis of radiation4  
,its electric furnaces1 arcs1 sparks1   
and vacuum tubes1 its apparatus for     
increasing and decreasing pressure1     
varying chemical conditions1 and        
subjecting luminous gases and vapors to 
the influence of electric and magnetic  
fields1 provide the means of imitating  
celestial phenomena1 and of repeating   
and interpreting the experiments        
observed at the telescope4 ,and the     
advantage thus derived1 as we have seen1
 is not confined to the astronomer1 who 
has often been able1 by making          
fundamental physical and chemical       
discoveries1 to repay his debt to the   
physicist and chemist for the apparatus 
and methods which he owes to them4      
,,newton ,,and ,,einstein  ,take1 for   
another example1 the greatest law of    
physics--,newton's law of gravitation4  
,huge balls of lead1 as used by         

,cavendish1 produce by their            
gravitational effect a minute rotation  
of a delicately suspended bar1 carrying 
smaller balls at its extremities4 ,but  
no such feeble means sufficed for       
,newton's purpose4 ,to prove the law of 
gravitation he had recourse to the      
tremendous pull on the moon of the      
entire mass of the earth1 and then      
extended his researches to the mutual   
attractions of all the bodies of the    
solar system4 ,later ,herschel applied  
this law to the suns which constitute   
double stars1 and to-day ,adams observes
 from ,mount ,wilson stars falling with 
great velocity toward the centre of the 
galactic system under the combined pull 
of the millions of objects that compose 
it4 ,thus full advantage has been taken 
of the possibility of utilizing the     
great masses of the heavenly bodies for 
the discovery and application of a law  
of physics and its reciprocal use in    
explaining celestial motions4           
,illustration3 ,fig4 #ch4 ,the          

,cavendish experiment4  ,two lead balls1
 each two inches in diameter1 are       
attached to the ends of a torsion rod   
six feet long1 which is suspended by a  
fine wire4 ,the experiment consists in  
measuring the rotation of the suspended 
system1 caused by the gravitational     
attraction of two lead spheres1 each    
twelve inches in diameter1 acting on the
 two small lead balls4  ,or consider the
 ,einstein theory of relativity1 the    
truth or falsity of which is no less    
fundamental to physics4 ,its inception  
sprang from the ,michelson-,morley      
experiment1 made in a laboratory in     
,cleveland1 which showed that motion of 
the earth through the ether of space    
could not be detected4 ,all of the three
 chief tests of ,einstein's general     
theory are astronomical--because of the 
great masses required to produce the    
minute effects predicted3 the motion of 
the perihelion of ,mercury1 the         
deflection of the light of a star by the
 attraction of the sun1 and the shift of

 the lines of the solar spectrum toward 
the red--questions not yet completely   
answered4  ,but it is in the study of   
the constitution of matter and the      
evolution of the elements1 the deepest  
and most critical problem of physics and
 chemistry1 that the extremes of        
pressure and temperature in the heavenly
 bodies1 and the prevalence of other    
physical conditions not yet successfully
 imitated on earth1 promise the greatest
 progress4 ,it fortunately happens that 
astrophysical research is now at the    
very apex of its development1 founded as
 it is upon many centuries of           
astronomical investigation1 rejuvenated 
by the introduction into the observatory
 of all the modern devices of the       
physicist1 and strengthened with        
instruments of truly extraordinary range
 and power4 ,these instruments bring    
within reach experiments that are in    
progress on some minute region of the   
sun's disk1 or in some star too distant 
even to be glimpsed with ordinary       

telescopes4 ,indeed1 the huge           
astronomical lenses and mirrors now     
available serve for these remote        
light-sources exactly the purpose of the
 lens or mirror employed by the         
physicist to project upon the slit of   
his spectroscope the image of a spark or
 arc or vacuum tube within which atoms  
and molecules are exposed to the        
influence of the electric discharge4    
,the physicist has the advantage of     
complete control over the experimental  
conditions1 while the astrophysicist    
must observe and interpret the          
experiments performed for him in remote 
laboratories4 ,in actual practice1 the  
two classes of work must be done in the 
closest conjunction1 if adequate        
utilization is to be made of either4    
,and this is only natural1 for the trend
 of recent research has made clear the  
fact that one of the three greatest     
problems of modern astronomy and        
astrophysics1 ranking with the structure
 of the universe and the evolution of   

celestial bodies1 is the constitution of
 matter4 ,let us see why this is so4    
,,transmutation ,,of ,,the ,,elements   
,the dream of the alchemist was to      
transmute one element into another1 with
 the prime object of producing gold4    
,such transmutation has been actually   
accomplished within the last few years1 
but the process is invariably one of    
disintegration--the more complex        
elements being broken up into simpler   
constituents4 ,much remains to be done  
in this same direction2 and here the    
stars and nebul1 which show the spectra 
of the elements under a great variety of
 conditions1 should help to point the   
way4 ,the progressive changes in        
spectra1 from the exclusive indications 
of the simple elements hydrogen1 helium1
 nitrogen1 possibly carbon1 and the     
terrestrially unknown gas nebulium in   
the gaseous nebul1 to the long list of  
familiar substances1 including several  
chemical compounds1 in the red stars1   
may prove to be fundamentally           

significant when adequately studied from
 the standpoint of the investigator of  
atomic structure4 ,the existing evidence
 seems to favor the view1 recently      
expressed by ,saha1 that many of these  
differences are due to varying degrees  
of ionization1 the outer electrons of   
the atoms being split off by high       
temperature or electrical excitation4   
,it is even possible that cosmic        
crucibles1 unrivalled by terrestrial    
ones1 may help materially to reveal the 
secret of the formation of complex      
elements from simpler ones4 ,physicists 
now believe that all of the elements are
 compounded of hydrogen atoms1 bound    
together by negative electrons4 ,thus   
helium is made up of four hydrogen      
atoms1 yet the atomic weight of helium  
7#d7 is less than four times that of    
hydrogen 7#a4jjh74 ,the difference may  
represent the mass of the electrical    
energy released when the transmutation  
occurred4  ,illustration3 ,fig4 #ci4    
,the ,trifid ,nebula in ,sagittarius    

7,ritchey74  ,the gas nebulium1 not yet 
found on the earth1 is the most         
characteristic constituent of irregular 
nebul4 ,nebulium is recognized by two   
green lines in its spectrum1 which cause
 the green color of nebul of the gaseous
 type4  ,eddington has speculated in a  
most interesting way on this possible   
source of stellar heat in his recent    
presidential address before the ,british
 ,association for the ,advancement of   
,science 7see ,nature1 ,september #b1   
#aibj74 ,he points out that the old     
contraction hypothesis1 according to    
which the source of solar and stellar   
heat was supposed to reside in the slow 
condensation of a radiating mass of gas 
under the action of gravity1 is wholly  
inadequate to explain the observed      
phenomena4 ,if the old view were        
correct1 the earlier history of a star1 
from the giant stage of a cool and      
diaphanous gas to the period of highest 
temperature1 would be run through within
 eighty thousand years1 whereas we have 

the best of evidence that many thousands
 of centuries would not suffice4 ,some  
other source of energy is imperatively  
needed4 ,if #e per cent of a star's mass
 consists originally of hydrogen atoms1 
which gradually combine in the slow     
process of time to form more complex    
elements1 the total heat thus liberated 
would more than suffice to account for  
all demands1 and it would be unnecessary
 to assume the existence of any other   
source of heat4  ,illustration3 ,fig4   
#dj4 ,spiral nebula in ,ursa ,major     
7,ritchey74  ,luminous matter1 in every 
variety of physical and chemical state1 
is available for study in the most      
diverse celestial objects1 from the     
spiral and irregular nebul through all  
the types of stars4 ,doctor van         
,maanen's measures of the ,mount ,wilson
 photographs indicate outward motion    
along the arms of spiral nebul1 while   
the spectroscope shows them to be       
whirling at enormous velocities4        
,,cosmic ,,pressures  ,this1 it may     

fairly be said1 is very speculative1 but
 the fact remains that celestial bodies 
appear to be the only places in which   
the complex elements may be in actual   
process of formation from their known   
source--hydrogen4 ,at least we may see  
what a vast variety of physical         
conditions these cosmic crucibles       
afford4 ,at one end of the scale we have
 the excessively tenuous nebul1 the     
luminosity of which1 mysterious in its  
origin1 resembles the electric glow in  
our vacuum tubes4 ,here we can detect   
only the lightest and simplest of the   
elements4 ,in the giant stars1 also     
extremely tenuous 7the density of       
,betelgeuse can hardly exceed           
one-thousandth of an atmosphere7 we     
observe the spectra of iron1 manganese1 
titanium1 calcium1 chromium1 magnesium1 
vanadium1 and sodium1 in addition to    
titanium oxide4 ,the outer part of these
 bodies1 from which light reaches us1   
must therefore be at a temperature of   
only a few thousand degrees1 but vastly 

higher temperatures must prevail at     
their centres4 ,in passing up the       
temperature curve more and more elements
 appear1 the surface temperature rises1 
and the internal temperature may reach  
millions of degrees4 ,at the same time  
the pressure within must also rise1     
reaching enormous figures in the last   
stages of stellar life4 ,cook has       
calculated that the pressure at the     
centre of the earth is between #d1jjj   
and #aj1jjj tons per square inch1 and   
this must be only a very small fraction 
of that attained within larger celestial
 bodies4 ,jeans has computed the        
pressure at the centre of two colliding 
stars as they strike and flatten1 and   
finds it may be of the order of         
#a1jjj1jjj1jjj tons per square          
inch--sufficient1 if their diameter be  
equal to that of the sun--to vaporize   
them #ajj1jjj times over4  ,compare     
these pressures with the highest that   
can be produced on earth4 ,if the       
,german gun that bombarded ,paris were  

loaded with a solid steel projectile of 
suitable dimensions1 a muzzle velocity  
of #f1jjj feet per second could be      
reached4 ,suppose this to be fired into 
a tapered hole in a great block of      
steel4 ,the instantaneous pressure1     
according to ,cook1 would be about      
#g1jjj tons per square inch1 only       
#a_/aejjjj of that possible through the 
collision of the largest stars4         
,illustration3 ,fig4 #da4 ,mount ,san   
,antonio as seen from ,mount ,wilson4   
,michelson is measuring the velocity of 
light between stations on ,mount ,wilson
 and ,mount ,san ,antonio4 ,astronomical
 observations afford the best means1    
however1 of detecting any possible      
difference between the velocities of    
light of different colors4 ,from studies
 of variable stars in the cluster       
,messier #e ,shapley concludes that if  
there is any difference between the     
velocities of blue and yellow light in  
free space it cannot exceed two inches  
in one second1 the time in which light  

travels #ahf1jjj miles4  ,finally1 we   
may compare the effects of light        
pressure on the earth and stars4 ,twenty
 years ago ,nichols and ,hull succeeded1
 with the aid of the most sensitive     
apparatus1 in measuring the minute      
displacements produced by the pressure  
of light4 ,the effect is so slight1 even
 with the brightest light-sources       
available1 that great experimental skill
 is required to measure it4 ,yet in the 
case of some of the larger stars        
,eddington calculates that one-half of  
their mass is supported by radiation    
pressure1 and this against their        
enormous gravitational attraction4 ,in  
fact1 if their mass were as great as ten
 times that of the sun1 the radiation   
pressure would so nearly overcome the   
pull of gravitation that they would be  
likely to break up4  ,but enough has    
been said to illustrate the wide variety
 of experimental devices that stand at  
our service in the laboratories of the  
heavens4 ,here the physicist and chemist

 of the future will more and more       
frequently supplement their terrestrial 
apparatus1 and find new clues to the    
complex problems which the amazing      
progress of recent years has already    
done so much to solve4  ,,practical     
,,value ,,of ,,researches ,,on ,,the    
,,constitution ,,of ,,matter  ,the      
layman has no difficulty in recognizing 
the practical value of researches       
directed toward the improvement of the  
incandescent lamp or the increased      
efficiency of the telephone4 ,he can see
 the results in the greatly decreased   
cost of electric illumination and the   
rapid extension of the range of the     
human voice4 ,but the very men who have 
made these advances1 those who have     
succeeded beyond all expectation in     
accomplishing the economic purposes in  
view1 are most emphatic in their        
insistence upon the importance of       
research of a more fundamental          
character4 ,thus ,vice-,president ,j4   
,j4 ,carty1 of the ,american ,telephone 

and ,telegraph ,company1 who directs its
 great ,department of ,development and  
,research1 and ,doctor ,w4 ,j4 ,whitney1
 ,director of the ,research ,laboratory 
of the ,general ,electric ,company1 have
 repeatedly expressed their indebtedness
 to the investigations of the physicist1
 made with no thought of immediate      
practical return4 ,faraday1 studying the
 laws of electricity1 discovered the    
principle which rendered the dynamo     
possible4 ,maxwell1 ,henry1 and ,hertz1 
equally unconcerned with material       
advantage1 made wireless telegraphy     
practicable4 ,in fact1 all truly great  
advances are thus derived from          
fundamental science1 and the future     
progress of the world will be largely   
dependent upon the provision made for   
scientific research1 especially in the  
fields of physics and chemistry1 which  
underlie all branches of engineering4   
,the constitution of matter1 therefore1 
instead of appealing as a subject to    
research only to the natural philosopher

 or to the general student of science1  
is a question of the greatest practical 
concern4 ,already the by-products of    
investigations directed toward its      
elucidation have been numerous and      
useful in the highest degree4 ,helium   
has been already cited2 ,x-rays hardly  
require mention2 radium1 which has so   
materially aided sufferers from cancer1 
is still better known4 ,wireless        
telephony and transcontinental telephony
 with wires were both rendered possible 
by studies of the nature of the electric
 discharge in vacuum tubes4 ,thus the   
practical man1 with his distrust of pure
 science1 need not resent investments   
made for the purpose of advancing our   
knowledge of such fundamental subjects  
as physics and chemistry4 ,on the       
contrary1 if true to his name1 he should
 help to multiply them many fold in the 
interest of economic and commercial     
development4