,,harper',s ,,library of ,,living       
,,thought       ,,are ,,the ,,planets   
,,inhabited8     ,,by ,e4 ,,walter      
,,maunder1 ,f4,r4,a4,s4                 
,,superintendent ,,of ,,the ,,solar     
,,department1   ,,royal ,,observatory   
,,greenwich    ,,author ,,of ,,astronomy
 ,,without ,a ,,telescope   ,,the       
,,royal ,,observatory1 ,,greenwich1     
,,its ,,history ,,and ,,work   ,,the    
,,astronomy ,,of ,,the ,,bible1 ,,the   
,,heavens ,,and ,,their ,,story   ,,etc4
     ,,harper  ,,brothers   ,,london    
,,and ,,new ,,york    #de ,,albemarle   
,,street1 ,w4   #aiac       ,published  
,march1 #aiac     ,,contents            
,,chapter                               
,,page       ,i4 ,,the ,,question       
,,stated                            #a  
,,ii4 ,,the ,,living ,,organism         
#f     ,,iii4 ,,the ,,sun               
#bj      ,,iv4 ,,the ,,distribution ,,of
 ,,the ,,elements ,,in ,,space     #cc  
,v4 ,,the ,,moon                        
#dc      ,,vi4 ,,the ,,canals ,,of      

,,mars                            #eg   
,,vii4 ,,the ,,condition ,,of ,,mars    
#ga    ,,viii4 ,,the ,,illusions ,,of   
,,mars                         #if      
,,ix4 ,,venus1 ,,mercury ,,and ,,the    
,,asteroids             #aaa       ,x4  
,,the ,,major ,,planets                 
#abb      ,,xi4 ,,when ,,the ,,major    
,,planets ,,cool                  #acc  
,,xii4 ,,the ,,final ,,question         
#adc          ,,index                   
#afc     ,,are ,,the ,,planets          
,,inhabited8     ,,chapter ,i  ,,the    
,,question ,,stated   ,the first thought
 that men had concerning the heavenly   
bodies was an obvious one3 they were    
lights4 ,there was a greater light to   
rule the day2 a lesser light to rule the
 night2 and there were the stars also4  
,in those days there seemed an immense  
difference between the earth upon which 
men stood1 and the bright objects that  
shone down upon it from the heavens     
above4 ,the earth seemed to be vast1    
dark1 and motionless2 the celestial     

lights seemed to be small1 and moved1   
and shone4 ,the earth was then regarded 
as the fixed centre of the universe1 but
 the ,copernican theory has since       
deprived it of this pride of place4 ,yet
 from another point of view the new     
conception of its position involves a   
promotion1 since the earth itself is now
 regarded as a heavenly body of the same
 order as some of those which shine down
 upon us4 ,it is amongst them1 and it   
too moves and shines--shines1 as some of
 them do1 by reflecting the light of the
 sun4 ,could we transport ourselves to a
 neighbouring world1 the earth would    
seem a star1 not distinguishable in kind
 from the rest4  ,but as men realized   
this1 they began to ask3 ,since this    
world from a distant standpoint must    
appear as a star1 would not a star1 if  
we could get near enough to it1 show    
itself also as a world8 ,this world     
teems with life2 above all1 it is the   
home of human life4 ,men and women1     
gifted with feeling1 intelligence1 and  

character1 look upward from its surface 
and watch the shining members of the    
heavenly host4 ,are none of these the   
home of beings gifted with like powers1 
who watch in their turn the movements of
 that shining point which is our world8 
,this is the meaning of the controversy 
on the ,plurality of ,worlds which      
excited so much interest some sixty     
years ago1 and has been with us more or 
less ever since4 ,it is the desire to   
recognize the presence in the orbs      
around us of beings like ourselves1     
possessed of personality and            
intelligence1 lodged in an organic body4
  ,this is what is meant when we speak  
of a world being inhabited4 ,it would   
not1 for example1 at all content us if  
we could ascertain that ,jupiter was    
covered by a shoreless ocean1 rich in   
every variety of fish2 or that the hard 
rocks of the ,moon were delicately      
veiled by lichens4 ,just as no richness 
of vegetation and no fulness and        
complexity of animal life would justify 

an explorer in describing some land that
 he had discovered as being inhabited if
 no men were there1 so we cannot rightly
 speak of any other world as being      
inhabited if it is not the home of      
intelligent life4 ,if the life did not  
rise above the level of algae or        
oysters1 the globe on which they        
flourish would be uninhabited in our    
estimation1 and its chief interest would
 lie in the possibility that in the     
course of ages life might change its    
forms and develop hereafter into        
manifestations with which we could claim
 a nearer kinship4  ,on the other hand1 
of necessity we are precluded from      
extending our enquiry to the case of    
disembodied intelligences1 if such be   
conceived possible4 ,all created        
existences must be conditioned1 but if  
we have no knowledge of what those      
conditions may be1 or means for         
attaining such knowledge1 we cannot     
discuss them4 ,nothing can be affirmed1 
nothing denied1 concerning the          

possibility of intelligences existing on
 the ,moon or even in the ,sun if we are
 unable to ascertain under what         
limitations those particular            
intelligences subsist4 ,gnomes1 sylphs1 
elves1 and fairies1 and all similar     
conceptions1 escape the possibility of  
discussion by our ignorance of their    
properties4 ,as nothing can be asserted 
of them they remain beyond              
investigation1 as they are beyond sight 
and touch4  ,the only beings1 then1 the 
presence of which would justify us in   
regarding another world as inhabited are
 such as would justify us in applying   
that term to a part of our own world4   
,they must possess intelligence and     
consciousness on the one hand2 on the   
other1 they must likewise have corporeal
 form4 ,true1 the form might be imagined
 as different from that we possess2 but1
 as with ourselves1 the intelligent     
spirit must be lodged in and expressed  
by a living material body4 ,our enquiry 
is thus rendered a physical one2 it is  

the necessities of the living body that 
must guide us in it2 a world unsuited   
for living organisms is not1 in the     
sense of this enquiry1 a habitable      
world4  ,the discussion1 as it was      
carried on sixty years ago by ,dr4      
,whewell and ,sir ,david ,brewster1 was 
essentially a metaphysical1 almost a    
theological one1 and it was chiefly     
considered in its supposed relationship 
to certain religious conceptions4 ,it   
was urged that it was derogatory to the 
wisdom and goodness of the ,creator to  
suppose that ,he would have created so  
many great and glorious orbs without    
having a definite purpose in so doing1  
and that the only purpose for which a   
world could be made was that it might be
 inhabited4 ,so1 again1 when ,dr4 ,a4   
,r4 ,wallace revived the discussion in  
#aijc1 he clearly had a theological     
purpose in his opening paper1 though he 
was taking the opposite view from that  
held by ,brewster half a century        
earlier4  ,for myself1 if there be any  

theological significance attaching to   
the solving of this problem1 ,i do not  
know what it is4 ,if we decide that     
there are very many inhabited worlds1 or
 that there are few1 or that there is   
but one--our own--,i fail to see how it 
should modify our religious beliefs4    
,for example3 explorers have made their 
way across the ,antarctic continent to  
the ,south ,pole but have found no      
inhabitant there4 ,has this fact any    
theological bearing8 or if1 on the      
contrary1 a race of men had been        
discovered there1 what change would it  
have made in the theological position of
 anyone8 ,and if this be so with regard 
to a new continent on this earth1 why   
should it be different with regard to   
the continents of another planet8  ,the 
problem therefore seems not to be       
theological or metaphysical1 but purely 
physical4 ,we have simply to ask with   
regard to each heavenly body which we   
pass in review3 ,are its physical       
conditions1 so far as we can ascertain  

them1 such as would render the          
maintenance of life possible upon it8   
,the question is not at all as to how   
life is generated on a world1 but as to 
whether1 if once in action on a         
particular world1 its activities could  
be carried on4     ,,chapter ,,ii  ,,the
 ,,living ,,organism   ,a world for     
habitation1 then1 is a world whereon    
living organisms can exist that are     
comparable in intelligence with men4    
,but men presuppose the existence of    
living organisms of inferior grades4    
,therefore a world for habitation must  
first of all be one upon which it is    
possible for living organisms1 as such1 
to exist4  ,it does not concern us in   
the present connection how life first   
came into existence on this planet4 ,it 
is sufficient that we know from         
experience that life does exist here2   
and in whatsoever way it was first      
generated here1 in that same way we may 
consider that it could have been        
generated on another planet4  ,nor need 

any question trouble us as to the       
precise line of demarkation to be drawn 
between inorganic and organic           
substances1 or amongst the latter1      
between plants and animals4 ,these are  
important subjects for discussion1 but  
they do not affect us here1 for we are  
essentially concerned with the highest  
form of organism1 the one furthest from 
these two dividing lines4  ,it suffices 
that living organisms do exist here1 and
 exist under well-defined conditions4   
,wanting these conditions1 they perish4 
,we can1 to a varying degree1 determine 
the physical conditions prevailing upon 
the heavenly bodies1 and we can         
ascertain whether these physical        
conditions would be favourable1         
unfavourable1 or fatal to the living    
organism4  ,what is a living organism8  
,a living organism is such that1 though 
it is continually changing its          
substance1 its identity1 as a whole1    
remains essentially the same4 ,this     
definition is incomplete1 but it gives  

us a first essential approximation1 it  
indicates the continuance of the whole1 
with the unceasing change of the        
details4 ,were this definition complete1
 a river would furnish us with a perfect
 example of a living organism1 because1 
while the river remains1 the individual 
drops of water are continually changing4
 ,there is then something more in the   
living organism than the continuity of  
the whole1 with the change of the       
details4  ,an analogy1 given by ,max    
,verworn1 carries us a step further4 ,he
 likens life to a flame1 and takes a gas
 flame with its butterfly shape as a    
particularly appropriate illustration4  
,here the shape of the flame remains    
constant1 even in its details4          
,immediately above the burner1 at the   
base of the flame1 there is a completely
 dark space2 surrounding this1 a bluish 
zone that is faintly luminous2 and      
beyond this again1 the broad spread of  
the two wings that are brightly         
luminous4 ,the flame1 like the river1   

preserves its identity of form1 while   
its constituent details--the gases that 
feed it--are in continual change4 ,but  
there is not only a change of material  
in the flame2 there is a change of      
condition4 ,everywhere the gas from the 
burner is entering into energetic       
combination with the oxygen of the air1 
with evolution of light and heat4 ,there
 is change in the constituent particles 
as well as change of the constituent    
particles2 there is more than the mere  
flux of material through the form2 there
 is change of the material1 and in the  
process of that change energy is        
developed4  ,a steam-engine may afford  
us a third illustration4 ,here fresh    
material is continually being introduced
 into the engine there to suffer change4
 ,part is supplied as fuel to the fire  
there to maintain the temperature of the
 engine2 so far the illustration is     
analogous to that of the gas flame4 ,but
 the engine carries us a step further1  
for part of the material supplied to it 

is water1 which is converted into steam 
by the heat of the fire1 and from the   
expansion of the steam the energy sought
 from the machine is derived4 ,here     
again we have change in the material    
with development of energy2 but there is
 not only work done in the subject1     
there is work done by it4  ,but the     
living organism differs from artificial 
machines in that1 of itself and by      
itself1 it is continuously drawing into 
itself non-living matter1 converting it 
into an integral part of the organism1  
and so endowing it with the qualities of
 life4 ,and from this non-living matter 
it derives fresh energy for the carrying
 on of the life of the organism4  ,the  
engine and the butterfly gas flame do   
not give us1 any more than the river1 a 
complete picture of the living organism4
 ,the form of the river is imposed upon 
it from without2 the river is defined by
 its bed1 by the contour of the country 
through which it flows4 ,the form and   
size of the flame are equally defined by

 exterior conditions2 they are imposed  
upon it by the shape of the burner and  
the pressure of the gas passing through 
it4 ,the form of the engine is as its   
designer has made it4 ,but the form of  
the living organism is imposed upon it  
from within2 and1 as far as we can tell1
 is inherent in it4 ,here is the wonder 
and mystery of life3 the power of the   
living organism to assimilate dead      
matter1 to give it life and bring it    
into the law and unity of the organism  
itself4 ,but it cannot do this          
indiscriminately2 it is not able thus to
 convert every dead material2 it is     
restricted1 narrowly restricted1 in its 
action4 ,one of the chief               
characteristics of living matter is     
found in the continuous range of        
chemical reactions which take place     
between living cells and their inorganic
 surroundings4 ,without cease certain   
substances are taken up and disappear in
 the endless round of chemical reactions
 in the cell4 ,other substances which   

have been produced by the chemical      
reactions in living matter pass out of  
the cell and reappear in inorganic      
nature as waste products of the life    
process4 ,the whole complex of these    
chemical transformations is generally   
called ,metabolism4 ,inorganic matter   
contrasts strikingly with living        
substance4 ,however long a crystal or a 
piece of metal is kept in observation1  
there is no change of the substance1 and
 the molecules remain the same and in   
the same number4 ,for living matter the 
continuous change of substances is an   
indispensable condition of existence4   
,to stop the supply of food material for
 a certain time is sufficient to cause a
 serious lesion of the life process or  
even the death of the cell4 ,but the    
same happens when we hinder the passing 
out of the products of chemical         
transformation from the cell4 ,on the   
other hand1 we may keep a crystal of    
lifeless matter in a glass tube         
carefully shut up from all exchange of  

substance with the external world for as
 many years as we like4 ,the existence  
of this crystal will continue without   
end and without change of any of its    
properties4 ,there is no known living   
organism which could remain in a dry    
resting state for an infinitely long    
period of time4 ,the longest lived are  
perhaps the spores of mosses which can  
exist in a dry state more than a hundred
 years4 ,as a rule the seeds of higher  
plants show their vital power already   
weakened after ten years2 most of them  
do not germinate if kept more than      
twenty to thirty years4 ,these          
experiences lead to the opinion that    
even dry seeds and spores of lower      
plants in their period of rest of       
vegetation continue the processes of    
metabolism to a certain degree4 ,this   
supposition is confirmed by the fact    
that a very slight respiration and      
production of carbonic acid can be      
proved when the seeds contain a small   
percentage of water4 ,it seems as if    

life were weakened in these plant organs
 to a quite imperceptible degree1 but   
never1 not even temporarily1 really     
suspended4  ,life is1 therefore1 quite  
inseparable from chemical reactions1 and
 on the whole what we call life is      
nothing else but a complex of           
innumerable chemical reactions in the   
living substance which we call          
protoplasm4#a  ,the essential quality1  
therefore1 of life is continual change1 
but not mere change in general4 ,it is  
that special process of the circulation 
of matter which we call metabolism1 and 
this circulation is always connected    
with a particular chemical              
substance--protoplasm4  ,in this        
substance five elements are always      
present and predominant--carbon1 oxygen1
 nitrogen1 hydrogen1 and sulphur4 ,the  
compounds which these five elements form
 with each other are most complex and   
varied1 and they also admit to          
combination--but in smaller             
proportions--some of the other elements1

 of which phosphorus1 potassium1        
calcium1 magnesium1 and iron are the    
most important4  ,for protoplasm--using 
the term in the most general sense--is a
 chemical substance1 not a mere mixture 
of a number of chemical elements1 nor a 
mere mechanical structure4 ,however     
differently the various plasma          
substances behave in detail1 they always
 exhibit the same general composition as
 the other albuminoids out of the five  
'organo-genetic elements'--namely in    
point of weight1 #ea-ed carbon1 #ba-bc  
oxygen1 #ae-ag nitrogen1 #f-g hydrogen1 
and #a-b sulphur4#b  ,haeckel1 the      
writer just quoted1 describes the plasm1
 the universal basis of all the vital   
phenomena1 in the following terms3 ,in  
every case where we have with great     
difficulty succeeded in examining the   
plasm as far as possible and separating 
it from the plasma-products1 it has the 
appearance of a colourless1 viscous     
substance1 the chief physical property  
of which is its peculiar thickness and  

consistency4 ,the physicist             
distinguishes three conditions of       
inorganic matter--solid1 fluid1 and     
gaseous4 ,active living protoplasm      
cannot be strictly described as either  
fluid or solid in the physical sense4   
,it presents an intermediate stage      
between the two which is best described 
as viscous2 it is best compared to a    
cold jelly1 or solution of glue4 ,just  
as we find the latter substance in all  
stages between the solid and the fluid1 
so we find in the case of protoplasm4   
,the cause of this softness is the      
quantity of water contained in the      
living matter1 which generally amounts  
to a half of its volume and weight4 ,the
 water is distributed between the plasma
 molecules or the ultimate particles of 
living matter in much the same way as it
 is in the crystals of salts1 but with  
the important difference that it is very
 variable in quantity in the plasm4 ,on 
this depends the capacity for the       
absorption or imbibition in the plasm1  

and the mobility of its molecules1 which
 is very important for the performance  
of the vital actions4 ,however1 this    
capacity of absorption has definite     
limits in each variety of plasm2 living 
plasm is not soluble in water1 but      
absolutely resists the penetration of   
any water beyond this limit4#c ,and     
,czapek further tells us that the most  
striking feature of cell life is the    
fact that an enormous number of chemical
 reactions take place within the        
narrowest space4 ,most plant cells do   
not exceed #j4a to #j4e millimetres in  
diameter4 ,their greatest volume        
therefore can only be an eighth of a    
cubic millimetre4 ,nevertheless1 in this
 minute space we notice in every stage  
of cell life a considerable number of   
chemical reactions which are carried on 
contemporaneously1 without one          
disturbing the other in the slightest   
degree4#d  ,it is clear if organic      
bodies were built up of chemical        
compounds of small complexity and great 

stability that this continuous range of 
chemical reactions1 this unceasing      
metabolism1 could not take place4 ,it is
 therefore a necessary condition for    
organic substances that they should be  
built up of chemical compounds that are 
most complex and unstable4 ,exactly     
those substances which are most         
important for life possess a very high  
molecular weight1 and consequently very 
large molecules1 in comparison with     
inorganic matter4 ,for example3         
egg-albumin is said to have the         
molecular weight of at least #ae1jjj1   
starch more than #cj1jjj1 whilst the    
molecular weight of hydrogen is #b1 of  
sulphuric acid and of potassium nitrate 
about #ajj1 and the molecular weight of 
the heaviest metal salts does not exceed
 about #cjj4e  ,to sum up3 the living   
organism1 whether it be a simple cell1  
or the ordered community of cells making
 up the perfect plant or animal1 is an  
entity1 a living individual1 wherein    
highly complex and unstable compounds   

are unceasingly undergoing chemical     
reactions1 a metabolism essentially     
associated with protoplasm4 ,but these  
complex compounds are1 nevertheless1    
formed by the combinations of but a few 
of the elements now known to us4  ,many 
writers on the subject of the           
habitability of other worlds1 from      
contemplating the rich and apparently   
limitless variety of the forms of life1 
and the diversity of the conditions     
under which they exist1 have been led to
 assume that the basis of life must     
itself also in like manner be infinitely
 broad and infinitely varied4 ,in this  
they are mistaken4 ,as we have seen1 the
 elements entering into the composition 
of organic bodies are1 in the main1 few 
in number4 ,the temperatures at which   
they can exist are likewise strictly    
limited4 ,but1 above all1 that          
circulation of matter which we call     
,life--the metabolism of vital          
processes--requires for its continuance 
the presence of one indispensable       

factor--,,water4  ,protoplasm itself1 as
 ,czapek puts it1 is practically an     
albumin sol2 that is to say1 it is a    
chemical substance of which the chief   
constituents are albuminous matter and  
water1 and the protoplasm can only take 
from without material dissolved in      
water2 it can only eject matter in the  
same way4 ,this osmosis is an           
indispensable condition in the vital    
process4 ,and the streaming of          
protoplasm1 its continual movement in   
the cell1 can only be carried on in     
water4  ,,water is the compound of      
oxygen and hydrogen in the proportion of
 two atoms of hydrogen to one of oxygen4
 ,it is familiar to us in three states3 
solid1 liquid1 and gaseous1 or ice1     
water1 and steam4 ,but it is only in the
 liquid state that water is available   
for carrying on the processes of life4  
,this fact limits the temperatures at   
which the organic functions can be      
carried on1 for water under terrestrial 
conditions is only liquid for a hundred 

degrees2 it freezes at #j deg4          
,centigrade1 it boils at #ajj deg4      
,centigrade4 ,necessarily1 our          
experiences are mostly confined within  
this range1 and therefore we are apt    
unconsciously to assume that this range 
is all the range that is possible1      
whereas it is but a very small fraction 
of the range conceivable1 and indeed    
existing1 in cosmical space4 ,in its    
liquid state water is a general solvent1
 and yet pure water is neutral in its   
qualities1 both characteristics being   
essential to its usefulness as a vehicle
 for the protoplasmic actions4          
,naturally1 this function of water as a 
solvent can only exist when water is in 
the liquid state2 solid water1 that is  
ice1 neither dissolves nor flows2 and   
water1 when heated to boiling point1    
passes into vapour1 and so leaves the   
organism moistureless1 and therefore    
dead4 ,it is possible to grind a living 
organism to a pulp so that the structure
 of the cells is practically destroyed1 

and yet for some reactions which are    
quite peculiar to life still to show    
themselves for some appreciable time4   
,but when the cell-pulp is heated to the
 temperature of boiling water1 these    
chemical processes cannot be longer     
observed4 ,what is left may then be     
considered as definitely dead4  ,water  
is1 then1 indispensable for the living  
organism2 but there are two great       
divisions of such organisms--plants and 
animals4 ,animals are generally1 but not
 universally1 free to move1 and         
therefore to travel to seek their food4 
,but their food is restricted2 they     
cannot directly convert inorganic matter
 to their own use2 they can only        
assimilate organic material4 ,the plant1
 on the other hand1 unlike the animal1  
can make use of inorganic material4     
,plant life1 therefore1 requires an     
abundant supply of water in which the   
various substances necessary for its    
support can be dissolved2 it must either
 be in water1 or1 if on land1 there must

 be an active circulation of water both 
through the atmosphere and through the  
soil1 so as to bring to it the food that
 it requires4 ,animal life presupposes  
plant life1 for it is always dependent  
upon it4  ,many writers have assumed    
that life is very widely distributed in 
connection with this planet4 ,the       
assumption is a mistaken one1 as has    
been well pointed out by ,garrett ,p4   
,serviss1 a charming writer on          
astronomical subjects3 ,on the ,earth we
 find animated existence confined to the
 surface of the crust of the globe1 to  
the lower and denser strata of the      
atmosphere1 and to the film of water    
that constitutes the oceans4 ,it does   
not exist in the heart of the rocks     
forming the body of the planet nor in   
the void of space surrounding it outside
 the atmosphere4 ,as the ,earth         
condensed from the original nebula1 and 
cooled and solidified1 a certain        
quantity of matter remained at its      
surface in the form of free gases and   

unstable compounds1 and1 within the     
narrow precincts where these things     
were1 lying like a thin shell between   
the huge inert globe of permanently     
combined elements below1 and the equally
 unchanging realm of the ether above1   
life1 a phenomenon depending upon       
ceaseless changes1 combinations and     
re-combinations of chemical elements in 
unstable and temporary union1 made its  
appearance1 and there only we find it at
 the present time4#f  ,the huge inert   
globe of permanently combined elements  
below1 and the equally unchanging realm 
of the ether above1 offer no home for   
the living organism2 least of all for   
the highest of such organisms--,man4    
,both must be tempered to a condition   
which will permit and favour continual  
change1 the metabolism which is the     
essential feature of life4  ,when the   
earth had to be prepared for the        
habitation of man1 a veil1 as it were1  
of intermediate being was spread between
 him and its darkness1 in which were    

joined1 in a subdued measure1 the       
stability and the insensibility of the  
earth1 and the passion and perishing of 
mankind4  ,but the heavens1 also1 had to
 be prepared for his habitation4        
,between their burning light1--their    
deep vacuity1 and man1 as between the   
earth's gloom of iron substance1 and    
man1 a veil had to be spread of         
intermediate being2--which should       
appease the unendurable glory to the    
level of human feebleness1 and sign the 
changeless motion of the heavens with   
the semblance of human vicissitude4     
,between the earth and man arose the    
leaf4 ,between the heaven and man came  
the cloud4 ,his life being partly as the
 falling leaf and partly as the flying  
vapour4#g  ,the leaf and the cloud are  
the signs of a habitable world4 ,the    
leaf--that is to say1 plant life1       
vegetation--is necessary because animal 
life is not capable of building itself  
up from inorganic material4 ,this step  
must have been previously taken by the  

plant4 ,the cloud1 that is to say       
water-vapour1 is necessary because the  
plant in its turn cannot directly       
assimilate to itself the nitrogen from  
the atmosphere4 ,the food for the plant 
is brought to it by water1 and it       
assimilates it by the help of water4 ,it
 is1 therefore1 upon the question of the
 presence of water that the question of 
the habitability of a given world       
chiefly turns4 ,in the physical sense1  
man is born of water1 and any world     
fitted for his habitation must stand out
 of the water and in the water4         
,,chapter ,,iii  ,,the ,,sun   ,the ,sun
 is1 of all the heavenly bodies1 the    
most impressive1 and has necessarily1 at
 all times1 attracted the chief         
attention of men4 ,there are only two of
 the heavenly bodies that appear to be  
more than points of light1 only two that
 show a surface to the naked eye1 and   
the ,sun1 being so much the brighter of 
the two1 and the obvious source of all  
our light and heat1 and the fosterer of 

vegetation1 readily takes the premier   
place in interest4 ,in the present day  
we know too much about the ,sun for     
anyone to suppose that it can be the    
home of organic life2 but it is not many
 years since its habitability was       
seriously suggested even by so high an  
authority as ,sir ,william ,herschel4   
,he conceived that it was possible that 
its stores of light and heat might be   
confined to a relatively thin shell in  
its upper atmosphere1 and that below    
this shell a screen of clouds might so  
check radiation downward that it would  
be possible for an inner nucleus to     
exist which should be cool and solid4   
,this fancied inner globe would then    
necessarily enjoy perpetual daylight1   
and a climate which knew no variation   
from pole to pole4 ,to its inhabitants  
the entire heavens would be generally   
luminous1 the light not being           
concentrated into any one part of the   
vault2 and it was supposed that1        
ignorant of time1 a happy race might    

flourish1 cultivating the far-spread    
solar fields1 in perpetual daylight1 and
 in the serenity of a perpetual spring  
that was distracted by no storm4  ,the  
picture thus conjured up is a pleasing  
one1 though probably1 to the restless   
sons of ,earth1 it would seem to suffer 
somewhat from monotony4 ,but we now know
 that it corresponds in not a single    
detail to the actual facts4 ,the study  
of solar conditions carried on through  
the last hundred years has revealed to  
us1 not serenity and peace1 but storm1  
stress1 and commotion on the most       
gigantic scale4 ,but though we now can  
dismiss from our minds the possibility  
that the ,sun can be inhabited1 yet it  
is of such importance to the maintenance
 of life on this planet1 and by parity  
of reasoning to life on any other       
planet1 that a review of its conditions 
forms a necessary introduction to our   
subject4 ,further1 those conditions     
themselves will bring out certain       
principles that are of necessary        

application when we come to consider the
 case of particular planets4  ,the      
distance of the ,sun from the ,earth is 
often spoken of as the astronomical     
unit2 it is the fundamental measure of  
astronomy1 and all our information as to
 the sizes and distances of the various 
planets rests upon it4 ,and1 as we shall
 shortly see1 the particular problem    
with which we are engaged--the          
habitability of worlds--is directly     
connected with these two factors3 the   
size of the world in question1 and its  
distance from the ,sun4  ,the distance  
of the ,sun has been determined by      
several different methods the principles
 of which do not concern us here1 but   
they agree in giving the mean distance  
of the ,sun as a little less than       
#ic1jjj1jjj miles2 that is to say1 it   
would require #aa1gbj worlds as large as
 our own to be put side by side in order
 to bridge the chasm between the two4   
,or a traveller going round the ,earth  
at its equator would have to repeat the 

journey #cgcj times before he had       
traversed a space equal to the ,sun's   
distance4  ,but knowing the ,sun's      
distance1 we are able to deduce its     
actual diameter1 its superficial extent1
 and its volume1 for its apparent       
diameter can readily be measured4 ,its  
actual diameter then comes out as       
#hff1djj miles1 or #aji4d times that of 
the ,earth4 ,its surface exceeds that of
 the ,earth #aa1igj times2 its volume1  
#a1caj1jjj times4  ,but the weight of   
the ,sun is known as well as its size2  
this follows as a consequence of        
gravitation4 ,for the planets move in   
orbits under the influence of the ,sun's
 attraction2 the dimensions of their    
orbits are known1 and the times taken in
 describing them2 the amount of the     
attractive force therefore is also      
known1 that is to say1 the mass of the  
,sun4 ,this is #ccb1jjj times the mass  
of the ,earth2 and as the latter has    
been determined as equal to about       
#f1jjj1jjj1jjj1jjj1jjj1jjj1jjj tons     

that of the ,sun would be equal to      
#b1jjj1jjj1jjj1jjj1jjj1jjj1jjj1jjj1jjj  
tons4  ,it will be seen that the        
proportion of the volume of the ,sun to 
that of the ,earth is greater than the  
proportion of its mass to the ,earth's  
mass--almost exactly four times greater2
 so that the mean density of the ,sun   
can be only one-fourth that of the      
,earth4 ,yet1 if we calculate the force 
of gravity at the surfaces of both ,sun 
and ,earth1 we find that the ,sun has a 
great preponderance4 ,its mass is       
#ccb1jjj times that of the ,earth1 but  
to compare it with the attraction of the
 ,earth's surface we must divide by     
7#aji4d7b1 since the distance of the    
,sun's centre from its surface is #aji4d
 times as great as the corresponding    
distance in the case of the ,earth1 and 
the force of gravity diminishes as the  
square of the increased distance4 ,this 
gives the force of gravity at the solar 
surface as #bg4fe times its power at the
 surface of the ,earth1 so that a body  

weighing one ton here would weigh #bg   
tons #ac cwt4 if it were taken to the   
,sun4#h  ,this relation is one of great 
importance when we realize that the     
pressure of the ,earth's atmosphere is  
#ad4g lb4 on the square inch at the sea 
level2 that is to say1 if we could take 
a column of air one square inch in      
section1 extending from the surface of  
the ,earth upwards to the very limit of 
the atmosphere1 we should find that it  
would have this weight4 ,if we construct
 a water barometer1 the column of water 
required to balance the atmosphere must 
be #cd feet high1 while the height of   
the column of mercury in a mercurial    
barometer is #cj inches high1 for the   
weight of #cj cubic inches of mercury or
 of #djh cubic inches of water 7#cd x   
#ab  #djh7 is #ad4g lb4  ,if1 now1 we   
ascend a mountain1 carrying a mercurial 
barometer with us we should find that it
 would fall about one inch for the first
 #ijj feet of our ascent2 that is to    
say1 we should have left one-thirtieth  

of the atmosphere below us by ascending 
#ijj feet4 ,as we went up higher we     
should find that we should have to climb
 more than #ijj feet further in order   
that the barometer might fall another   
inch2 and each successive inch1 as we   
went upward1 would mean a longer climb4 
,at the height of #bgfj feet the        
barometer would have fallen three       
inches2 we should have passed through   
one-tenth of the atmosphere4 ,at the    
height of #ehjj feet1 we should have    
passed through one-fifth of the         
atmosphere1 the barometer would have    
dropped six inches2 and so on1 until at 
about three and a third miles above sea 
level the barometer would read fifteen  
inches1 showing that we had passed      
through half the atmosphere4 ,mont      
,blanc is not quite three miles high1 so
 that in ,europe we cannot climb to the 
height where half the atmosphere is left
 below us1 and there is no terrestrial  
mountain anywhere which would enable us 
to double the climb2 that is to say1 to 

ascend six and two-third miles4 ,could  
we do so1 however1 we should find that  
the barometer had fallen to seven and a 
half inches2 that the second ascent of  
three and a third miles had brought us  
through half the remaining atmosphere1  
so that only one-fourth still remained  
above us4 ,in the celebrated balloon    
ascent made by ,mr4 ,coxwell and ,mr4   
,glaisher on ,september #e1 #ahfa1 an   
even greater height was attained1 and it
 was estimated that the barometer fell  
at its lowest reading to seven inches1  
which would correspond to a height of   
#ci1jjj feet4  ,but on the ,sun1 where  
the force of gravity is #bg4fe times as 
great as at the surface of the ,earth1  
it would1 if all the other conditions   
were similar1 only be necessary to      
ascend one furlong1 instead of three and
 a third miles1 in order to reach the   
level of half the surface pressure1 and 
an ascent of two furlongs would bring us
 to the level of quarter pressure1 and  
so on4 ,if then the solar atmosphere    

extends inwards1 below the apparent     
surface1 it should approximately double 
in density with each furlong of descent4
 ,these considerations1 if taken alone1 
would point to a mean density of the    
,sun not as we know it to be1 less than 
that of the ,earth1 but immeasurably    
greater2 but the discordance is         
sufficiently explained when we come to  
another class of facts4  ,these relate  
to the temperature of the ,sun1 and to  
the enormous amount of light and heat   
which it radiates forth continually4    
,this entirely transcends our power to  
understand or appreciate4 ,nevertheless1
 the astonishing figures which the best 
authorities give us may1 by their       
vastness1 convey some rough general     
impression that may be of service4 ,thus
 ,prof4 ,c4 ,a4 ,young puts the total   
quantity of sunlight as equivalent to   
#a1ege1jjj1jjj1jjj1jjj1jjj1jjj1jjj1jjj  
standard candles4  ,the intensity of    
sunlight at each point of the ,sun's    
surface is variously expressed as       

#aij1jjj times that of a standard       
candle1   #ecjj times that of the metal 
in a ,bessemer converter1   #adf times  
that of a calcium light1   or1 #c4d     
times that of an electric arc4  ,the    
same authority estimates at #cj calories
 the value of the ,solar ,constant2 that
 is to say1 the heat which1 if our      
atmosphere were removed1 would be       
received from the ,sun in a minute of   
time upon a square metre of the ,earth's
 surface that had the ,sun in its       
zenith1 would be sufficient to raise the
 temperature of a kilogram of water #cj 
degrees ,centigrade4 ,this would involve
 that the heat radiation from each      
square metre of the ,sun's surface would
 equal #a1cdj1jjj calories2 or          
sufficient to melt through in each      
minute of time a shell of ice           
surrounding the ,sun to the thickness of
 #eh4b feet4 ,prof4 ,abbot's most recent
 determination of the solar constant    
diminishes these estimates by one third2
 but he still gives the probable        

temperature of the solar surface as not 
far short of #gjjj degrees ,centigrade1 
or about #ab1jjj degrees ,fahrenheit4   
,the ,sun1 then1 presents us with       
temperatures and pressures which        
entirely surpass our experience on the  
,earth4 ,the temperatures1 on the one   
hand1 are sufficient to convert into a  
permanent gas every substance with which
 we are acquainted2 the pressures1 on   
the other hand1 apart from the high     
temperatures1 would probably solidify   
every element1 and the ,sun1 as a whole1
 would present itself to us as a        
comparatively small solid globe1 with a 
density like that of platinum4 ,with    
both factors in operation1 we have the  
result already given3 a huge globe1 more
 than one hundred times the diameter of 
the ,earth1 yet only one-fourth its     
density1 and gaseous probably throughout
 the whole of its enormous bulk4  ,what 
effect have these two factors1 so       
stupendous in scale1 upon its visible   
surface8 ,what is the appearance of the 

,sun8  ,it appears to be a large glowing
 disc1 sensibly circular in outline1    
with its edge fairly well-defined both  
as seen in the telescope and as         
registered on photographs4 ,in the      
spectroscope1 or when in an eclipse of  
the ,sun the ,moon covers the whole     
disc1 a narrow serrated ring is seen    
surrounding the rim1 like a velvet pile 
of a bright rose colour4 ,this crimson  
rim1 the sierra or chromosphere as it is
 usually called1 is always to be found  
edging the entire ,sun1 and therefore   
must carpet the surface everywhere4 ,but
 under ordinary conditions1 we do not   
see the chromosphere itself1 but look   
down through it on the photosphere1 or  
general radiating surface4 ,this1 to the
 eye1 certainly looks like a definite   
shell1 but some theorists have been so  
impressed with the difficulty of        
conceiving that a gaseous body like the 
,sun could1 under the conditions of such
 stupendous temperatures as there exist1
 have any defined limit at all1 that    

they deny that what we see on the ,sun  
is a real boundary1 and argue that it   
only appears so to us through the       
effects of the anomalous refraction or  
dispersion of light4 ,such theories     
introduce difficulties greater and more 
numerous than those that they clear     
away1 and they are not generally        
accepted by practical observers of the  
,sun4 ,they seem incompatible with the  
apparent structure of the photosphere1  
which is everywhere made up of a        
complicated mottling3 minute grains     
somewhat resembling those of rice in    
shape1 of intense brightness1 and       
irregularly scattered4 ,this mottling is
 sometimes coarsely1 sometimes finely   
textured2 in some regions it is sharp   
and well defined1 in others misty or    
blurred1 and in both cases they are     
often arranged in large elaborate       
patterns1 the figures of the pattern    
sometimes extending for a hundred       
thousand miles or more in any direction4
 ,the rice-like grains or granules of   

which these figures are built up1 and   
the darker pores between them1 are1 on  
the other hand1 comparatively small1 and
 do not1 on the average1 exceed two to  
four hundred miles in diameter4  ,but   
the ,sun shows us other objects of quite
 a different order in their dimensions4 
,here and there the bright granules of  
the photosphere become disturbed and    
torn apart1 and broad areas are exposed 
which are relatively dark4 ,these are   
sunspots1 and in the early stages of    
their development they are usually      
arranged in groups which tend to be     
stretched out parallel to the ,sun's    
equator4 ,a group of spots in its later 
stages of development is more commonly  
reduced to a single round1 well-defined1
 dark spot4 ,these groups1 when near the
 edge of the ,sun1 are usually seen to  
be accompanied by very bright markings1 
arranged in long irregular lines1 like  
the foam on an incoming tide4 ,these    
markings are known as the faculae1 from 
their brightness4 ,in the spectroscope1 

when the serrated edges of the          
chromosphere are under observation1     
every now and then great prominences1 or
 tongues and clouds of flame1 are seen  
to rise up from them1 sometimes changing
 their form and appearance so rapidly   
that the motion can almost be followed  
by the eye4 ,an interval of fifteen or  
twenty minutes has frequently been      
sufficient to transform1 quite beyond   
recognition1 a mass of flame fifty      
thousand miles in height4 ,sometimes a  
prominence of these1 or even greater1   
dimensions has formed1 developed1 risen 
to a great distance from the ,sun1 and  
completely disappeared within less than 
half an hour4 ,the velocity of the gas  
streams in such eruptions often exceeds 
one hundred miles a second2 sometimes1  
though only rarely1 it reaches a speed  
twice as great4  ,sunspots do not offer 
us examples of motions of this order of 
rapidity1 but the areas which they      
affect are not less astonishing4 ,many  
spot groups have been seen to extend    

over a length of one hundred thousand1  
or one hundred and fifty thousand miles1
 and to cover a total area of a thousand
 million square miles4 ,indeed1 the     
great group of ,february1 #aije1 at its 
greatest extent1 covered an area four   
times as great as this4 ,again1 in the  
normal course of the development of a   
spot group1 the different members of the
 group frequently show a kind of        
repulsion for each other in the early   
stages of the group's history1 and the  
usual speed with which they move away   
from each other is three hundred miles  
an hour4  ,the spots1 the faculae1 the  
prominences1 are all1 in different ways1
 of the nature of storms in an          
atmosphere2 that is to say1 that1 in the
 great gaseous bulk of the ,sun1 certain
 local differences of constitution1     
temperature1 and pressure are marked by 
these different phenomena4 ,from this   
point of view it is most significant    
that many spots are known to last for   
more than a month2 some have been known 

to endure for even half a year4 ,the    
nearest analogy which the ,earth        
supplies to these disturbances may be   
found in tropical cyclones1 but these   
are relatively of far smaller area1 and 
only last a few days at the utmost1     
while a hundred miles an hour is the    
greatest velocity they ever exhibit1 and
 this1 fortunately1 only under          
exceptional circumstances4 ,for a wind  
of such violence mows down buildings and
 trees as a scythe the blades of grass2 
and were tornadoes moving at a rate of  
#cjj miles an hour as common upon the   
,earth as spots are upon the ,sun1 it   
would be stripped bare of plants and    
animals1 as well as of men and of all   
their works4  ,it is not an accident    
that the ,sun1 when storm-swept1 shows  
this violence of commotion1 but a       
necessary consequence of its enormous   
temperature and pressures4 ,as we have  
seen1 the force of gravity at its       
surface is #bg4fe times that at the     
surface of the ,earth1 where a body     

falls #af4a feet in the first second of 
time2 on the ,sun1 therefore1 a body    
would fall #dde feet in the first       
second2 and the atmospheric motions     
generally would be accelerated in the   
same proportion4  ,the high             
temperatures1 the great pressures1 the  
violent commotions which prevail on the 
,sun are1 therefore1 the direct         
consequence of its enormous mass4 ,the  
,sun is1 then1 not merely the type and  
example of the chief source of light and
 heat in a given planetary system2 it   
indicates to us that size and mass are  
the primary tokens by which we may judge
 the temperature of a world1 and the    
activity to be expected in its changes4 
,,chapter ,,iv  ,,the ,,distribution    
,,of ,,the ,,elements ,,in ,,space   ,it
 is now an old story1 but still         
possessing its interest1 how ,fraunhofer
 analysed the light of the ,sun by      
making it pass through a narrow slit and
 a prism1 and found that the broad      
rainbow-tinted band of light so obtained

 was interrupted by hundreds of narrow  
dark lines1 images in negative of the   
slit2 and how ,kirchhoff succeeded in   
proving that two of these dark lines    
were caused by the white light of the   
solar photosphere having suffered       
absorption at the ,sun by passing       
through a stratum of glowing sodium     
vapour4 ,from that time forward it has  
been known that the ,sun is surrounded  
by an atmosphere of intensely heated    
gases1 among which figure many of those 
elements familiar to us in the solid    
form on the ,earth1 such as iron1       
cobalt1 nickel1 copper1 manganese1 and  
the like4 ,these metals1 here the very  
types of solid bodies1 are permanent    
gases on the ,sun4  ,the ,sun1 then1 is 
in an essentially gaseous condition1    
enclosed by the luminous shell which we 
term the photosphere4 ,this shell ,prof4
 ,c4 ,a4 ,young and the majority of     
astronomers regard as consisting of a   
relatively thin layer of glowing clouds1
 justifying the quaint conceit of ,r4   

,a4 ,proctor1 who spoke of the ,sun as a
 ,bubble2 that is1 a globe of gas       
surrounded by an envelope so thin in    
comparison as to be a mere film4 ,there 
has been much difference of opinion as  
to the substance forming these clouds1  
but the theory is still widely held     
which was first put forward by ,dr4     
,johnstone ,stoney in #ahfg1 that they  
are due to the condensation of carbon1  
the most refractory of all known        
elements4 ,prof4 ,abbot1 however1       
refuses to believe in a surface of this 
nature1 holding that the temperature of 
the ,sun is too high even at the surface
 to permit any such condensation4  ,the 
application of the spectroscope to      
astronomy is not confined to the ,sun1  
but reaches much further4 ,the stars    
also yield their spectra1 and we are    
compelled to recognize that they also   
are suns2 intensely heated globes of    
glowing gas1 rich in the same elements  
as those familiar to us on the ,earth   
and known by their spectral lines to be 

present on the ,sun4 ,the stars1        
therefore1 cannot themselves be         
inhabited worlds any more than the ,sun1
 and at a stroke the whole of the       
celestial luminaries within the furthest
 range of our most powerful telescopes  
are removed from our present search4    
,only those members of our solar system 
that shine by reflecting the light of   
the ,sun can be cool enough for         
habitation2 the true stars cannot be    
inhabited1 for1 whatever their quality  
and order1 they are all suns1 and must  
necessarily be in far too highly heated 
a condition to be the abode of life4    
,many of them may1 perhaps1 be a source 
of light and heat to attendant planets1 
but there is no single instance in which
 such a planet has been directly        
observed2 no dark1 non-luminous body has
 ever been actually seen in attendance  
on a star4 ,many double or multiple     
stars are known1 but these are all      
instances in which one sun-like body is 
revolving round another of the same     

order4#i ,we see no body shining by     
reflected light outside the limits of   
the solar system4 ,planets to the       
various stars may exist in countless    
numbers1 but they are invisible to us1  
and we cannot discuss conditions where  
everything is unknown4 ,enquiry in such 
a case is useless1 and speculation vain4
  ,the stars1 as revealed to us by the  
spectroscope are all of the same order  
as the ,sun1 but they are not all of the
 same species4 ,quite a large number of 
stars1 of which ,arcturus is one of the 
best-known examples1 show spectra that  
are essentially the same as that of the 
,sun1 but there are other stars of which
 the spectra bear little or no semblance
 to it4 ,nevertheless1 it remains true  
that1 on the whole1 stellar spectra bear
 witness to the presence of just the    
same elements as we recognize in the    
,sun1 though not always in the same     
proportions or in the same              
conditions--hydrogen1 calcium1 sodium1  
magnesium1 iron1 titanium1 and many more

 are recognized in nearly all4 ,it is   
true that not all the known terrestrial 
elements have yet been identified in    
either ,sun or stars2 but1 in general1  
those missing are either negative       
elements like the halogens1 or elements 
of great atomic weight like mercury and 
platinum4 ,that elements of one class   
should1 as a rule1 reveal their presence
 in ,sun and stars wherever these are   
placed1 and1 correspondingly1 that other
 classes should as generally fail to    
show themselves1 indicate that such     
absence is more likely to be due to the 
general structure of the stellar        
photospheres and reversing layers than  
to any irregularity in the distribution 
of matter in the universe4 ,it is easy1 
for example1 to conceive that the heavy 
metals may lie somewhat deeper down     
within the ,sun or star than those of   
low atomic weight4 ,in the case of the  
,sun1 there seems a clear connection    
between atomic weight and the           
distinctness with which the element is  

recognized in the spectrum of the       
photosphere1 the lower atomic weights   
showing themselves more conspicuously4  
,it is clear that not all elements      
present in a ,sun or star show          
themselves in its spectrum4 ,oxygen is  
very feebly represented by its elemental
 lines1 but the flutings of titanium    
oxide are found in sunspots1 and with   
great distinctness in a certain type of 
stars4 ,nitrogen1 too1 though not       
directly recognized1 proves its presence
 by the lines of cyanogen4 ,the case of 
helium is one of particular interest2   
this element was recognized by a very   
bright yellow line in the solar         
prominences before it was known to exist
 on the ,earth2 indeed1 it received the 
name helium because it then seemed to be
 a purely solar constituent4 ,now it is 
seen as a strong absorption line in the 
spectrum of many stars2 but for some    
reason it is not in general seen as an  
absorption line over the ,sun's disc1   
and if our ,sun were removed to such    

distance so as to appear to us only as a
 star1 we should have no evidence that  
it contained any helium at all4 ,so far1
 then1 as the evidence of the           
spectroscope goes1 the elements present 
in the ,earth are present throughout the
 whole extent of the universe within our
 view3 the same elements and with the   
same qualities4 ,for the lines of the   
spectrum of an element are the          
revelation of its innermost molecular   
structure1 so that we can confidently   
affirm that hydrogen and oxygen on      
,sirius1 ,arcturus1 or the ,sun1 are    
essentially the same elements as        
hydrogen and oxygen on the ,earth4 ,on a
 planet attached to any of these stars1 
the two gases would combine together to 
form water under just the same          
conditions as they do here on the       
,earth2 and at suitable temperatures    
that water would be a neutral liquid1   
capable of dissolving just the same     
chemical substances that it does here4  
,it would freeze as it does here2 it    

would evaporate as it does here2 it     
would be water as completely in all its 
qualities and conditions as earthly     
water is4 ,and what applies to one      
element or compound applies to all4     
,throughout the whole extent of space1  
the same building materials have been   
employed1 and throughout they retain the
 same qualities4  ,hydrogen is seen in  
the spectra of nearly all stars1 and    
also in those of nebulae4 ,the elemental
 lines of oxygen are not indeed seen in 
stellar spectra1 but that the element is
 present is shown by the flutings of    
titanium oxide which distinguish stars  
like ,antares4 ,nitrogen and carbon     
again are not recognized by their       
elemental lines1 but the lines of       
cyanogen are seen in the spectra of     
comets and of sunspots1 and hydrocarbon 
flutings in the spectra of comets and   
red stars2 while in a few of the hottest
 stars even sulphur has recently been   
identified4#aj ,all the five            
organo-genetic elements are therefore   

abundantly diffused through space2 the  
materials for protoplasm1 the albuminous
 substance with water1 are at hand      
everywhere4 ,this being so1 it is       
reasonable to infer that if organic life
 exists elsewhere than on this ,earth1  
its essential feature1 there as here1 is
 the metabolism of nitrogenous carbon   
compounds in association with           
protoplasm4  ,but it is objected that we
 are not yet able to identify all the   
lines in solar or stellar spectra2 may  
not some of these lines be due to       
elements of which we know nothing here1 
and may not such new elements form      
complex and unstable compounds with each
 other1 or with some of those familiar  
to us1 that would take the place of the 
five organo-generators1 and so give rise
 to a physical basis of life1 different 
from that we know on this ,earth8  ,but 
the development of ,mendeleeff's        
,periodic ,law has shown that the       
elements are not to be regarded as      
disconnected entities4 ,the ,law as     

given in ,mendeleeff's own words1 runs3 
,the properties of the elements as well 
as the forms and properties of their    
compounds are in periodic dependence on1
 or 7expressing ourselves algebraically7
 form a periodic function of the atomic 
weights of the elements4 ,in other      
words1 they form a series1 not only as  
it regards their atomic weights1 but    
also as it regards their own properties 
and the forms and properties of their   
compounds4 ,we are no longer at liberty1
 as we might have been many years ago1  
to call into fancied existence new      
elements having no relation in their    
properties and compounds to those with  
which we are acquainted4 ,new elements1 
no doubt1 will be discovered in the     
future1 as in the past2 and indeed we   
may be able to discover them and learn  
their atomic weights and properties     
without ever being able to handle them  
in a terrestrial laboratory4  ,in a     
series of remarkable papers communicated
 to the ,royal ,astronomical ,society   

during the past year 7#aiaa-aiab71 ,dr4 
,j4 ,w4 ,nicholson has given the result 
of his computation of the positions of  
the spectral lines of two elements of   
simple structure1 and has found that the
 resulting lines correspond1 for one    
dynamical system1 to the chief          
unidentified lines observed in the      
spectra of nebulae1 and for the other1  
to the chief unidentified lines in the  
spectrum of the corona4 ,the latter     
element is probably associated with the 
halogens1 but of much lower atomic      
weight 7namely1 #a4c71 than fluorine2 he
 therefore gives it the name of         
,protofluorine4 ,the other element1 to  
which he gives the name ,nebulium1 will 
have an atomic weight of #b4a4 ,prof4   
,max ,wolf1 of ,heidelberg1 has recently
 pointed out#aa the evidence of the     
presence of two other unknown gases in  
the ,ring nebula in ,lyra1 and there is 
no reason to suppose that the process of
 discovery has come to an end4 ,but we  
cannot imagine that we shall discover   

any new elements that are more abundant 
and more universally diffused than the  
five which give us protoplasm--the      
physical basis of life4 ,to take an     
analogy from the solar system3 many     
hundreds of planetoids have now been    
discovered between the orbits of ,mars  
and ,jupiter1 and probably many hundreds
 more remain to be discovered2 but of   
one thing we are certain1 that none of  
the planetoids yet to be discovered will
 be of the same rank as either of those 
two guardians1 ,mars and ,jupiter1 who  
revolve on the confines of the          
planetoidal zone4 ,indeed1 ,ceres1 the  
planetoid first discovered1 has a       
greater mass than the aggregate of all  
discovered since1 and probably of all   
that exist in the zone4  ,water is      
essential for life here1 but the quality
 in water which restricts the range of  
terrestrial life is that it freezes at  
#j deg4 ,centigrade1 and boils at #ajj  
deg4 ,centigrade2 it is only in the     
liquid state during the intermediate    

range of #ajj degrees4 ,in order to     
extend the range for living organisms1  
we should have1 therefore1 to discover a
 new vehicle1 that1 possessing all the  
other qualities of water1 is not        
restricted to the liquid state within   
the same limits4 ,but we are at once met
 with the difficulty that the first     
essential for the vehicle is that it    
should be abundant1 and there are no    
other elements more abundant than       
hydrogen and oxygen4 ,this new vehicle  
must1 like water1 be both neutral and   
stable1 or it would itself interfere    
with the highly unstable compounds that 
are a necessity for metabolism4 ,and1 if
 we could find this new vehicle1 liquid 
at temperatures outside the #j deg4 to  
#ajj deg4 ,centigrade1 have we any      
reason to suppose that protoplasm itself
 would be able to endure these outlying 
temperatures8 ,looking through the range
 of substances available1 we can only   
say that none other presents itself as  
approaching water in suitability for its

 essential office4 ,if we1 ourselves1   
were able to create a vehicle1 could we 
imagine one more perfectly suited8      
,,chapter ,v  ,,the ,,moon   ,the ,sun  
and ,moon offer to our sight almost     
exactly the same apparent diameters2 to 
the eye1 they look the same size4 ,but  
as we know the ,sun to be #djj times as 
distant as the ,moon1 it is necessarily 
#djj times as large2 its surface must   
exceed that of the ,moon by the square  
of #djj1 or #afj1jjj2 its volume by the 
cube of #djj1 or #fd1jjj1jjj4 ,as the   
,sun is of low mean density1 its mass   
does not exceed that of the ,moon in    
quite the same high ratio2 but it is    
equal in mass to    #bg1jjj1jjj moons4  
,compared with the ,sun1 the ,moon is   
therefore an insignificant little       
ball--a mere particle2 but as a world   
for habitation it possesses some        
advantages over the ,sun4 ,the first    
glance at it in a telescope is          
sufficient to assure the observer that  
he is looking at a solid1 substantial   

globe4 ,it is not only substantial1 it  
is rugged2 its surface is broken up into
 mountains1 hills1 valleys1 and plains2 
the mountains stand out in sensible     
relief2 it looks like a ball of solid   
silver boldly embossed and chased4  ,so 
far all is to the good for the purpose  
of habitation4 ,wherever men are1 they  
must have a solid platform on which to  
stand2 they must have a stable terrene  
whereon their food may grow1 and this   
the ,moon could supply4 ,the ,earth's   
gloom of iron substance is necessary for
 man here1 and the ,moon appears to     
offer a like stability4  ,another       
favourable condition is that we know    
that the ,moon receives from the ,sun a 
sufficient supply of light and heat4    
,each square yard of its surface        
receives1 on the average1 the same      
amount of light and heat that would fall
 upon a square yard on the ,earth that  
was presented towards the ,sun at the   
same inclination2 and we know from our  
own experience that this is sufficient  

for the maintenance of life4  ,and the  
,moon is near enough for us to subject  
her to a searching scrutiny4 ,every part
 of the hemisphere turned toward us has 
been repeatedly examined1 measured1 and 
photographed2 to that extent our        
knowledge of its topography is more     
complete than of the world on which we  
live4 ,there are no unexplored regions  
on our side of the ,moon4 ,the great    
photographs taken in recent years at the
 observatories of ,paris and of the     
,university of ,chicago have shown      
thousands of crater-pits1 not more than 
a mile across2 and narrow lines on the  
,moon's surface have been detected with 
a breadth less than one-tenth of this4  
,an elevation on the ,moon1 if it rose  
up abruptly from an open plain1 would   
make its presence apparent by the shadow
 which it would cast soon after sunrise 
or near sunset2 in this way an isolated 
building1 if it were as large as the    
great pyramid of ,ghizeh1 would also    
show itself1 and all our great towns and

 cities would be apparent as areas of   
indistinct mottling1 though the details 
of the cities would not be made out4    
,but if vegetation took the same forms  
on the ,moon as on the ,earth1 and      
passed through the same changes1 we     
should have no difficulty in perceiving 
the evidence of its presence4 ,if we    
were transported to the ,moon and turned
 our eyes earthward1 we should not need 
the assistance of any telescope in order
 to detect terrestrial changes which    
would be plainly connected with the     
seasonal changes of vegetation4 ,the    
,earth would present to us a disc four  
times the apparent diameter of the      
,moon1 and on that disc ,canada would   
offer as great an area as the whole of  
the ,moon does to us4 ,we could easily  
follow with the naked eye the change    
from the glittering whiteness of the    
aspect of ,canada when snow-covered in  
winter1 to the brown1 green and gold    
which would succeed each other during   
the brighter months of the year4 ,and   

this type of change would alternate     
between the northern and southern       
hemispheres1 for the winter of ,canada  
is the summer of the ,argentine1 and    
conversely4  ,we ought1 therefore1 to   
have no difficulty in observing seasonal
 changes on the ,moon1 if such take     
place4 ,but nothing of the kind has ever
 been remarked2 no changes sufficiently 
pronounced for us to be sure of them are
 ever witnessed4 ,here and there some   
slight mutations have been suspected1   
nearly all accomplishing their cycle in 
the course of a lunar day2 so that it is
 difficult to separate them from changes
 purely apparent1 brought about by the  
change in the incidence of the          
illumination4  ,the difference in       
appearance of a given area on the ,moon 
when viewed under a low ,sun and when   
the ,sun is on the meridian is very     
striking4 ,in the first case everything 
is in the boldest relief2 the shadows   
are long and intensely black2 the whole 
area under examination in the telescope 

seems as if it might be handled4 ,under 
the high ,sun1 the contrasts are gone2  
the scenery appears flat1 many of the   
large conspicuous markings are only     
recognized with difficulty4 ,thus the   
terse remark of ,maedler1 ,the full     
,moon knows no ,maginus1 has become a   
proverb amongst selenographers2 yet     
,maginus is a fine walled plain some    
eighty miles in diameter1 and its       
rampart attains a height in parts of    
#ad1jjj feet4 ,maginus lies near ,tycho1
 which has been well named the lunar    
metropolis1 for from it radiates the    
principal system of bright streaks      
conspicuous on the full ,moon4 ,these   
white streaks appear when the shadows   
have vanished or are growing short2 they
 are not seen under a low ,sun4  ,the   
changes which appear to take place in   
the lunar formations owing to the change
 in their illumination are much more    
striking and varied than would be       
anticipated4 ,but the question arises   
whether all the changes that are        

associated with the progress of the     
lunar day can be ascribed to this       
effect4 ,thus1 ,prof4 ,w4 ,h4 ,pickering
 writes concerning a well-known pair of 
little craters of about nine miles in   
diameter1 known as ,messier and ,messier
 ,a1 situated side by side not far from 
the centre of the ,mare ,fecunditatis4  
,when the ,sun rises first on them1 the 
eastern one1 ,a1 is triangular and      
larger than ,messier1 which latter is   
somewhat pear-shaped4 ,about three days 
after sunrise they both suddenly turn   
white1 ,messier rapidly grows in size1  
soon surpasses ,a1 and also becomes     
triangular in shape4 ,six days after    
sunrise the craters are again nearly of 
the same size1 owing to the diminution  
of ,messier4 ,the shape of ,a has become
 irregular1 and differs in different    
lunations4 ,at nine days after sunrise  
the craters are exactly alike in size   
and shape1 both now being elliptical1   
with their major axes lying in a nearly 
,n4 and ,s4 direction4 ,just before     

sunset ,a is again the larger1 being    
almost twice the size of ,messier4#ab   
,some observers explain this cycle of   
changes as due merely to the peculiar   
contour of the two objects1 the change  
in the lighting during the lunar day    
altering their apparent figures4 ,prof4 
,w4 ,h4 ,pickering1 on the other hand1  
while recognizing that some portion of  
the change of shape is probably due to  
the contour of the ground1 conceives    
that1 in order to explain the whole     
phenomenon1 it is necessary to suppose  
that a white layer of hoar frost is     
formed periodically round the two       
craters4 ,it is also alleged that       
whereas ,maedler described the two      
craters as being exactly alike eighty   
years ago1 ,messier ,a is now distinctly
 the larger2 but it is very doubtful    
whether ,maedler's description can be   
trusted to this degree of nicety4 ,if it
 could1 this would establish a permanent
 change in the actual structure of the  
lunar surface at this point4  ,there are

 several other cases of the same order  
of ambiguity4 ,the most celebrated is   
,linne1 a white spot about six miles in 
diameter on the ,mare ,serentatis4 ,this
 object appears to change in size during
 the progress of the lunar day1 and1 as 
with ,messier1 some selenographers      
consider that it has also suffered an   
actual permanent change in shape within 
the last sixty or seventy years4 ,here  
again the evidence is not decisive2     
,neison is by no means convinced that a 
change has taken place1 yet does not    
think it impossible that ,linne may once
 have been a crater with steep walls    
which have collapsed into its interior  
through the force of gravity4  ,another 
type of suspected change is associated  
with the neighbourhood of ,aristarchus1 
the brightest formation on the ,moon1 so
 bright indeed that ,sir ,william       
,herschel1 observing it when illuminated
 by earthshine in the dark portion of   
the ,moon1 thought that he was watching 
a lunar volcano in eruption4 ,in #ahig1 

on ,september #ba1 the late ,major      
,molesworth noticed that the crater was 
at that time under the rays of the      
setting ,sun1 and filled with shadow1   
and the inner terraces1 which should    
have been invisible1 were seen as faint1
 knotted1 glimmering streaks under both 
the eastern and western walls1 and the  
central peak was also dimly discernible4
 ,he thought this unusual lighting up of
 rocks on which the ,sun had already set
 might be due either to phosphorescence 
produced by long exposure to the ,sun's 
rays1 or to inherent heat1 or to        
reflected glare from the western        
rampart4 ,still more important1 both    
,major ,molesworth and ,mr4 ,walter     
,goodacre1 each on more than one        
occasion1 observed what seemed to be a  
faint bluish mist on the inner slope of 
the east wall1 soon after sunrise1 but  
this was visible only for a short time4 
,other selenographers too1 on rare      
occasions1 have made observations       
accordant with these1 relating to       

various regions on the ,moon4  ,these1  
and a few other similar instances1 are  
all that selenography has to offer by   
way of evidence of actual lunar change4 
,of seeming change there is abundance1  
but beyond that we have only cases for  
controversy1 and one of the most        
industrious of the present-day observers
 of the ,moon1 ,m4 ,philip ,fauth1      
declares that as a student of the ,moon 
for the last twenty years1 and as       
probably one of the few living          
investigators who have kept in practical
 touch with the results of selenography1
 he is bound to express his conviction  
that no eye has ever seen a physical    
change in the plastic features of the   
,moon's surface4#ac  ,in this matter of 
change1 then1 the ,earth and ,moon stand
 in the greatest contrast to each other4
 ,as we have seen1 from the view-point  
of the ,moon1 the appearance of the     
,earth would change so manifestly with  
the progress of the seasons that no one 
could fail to remark the difference1    

even though observing with the naked    
eye4 ,but from the view-point of the    
,earth1 the ,moon when examined by our  
most experienced observers1 armed with  
our most powerful telescopes1 offers us 
only a few doubtful enigmatical         
instances of possible change confined to
 small isolated localities2 we see no   
evidence that the gloom of iron         
substance below is ever concealed by a  
veil of changing vegetation1 or that    
between the burning light and deep      
vacuity of the heavens above1 the veil  
of the flying vapour has ever been      
spread out4 ,we see the ,moon so clearly
 that we are assured it holds no water  
to nourish plant life2 we see it so     
clearly because there is no air to carry
 the vapour that might dim our view4    
,life is change1 and a planet where     
there is no change1 or where that change
 is very small1 can be no home for life4
 ,the stability and insensibility are   
indeed required in the platform upon    
which life is to appear1 but there must 

be the presence of the passion and the  
perishing1 or life will be unable to    
find a home4  ,we infer the absence of  
water and air from the ,moon not only   
from the unchanging character of its    
features and the distinctness with which
 we see them2 we are able to make direct
 observations4 ,galileo1 the first man  
to observe the ,moon to better advantage
 than with the naked eye1 was not long  
before he decided that the ,moon        
contained no water1 for though ,milton1 
in a well-known passage1 makes ,galileo 
discover    ,rivers or mountains on her 
spotty globe1  ,galileo himself wrote3  
,i do not believe that the body of the  
,moon is composed of earth and water4   
,the name of maria was given to the     
great grey plains of the ,moon by       
,hevelius1 but this was simply for      
convenience of nomenclature1 not because
 he actually believed them to be seas4  
,one observation is1 in itself1         
sufficient to prove that the maria are  
not water surfaces4 ,the ,moon's        

terminator1 that is to say1 the line    
dividing the part in sunlight from that 
in darkness1 is clearly irregular when  
it passes over the great plains2 were   
they actually sea it would be a bright  
line and perfectly smooth4 ,the grey    
plains are therefore not expanses of    
water now1 nor were they in time past4  
,it is obvious that in some remote      
antiquity their surface was in a fluid  
condition1 but it was the fluidity of   
molten rock4 ,this is seen by the way in
 which the maria have invaded1 breached1
 broken down1 and submerged many of the 
circular formations on their margins4   
,thus the ,mare ,humorum has swept away 
half the wall of the rings1 ,hippalus   
and ,doppelmayer1 and far out in the    
open plain of the ,mare ,nubium1 great  
circles like ,kies1 and that immediately
 north of ,flamsteed1 stand up in faint 
relief as of half-submerged rings4      
,clearly there was a period after the   
age in which the great ring mountains   
and walled plains came into existence1  

when an invasive flood attacked and     
partially destroyed a large proportion  
of them4 ,and the flood itself evidently
 became more viscous and less fluid the 
further it spread from its original     
centre of action1 for the ridges and    
crumpling of the surface indicate that  
the material found more and more        
difficulty in its flow4  ,we have       
evidence just as direct that there is no
 atmosphere4 ,this is very strikingly   
shown when the ,moon1 in its monthly    
progress among the stars1 passes before 
one of them and occults it4 ,such an    
occultation is instantaneous1 and is    
particularly impressive when either a   
disappearance or a reappearance occurs  
at the defective limb2 that is to say1  
at the limb which is not illuminated by 
the ,sun1 and is therefore invisible4   
,the observer may have a bright star in 
the field of view1 showing steadily in a
 cloudless sky2 there is not a hint of a
 weakening in its light2 suddenly it is 
gone4 ,the first experience of such an  

observation is most disconcerting2 it is
 hardly less disconcerting to observe   
the reappearance at the dark limb4 ,one 
moment the field of view of the         
telescope is empty2 the next1 without   
any sort of dawning1 a bright star is   
shining steadily in the void1 and it    
almost seems to the observer as if an   
explosion had taken place4 ,if the ,moon
 had an atmosphere extending upwards    
from its surface in all directions and  
of any appreciable density1 an          
occultation would not be so exceedingly 
abrupt2 and1 in particular1 if the      
occultation were watched through a      
spectroscope1 then1 at the              
disappearance1 the spectrum of the star 
would not vanish as a whole1 but the red
 end would go first1 and the rest of the
 spectrum would be swept out of sight   
successively1 from orange to the violet4
 ,this does not happen2 the whole       
spectrum goes out together1 and it is   
clear that no appreciable atmosphere can
 exist on the ,moon4 ,in actual         

observation so inappreciable is it that 
its density at the ,moon's surface is   
variously estimated as #a_/cjjth of that
 of the ,earth by ,neison1 and as       
#a_/ajjjjth by ,w4 ,h4 ,pickering4 ,if  
the ,moon possessed an atmosphere       
bearing the same proportion to her total
 mass as we find in the case of the     
,earth1 she would have a density of     
one-fortieth of our atmosphere at the   
sea level4  ,the ,moon is at the same   
mean distance from the ,sun as the      
,earth1 and therefore1 surface for      
surface1 receives from it on the average
 the same amount of light and heat4 ,but
 it makes a very different use of these 
supplies4 ,bright as the ,moon appears  
when seen at the full on some winter    
night1 it has really but a very low     
power of reflection1 and is only bright 
by contrast with the darkness of the    
midnight sky4 ,if the full ,moon is seen
 in broad daylight1 it is pale and      
ghost-like4 ,sir ,john ,herschel has put
 it on record that when in ,south       

,africa he often had the opportunity of 
comparing the ,moon with the face of    
,table ,mountain1 the ,sun shining full 
upon both1 and the ,moon appeared no    
brighter than the weathered rock4 ,the  
best determinations of the albedo of the
 ,moon1 that is to say1 of its          
reflective power1 give it as #j4ag1 so  
that only one-sixth of the incident     
light is reflected1 the other           
five-sixths being absorbed4 ,it is      
difficult to obtain a good determination
 of the ,earth's albedo1 but the most   
probable estimate puts it as about      
#j4ej1 or three times as great as that  
of the ,moon4 ,this high reflective     
power is partly to be accounted for by  
the great extent of the terrestrial     
polar caps1 but chiefly by the clouds   
and dust layer always present in its    
atmosphere4  ,a larger proportion1      
therefore1 of the solar rays are        
employed in heating the soil of the     
,moon than in heating that of the       
,earth1 and in this connection the      

effect of an important difference       
between the two worlds must be noted4   
,the ,earth rotates on its axis in #bc  
hours #ef minutes #d seconds1 the mean  
length of its rotation as referred to   
the ,sun being #bd hours4 ,the rotation 
of the ,moon1 on the other hand1 takes  
#bg days #g hours #dc minutes to        
accomplish1 giving a mean rotation1 as  
referred to the ,sun1 of #bi days #ab   
hours #dd minutes4 ,the lunar surface is
 therefore exposed uninterruptedly to   
the solar scorching for very nearly     
fifteen of our days at a time1 and it   
is1 in turn1 exposed to the intense cold
 of outer space for an equal period4 ,as
 the surface absorbs heat so readily1 it
 must radiate it as quickly2 hence      
radiation must go on with great rapidity
 during the long lunar night4 ,lord     
,rosse and ,prof4 ,very have both       
obtained measures of the change in the  
lunar heat radiation during the progress
 of a total eclipse of the ,moon1 with  
the result that the heat disappeared    

almost completely1 though not quite at  
the same time as the light4 ,prof4      
,langley succeeded in obtaining from the
 ,moon1 far down in the long wave       
lengths of the infra-red1 a heat        
spectrum which was only partly due to   
reflection from the ,sun2 part coming   
from the lunar soil itself1 which1      
having absorbed heat from the ,sun1     
radiated it out again almost            
immediately4 ,in #ahih1 ,prof4 ,very1   
following up ,langley's line of work1   
concluded that the temperature of the   
lunar soil must range through about #cej
 deg4 ,centigrade1 considerably         
exceeding #ajj deg4 at the height of the
 lunar day1 and falling to about the    
temperature of liquid air during the    
lunar night4 ,so wide a range of        
temperature must be fatal to living     
organisms1 particularly when the range  
is repeated at short1 regular intervals 
of time4 ,but this range of temperature 
comes directly from the length of the   
,moon's rotation period2 for the longer 

the day of the ,moon1 the higher the    
temperature which may be attained in it2
 the longer the night1 the greater the  
cold which will in turn be experienced4 
,we learn1 therefore1 that the time of  
rotation of a planet is an important    
factor in its habitability4             
,,chapter ,,vi  ,,the ,,canals ,,of     
,,mars   ,both of the two worlds best   
placed for our study are thus1 for      
different reasons1 ruled out of court as
 worlds for habitation4 ,the ,sun by its
 vastness1 its intolerable heat and the 
violence of its changes1 has to be      
rejected on the one hand1 while the     
,moon1 so small1 and therefore so rigid1
 unchanging and bare1 is rejected on the
 other4  ,of the other heavenly bodies1 
the planet ,mars is the one that we see 
to best advantage4 ,two other planets1  
,eros and ,venus1 at times come nearer  
to us1 but neither offers us on such    
occasions equal facilities for their    
examination4 ,but of ,mars it has been  
asserted not only that it is inhabited1 

but that we know it to be the case1     
since the evidence of the handiwork of  
intelligent beings is manifest to us1   
even across the tremendous gulf of forty
 or more million miles of space4  ,a    
claim so remarkable almost captures the 
position by its audacity4 ,there is a   
natural desire among men to believe the 
marvellous1 and the very boldness of the
 assertion goes no small way to overcome
 incredulity4 ,and when we consider how 
puny are men as we see them on this our 
planet1 how minute their greatest works1
 how superhuman any undertaking would be
 which could demonstrate our existence  
to observers on another planet1 we must 
admit that it is a marvel that there    
should be any evidence forthcoming that 
could bear one way or another on the    
solution of a problem so difficult4     
,the first fact that we have to remember
 with regard to the planet ,mars is the 
smallness of its apparent size4 ,to the 
eye it is nearly a star--a point of     
light without visible surface4 ,it is   

almost twice the size of the ,moon in   
actual diameter1 but as its mean        
distance from the ,earth is #fjj times  
that of the ,moon1 its mean apparent    
diameter is #cjj times smaller4 ,we     
cannot1 however1 watch ,mars in all     
parts of its orbit2 it is best placed   
for observation1 and1 therefore1 most   
observed1 when in opposition1 and       
oppositions may be favourable or        
unfavourable4 ,at the most favourable   
opposition1 ,mars is #adj times as      
distant as the ,moon2 at the least      
favourable1 #bfj times2 so that on such 
occasions its apparent size varies from 
#a_/gjth of the diameter of the ,moon to
 #a_/acjth4 ,but a telescope with a     
magnifying power of #gj could never1    
under the most perfect conditions1 show 
,mars1 even in the closest opposition1  
as well as the ,moon is seen with the   
naked eye1 for the practical magnifying 
power of a telescope is never as great  
as the theoretical4 ,in practice1 a     
child's spy-glass magnifying some six   

diameters will show the full ,moon to   
better advantage than ,mars has ever    
been seen1 even in our most powerful    
telescopes4  ,the small apparent size of
 the planet explains how it was that    
,galileo does not seem to have been able
 to detect any markings upon it4 ,in    
#afei1 ,huyghens laid the foundation    
stone of areography by observing some   
dark spots1 and determining from their  
apparent movements that the planet had a
 rotation on its axis1 which it         
accomplished in about the same time as  
the ,earth4 ,small and rough as are the 
drawings that ,huyghens made1 the       
identification of one or two of his     
spots is unmistakable4 ,seven years     
later1 in #afff1 both ,cassini and      
,hooke made a number of sketches1 and   
those by ,hooke have been repeatedly    
used in modern determinations of the    
rotation period of the planet4 ,the next
 great advance was made by ,sir ,william
 ,herschel1 who1 during the oppositions 
of #aggg1 #aggi1 #agha1 and #aghc1      

determined the inclination of the axis  
of ,mars to the plane of its orbit1     
measured its polar and equatorial       
diameters1 and ascertained the amount of
 the polar flattening4 ,he paid also    
special attention to two bright white   
spots upon the planet1 and he showed    
that these formed round the planet's    
poles and increased in size as the      
winter of each several hemisphere drew  
on and diminished again with the advance
 of summer1 behaving therefore as do the
 snow caps of our own polar regions4    
,the next stage in the development of   
our knowledge of ,mars must be ascribed 
to the two ,german astronomers1 ,beer   
and ,maedler1 who made a series of      
drawings in the years #ahcj1 #ahcb and  
#ahcg1 by means of a telescope of #d    
inches aperture1 from which they were   
able to construct a chart of the entire 
globe4 ,this chart may be considered    
classic1 for the features which it      
represents have been observed afresh at 
each succeeding opposition4 ,mars1      

therefore1 possesses a permanent        
topography1 and some of the markings in 
question can be identified1 not only in 
the rough sketches made by ,sir ,william
 ,herschel1 but even in those made by   
,hooke and ,cassini as far back as the  
year #afff4 ,in the forty years that    
followed1 the planet was studied by many
 of the most skilled observers1         
particularly by ,mr4 ,j4 ,n4 ,lockyer in
 #ahfb1 and the ,rev4 ,w4 ,r4 ,dawes in 
#ahfd4 ,in #ahgg1 the late ,mr4 ,n4 ,e4 
,green1 drawing-master to ,queen        
,victoria1 and a distinguished painter  
in water colours1 made a series of      
sketches of the planet from a station in
 the island of ,madeira #bjjj feet above
 sea-level4 ,when the opposition was    
over1 ,mr4 ,green collected together a  
large number of drawings1 and formed a  
chart of the planet1 much richer in     
detail than any that had preceded it1   
and from his skill1 experience and      
training as an artist he reproduced the 
appearance of the planet with a fidelity

 that had never been equalled before and
 has never been surpassed since4 ,at    
this time it was generally assumed that 
,mars was a miniature of our own world4 
,the brighter districts of its surface  
were supposed to be continents1 the     
darker1 seas4 ,as ,sir ,william         
,herschel had already pointed out long  
before1 the little world evidently had  
its seasons1 its axis being inclined to 
the plane of its orbit at much the same 
angle as is the case with the ,earth2 it
 had its polar caps1 presumably of ice  
and snow2 its day was but very little   
longer than that of the ,earth2 and the 
only important difference seemed to be  
that it had a longer year1 and was a    
little further off the ,sun4 ,but the   
general conclusion was that it was so   
like the ,earth in its conditions that  
we had practically found out all that   
there was to know2 all that seemed to be
 reserved for future research was that a
 few minor details of the surface might 
be filled in as the power of our        

telescopes was increased4  ,but         
fortunately for progress1 this sense of 
satisfaction was to be rudely disturbed4
 ,as ,mars1 in its progress round the   
,sun1 receded from the ,earth1 or rather
 as the ,earth moved away from it1 the  
astronomers who observed so diligently  
during the autumn of #ahgg turned their 
attention to other objects4 ,one of     
them1 however1 ,schiaparelli1 the most  
distinguished astronomer on the         
continent of ,europe1 still continued to
 watch the planet1 and1 as the result of
 his labours1 he published some months  
later the first of a magnificent series 
of ,memoirs1 bringing to light what     
appeared to be a new feature4 ,his      
drawings not only showed the lands and  
seas1 that is to say the bright and dark
 areas1 that ,green and his predecessors
 had drawn1 but also a number of fine1  
narrow1 dark lines crossing the lands in
 every direction4 ,these narrow lines   
are the markings which have since been  
so celebrated as the canals of ,mars1   

and the discussion as to the real nature
 of these canals has focussed attention 
upon ,mars in a way that1 perhaps1      
nothing else could have done4 ,before   
#ahgg the study of planetary markings   
was left almost entirely to the         
desultory labours of amateurs1 skilled  
though many of them were2 since #ahgg1  
the most powerful telescopes of the     
great public observatories of the world 
have been turned upon ,mars1 and the    
most skilful and experienced of         
professional astronomers have not been  
ashamed to devote their time to it4     
,there is no need to pass in review the 
whole of the immense mass of            
observations that have been accumulated 
since ,schiaparelli brought out the     
first of his great ,memoirs4 ,that      
,memoir gave rise to an immediate       
controversy1 for many astronomers of    
skill and experience had observed the   
planet in #ahgg without detecting the   
network of lines which ,schiaparelli had
 revealed1 and it was natural that they 

should feel some reluctance in accepting
 results so strange and novel4 ,but     
little by little this controversy has   
passed4 ,we now know that the canals    
vary much in their visibility1 and      
curiously enough the canals are most    
conspicuous1 not at the time the planet 
is nearest to the ,earth and its general
 features are in consequence best seen1 
but as the planet goes away the canals  
come out4 ,the fact is that the orbital 
position and the seasonal epoch conspire
 to a masking of the phenomena4 ,this   
was the chief reason why ,schiaparelli's
 discoveries seemed at first to stand so
 entirely without corroboration2 the    
canals did not become conspicuous until 
after most observers had desisted from  
following the planet4 ,another reason   
was that1 in #ahgg1 ,mars was low down  
in the sky for northern observatories1  
and good definition is an essential for 
their recognition4 ,but the careful     
examination of drawings made in earlier 
oppositions1 especially those made by   

,dawes and ,green1 afforded confirmation
 of not a few of ,schiaparelli's canals2
 even in #ahgg a few of the easiest and 
most conspicuous had been delineated by 
other astronomers before any rumour of  
,schiaparelli's work had come abroad1   
and as ,mars came under observation     
again and again at successive           
oppositions1 the number of those who    
were able to verify ,schiaparelli's     
discoveries increased4 ,it has now long 
been known that the great ,italian      
astronomer was not the victim of a mere 
optical illusion2 there were actual     
markings on the planet ,mars where he   
had represented them2 markings which1   
when seen under like conditions and with
 equal instrumental equipment1 did      
present the appearance of straight1     
narrow lines4 ,the canals of ,mars are  
not mere figments of the imagination1   
but have a real objective basis4  ,as   
this controversy has passed away1       
another and a very different one has    
arisen out of an unfortunate            

mistranslation of the term chosen by    
,schiaparelli to indicate these linear  
streaks4 ,in conformity with the type of
 nomenclature adopted by previous       
areographers who had divided ,mars into 
seas1 continents1 islands1 isthmuses1   
straits and the like1 ,schiaparelli had 
called the narrow lines he detected     
canali1 that is to say channels1 but    
without intending to convey the idea of 
artificial construction4 ,indeed1 he    
himself was careful to point out that   
these designations were not intended to 
prejudge the nature of the spot1 and    
were nothing but an artifice for helping
 the memory and for shortening          
descriptions4 ,and he added1 ,we speak  
in the same way of the lunar seas1      
although we well know that there are no 
true seas on the ,moon4 ,but canali was 
unhappily rendered in ,english as       
canals1 instead of channels4 ,channel   
would have left the nature of the       
marking an open question1 but1 in       
,english1 canal means an artificial     

waterway4 ,here then the question as to 
whether or no ,mars is inhabited comes  
definitely before us4 ,have we          
sufficient grounds for believing that   
the canals are artificial constructions1
 or may they be merely natural          
formations8  ,in #ahid1 ,mr4 ,percival  
,lowell founded at ,flagstaff1 ,arizona1
 ,u4,s4,a41 a well-equipped observatory 
for the special study of ,mars1 and he  
has continued his scrutiny of the planet
 from that time to the present with the 
most unrelaxing perseverance4 ,the chief
 results that he has obtained have been 
the detection of many new canals2 the   
discovery of a number of dark1 round    
dots1 termed by him oases1 at the       
junctions of the canals2 and the        
demonstration that the canals and       
certain of the dusky regions are subject
 to strictly seasonal change1 as really 
as the polar caps themselves4 ,in       
addition1 he has formed the conclusion1 
which he has supported with much        
ingenuity and skill1 that the regularity

 of the canals and oases quite precludes
 the possibility of their being natural 
formations4 ,hence there has arisen the 
second controversy3 that on the nature  
of the canals2 for ,mr4 ,lowell         
considers that their presence proves the
 existence of inhabitants on ,mars1 who1
 by means of a ,titanic system of       
irrigation1 are fighting a losing battle
 against the gradual desiccation of     
their planet4  ,in a paper published in 
the ,international ,scientific ,review1 
,scientia1 in ,january1 #aiaj1 ,mr4     
,lowell gave a summary of his argument4 
,organic life needs water for its       
existence4 ,this water we see exists    
on ,mars1 but in very scant amount1 so  
that if life of any sort exists         
there1 it must be chiefly dependent on  
the semi-annual unlocking of     the    
polar snows for its supply1 inasmuch as 
there are no surface     bodies of it   
over the rest of the planet4 ,now the   
last few years1     beginning with      
,schiaparelli in #ahgg1 and much        

extended since at     ,flagstaff1 have  
shown3      ,the surface of the planet  
to be very curiously meshed by a fine   
network of lines and spots4      ,now if
 one considers first the appearance of  
this network of lines     and spots1 and
 then its regular behaviour1 he will    
note that its     geometrism precludes  
its causation on such a scale by any    
natural     process and1 on the other   
hand1 that such is precisely the aspect 
which an artificial irrigating system1  
dependent upon the melting of     the   
polar snows1 would assume4 ,since water 
is only to be had at the     time it is 
there unlocked1 and since for any       
organic life it must be     got1 it     
would be by tapping the disintegrated   
cap1 and only so1 that     it could be  
obtained4 ,if ,mars be inhabited1       
therefore1 it is precisely     such a   
curious system we should expect to see1 
and only by such     explanation does it
 seem possible to account for the facts4
      ,these lines are the so-called    

canals of ,mars4 ,it is not supposed    
that     what we see is the conduit     
itself4 ,on the contrary1 the behaviour 
of     these lines indicates that what  
we are looking at is vegetation4 ,now1  
vegetation can only be induced by a     
water-supply4 ,what we see     resembles
 the yearly inundation of the ,nile1 of 
which to a spectator     in space the   
river itself might be too narrow to be  
seen1 and only the     verdured country 
on its banks be visible4 ,this is what  
we suppose to     be the case with      
,mars4 ,however the water be conducted1 
whether in     covered conduits1 which  
seems probable1 or not1 science is not  
able to     state1 but the effects of it
 are so palpable and so exactly in      
accord     with what such a system of   
irrigation would show1 that we are      
compelled to believe that such is indeed
 its vera causa4  ,beside the bulky     
,memoirs in which ,prof4 ,lowell has    
published the scientific results        
obtained at his observatory at          

,flagstaff1 and papers and articles     
appearing in various scientific         
journals1 he has brought out three books
 of a more popular character3 ,mars2    
,mars and its ,canals2 and ,mars as the 
,abode of ,life4 ,in these he shows that
 to the assiduity of the astronomer he  
adds the missionary's zeal and eagerness
 for converts as he pleads most         
skilfully for the acceptance of his     
chosen doctrine of the presence of men  
on ,mars4 ,in the last of the three     
books mentioned1 he deals directly with 
,proofs of ,life on ,mars4 ,the presence
 of vegetation may be inferred from     
seasonal changes of tint1 just as an    
observer on the ,moon might with the    
naked eye watch effects on the ,earth4  
,but though vegetable life could thus   
reveal itself directly1 animal life     
could not4 ,not by its body but by its  
mind would it be known4 ,across the gulf
 of space it could be recognized only by
 the imprint it had made on the face of 
,mars4      ,confronting the observer   

are lines and spots that but impress him
 the     more1 as his study goes on1    
with their non-natural look4 ,so        
uncommonly     regular are they1 and on 
such a scale as to raise suspicions     
whether     they can be by nature       
regularly produced 7p4 #ahh74      444  
,unnatural regularity1 the observations 
showed1 betrays itself in     everything
 to do with the lines3 in their         
surprising straightness1     their      
amazing uniformity throughout1 their    
exceeding tenuity1 and     their immense
 length 7p4 #ahi74      ,as a planet    
ages1 its surface water grows scarce4   
,its oceans in time     dry up1 its     
rivers cease to flow1 its lakes         
evaporate 7p4 #bjc74444     ,now1 in the
 struggle for existence1 water must be  
got4444 ,its     procuring depends on   
the intelligence of the organisms that  
stand in     need of it4444 ,as a planet
 ages1 any organisms upon it will share 
in     its development4 ,they must      
evolve with it1 indeed1 or perish4 ,at  

first     they change only1 as          
environment offers opportunity1 in a    
lowly1     unconscious way4 ,but1 as    
brain develops1 they rise superior to   
such     occasioning4444 ,the last stage
 in the expression of life upon a       
planet's surface must be that just      
antecedent to its dying of              
thirst4444 ,with an intelligent         
population this inevitable end would be 
long foreseen4444 ,both polar caps would
 be pressed into service in     order to
 utilize the whole available supply and 
also to accommodate     most easily the 
inhabitants of each hemisphere 7pp4     
#bjd-aa74      ,that intelligence should
 thus mutely communicate its existence  
to us     across the far reaches of     
space1 itself remaining hid1 appeals to 
all     that is highest and most        
far-reaching in man himself4 ,more      
satisfactory than strange this2 for in  
no other way could the     habitation of
 the planet have been revealed4 ,it     
simply shows again the     supremacy of 

mind4444 ,thus1 not only do the         
observations we have     scanned lead us
 to the conclusion that ,mars at this   
moment is     inhabited1 but they land  
us at the further one that these        
denizens are     of an order whose      
acquaintance was worth the making 7p4   
#bae74  ,for the moment1 let us leave   
,prof4 ,lowell's argument as he puts it4
 ,whether we accept it or not1 it       
remains that it is a marvellous         
achievement of the optician's skill and 
the observer's devotion that from a     
planet so small and so distant as ,mars 
any evidence should be forthcoming at   
all that could bear upon the question of
 the existence of intelligent organisms 
upon its surface4 ,but it is of the     
utmost significance to note that the    
whole question turns upon the presence  
of water--of water in the liquid state1 
of water in a sufficient quantity2 and  
the final decision1 for ,mr4 ,lowell's  
contention1 or against it1 must turn on 
that one point4 ,the search for ,life on

 ,mars is essentially a search for      
,water2 a search for water1 not only in 
the present state of ,mars1 but in its  
past as well4 ,for1 without water in    
sufficient quantities in the past1 life 
on ,mars could not have passed through  
the evolutionary development necessary  
to its attaining its highest            
expression1--that where the material    
living organism has become the          
tabernacle and instrument of the        
conscious intelligent spirit4           
,,chapter ,,vii  ,,the ,,condition ,,of 
,,mars   ,the planet ,mars is the       
debatable ground between two opinions4  
,here1 the two opposing views join      
issue2 the controversy comes to a focus4
 ,the point in debate is whether certain
 markings--some linear1 some            
circular--are natural or artificial4    
,if1 it is argued1 some are truly like a
 line1 without curve or break1 as if    
drawn with pen1 ink1 and ruler2 or      
others1 so truly circular1 without      
deviation or break1 as if drawn with    

pen1 ink1 and compass2 if1 moreover1    
when we obtain more powerful telescopes1
 erected in better climates for         
observing1 these markings become more   
truly lines and circles the better we   
see them2 then they are artificial1 not 
natural structures4  ,but artificial    
structures imply artificers4 ,and if the
 structures are so designed as to meet  
the needs of a living organism1 it      
implies that the living organism that   
designed them must have a reasonable    
mind lodged in a natural body4 ,if1     
then1 the lines and circles that ,prof4 
,lowell and his disciples assert to be  
artificial canals and oases are really  
such1 they premise the order of being   
that we call ,man4 ,but these canals and
 oases also premise the liquid that we  
call ,water--water that flows and water 
utilized in cultivation4 ,in this       
chapter we will leave out of count the  
first premiss--,man--and only deal with 
what concerns the second                
premiss--,water2 with water that flows  

and is utilized in vegetation4          
,,planetary ,,statistics                
----------------------------------------
----------------------------            
,minor            ,inner                
,planets4                               
----------------------------------------
--------------------------              
,ceres   ,moon  ,mercury                
----------------------------------------
--------------------------              
,,proportions ,,of ,,the ,,planets3--   
,diameter in miles                      
#dgg   #bafc   #cjcj                    
,symbol  #a                        #j4jf
   #j4bgc  #j4chc     ,surface1 ,symbol 
#a                        #j4jjd  #j4jge
  #j4adg     ,volume1  ,symbol  #a      
#j4jjjb #j4jb   #j4jf      ,density1    
,water  #a                              
#b4h 8  #c4ci   #d4gb                   
,symbol  #a                        #j4e 
8  #j4fa   #j4he      ,mass1    ,symbol 
#a                        #j4jjja #j4jab
  #j4jdh     ,gravity at surface1       

,symbol  #a             #j4jbh  #j4ag   
#j4cc      ,rate of ,fall1 ,feet in the 
,first ,second       #j4de   #b4gc      
#e4cj      ,albedo                      
#j4ad   #j4ag   #j4ad                   
,,details ,,of ,,orbit3--               
,mean ,distance from ,sun in millions of
 miles#beg4a   #ib4i   #cf4j            
,earth's distance  #a     #b4gfg  #a4jjj
  #j4chg     ,period of ,revolution1 in 
years               #d4fj   #a4jj       
#j4bd      ,velocity1 in miles per      
second               #aa4a   #ah4e      
#i4g       ,eccentricity                
#j4jgfc #j4jafh #j4bjef    ,aphelion    
,distance1 ,perihelion  #a              
#a4aeg  #a4jcd  #a4eag     ,inclination 
of ,equator to ,orbit              787  
#a deg44#cb'  787                       
d h m    d       ,rotation period       
787   #bg4g4dc #hh787                   
,,atmosphere1 assuming the total mass of
 the                                    
atmosphere to be proportional to the    
mass                            of the  

planet3--                               
,pressure at the surface in lb4 per sq4 
in4   #j4jad  #j4dj   #a4f              
in atmospheres     #j4jjji #j4jbg       
#j4ajh     ,level of half surface       
pressure in miles    #aai4j   #ai4f     
#aj4a       ,boiling point of water at  
the surface               #bb deg4,c    
#ec deg4,c                              
,,temperature3--                        
,light and heat received from ,sun1     
,symbol  #a   #j4ac   #a4jj   #f4fg     
,reciprocal of square-root of distance1 
,symbol  #a   #j4fj   #a4jj   #a4fa     
,equatorial temp4 of ideal planet1      
,absolute    #ahh    #cab deg4   #ejb   
deg4                                    
,centigrade   -#fe    #ci   #bbi        
,average temp4 of ideal planet1         
,absolute       #agd    #bij    #dfg    
,centigrade     -#ii    #ag   #aid      
,upper limit under zenith sun1 ,absolute
        #bdh    #dab    #ffd            
,centigrade      -#be   #aci   #cia     
,average temp4 of equivalent disc1      

,absolute    #bbc    #cga    #eih       
,centigrade   -#ej    #ih   #cbe        
----------------------------------------
--------------------------              
----------------------------------------
------------------------    ,planets4   
,outer ,planets4                        
----------------------------------------
-------------------     ,mars   ,venus  
,earth   ,uranus   ,neptune  ,saturn    
,jupiter                                
----------------------------------------
-------------------                     
#dbcj    #ggjj    #giah     #caijj      
#cdhjj   #gcjjj    #hfejj      #j4ecd   
#j4igb   #a4jjj    #d4jbi    #d4cie     
#i4bai   #aj4ibd      #j4bhe   #j4ide   
#a4jjj   #af4b     #ai4c    #he4j       
#aai4c        #j4ae    #j4ib    #a4jj   
#fe4      #he4    #gfj4    #acjd4       
#c4ib    #d4id    #e4ee     #a4bb       
#a4aa    #j4gb     #a4cb       #j4ga    
#j4hi    #a4jj     #j4bb     #j4bj      
#j4ac     #j4bd       #j4ajg   #j4hbj   
#a4jjj   #ad4f     #ag4j    #id4h       

#cag4g        #j4ch    #j4hg    #a4jj   
#j4ij     #j4hi    #a4ah     #b4fe      
#f4aa   #ac4ii   #af4jh    #ad4dg       
#ad4ca   #ah4ig    #db4fa       #j4bb   
#j4gf    #j4ej8    #j4fj     #j4eb      
#j4gb     #j4fb                         
#ada4e    #fg4b    #ib4i   #agha4i      
#bgia4f   #hhf4j    #dhc4c        #a4ebd
   #j4gbc   #a4jjj   #ai4ahc   #cj4jee  
#i4eci    #e4bjc      #a4hh    #j4fb    
#a4jj    #hd4jb   #afd4gh   #bi4df      
#aa4hf      #ae4j    #ba4i    #ah4e     
#d4b      #c4d     #f4j      #h4a       
#j4jicc  #j4jjfh  #j4jafh   #j4jdfc     
#j4jjij  #j4jefa   #j4jdhc     #a4bjg   
#a4jac   #a4jcd    #a4jig    #a4jah     
#a4ajg    #a4aja    #bd deg44#j'    787 
#bc deg44#bg'   787      787    #bf     
deg44#di'  #c deg44#e'     h  m  s      
h  m  s h m               h  m    h  m  
#bd4cg4bc  787    #bc4ef4d #i4cj787     
787     #aj4ad-  #i4ee-                 
#b4a    #aa4a    #ad4g     #aa4i        
#aa4e    #ai4d    #ajc4h        #j4adc  
#j4ged   #a4jjj    #j4ha     #j4gh      

#a4cb     #g4jf       #h4h     #c4h     
#c4c      #c4g      #c4h     #b4h       
#a4c        #ec deg4,c    #ib deg4,c    
#ajj deg4,c    #id deg4,c     #ic deg4,c
    #ajh deg4,c    #aff deg4,c          
#j4dc    #a4ia    #a4jj     #j4jjc      
#j4jja   #j4jaa    #j4jcg      #j4ha    
#a4ah    #a4jj     #j4bc     #j4ah      
#j4cb     #j4dd        #bec deg4    #cfh
 deg4    #cab deg4     #ga deg4      #ef
 deg4     #aja deg4     #acg deg4       
-#bj     #ie     #ci     -#bjb     -#bag
    -#agb     -#acf        #bce     #cdb
     #bij      #ff       #eb      #id   
#abg        -#ch     #fi     #ag        
-#bjg     -#bba    -#agi     -#adf      
#ccg     #dhf     #dab      #id         
#gd      #acc      #ahj        #fd      
#bac    #aci     -#agi     -#aii        
-#adj      -#ic        #cjj     #dch    
#cga      #hd       #fg      #abj       
#afb        #bg    #afe     #ih         
-#ahi     -#bjf    -#aec     -#aaa      
----------------------------------------
-------------------  ,for in regard to  

this particular premiss we can do away  
with hypothesis1 and deal only with     
certain physical facts that are not     
controversial and are not in dispute4   
,the first of this series of facts      
concerning ,mars about which there can  
be no controversy or dispute relates to 
its size and mass4 ,as the foregoing    
,table shows1 it comes between the ,moon
 and the ,earth in these respects4  ,the
 figures show at a glance that ,mars    
ranks in its dimensions between the     
,moon and the ,earth1 and that1 on the  
whole1 it is more like to the ,moon than
 it is to the ,earth4  ,but in what way 
would this affect ,mars as a suitable   
home for life8 ,in many ways2 and       
amongst these the distribution of its   
atmosphere and the sluggishness of its  
atmospheric circulation are not the     
least important4  ,it was mentioned in  
,chapter ,,iii that at a height of about
 three and a third miles the barometer  
will stand at #ae inches1 or half its   
mean height at sea level1 showing that  

one half the atmosphere has been passed 
through4 ,mont ,blanc1 the highest      
mountain in ,europe1 is under #c miles  
in height1 so that it is not possible1  
in ,europe1 to climb to the level of    
half-pressure2 ,mt4 ,everest1 the       
highest mountain in the world1 is not   
quite six miles high1 so that no part of
 the solid substance of our planet      
reaches up to the level of the quarter  
pressure4 ,on a very few occasions      
daring aeronauts have soared into the   
empyrean higher than the summits of even
 our loftiest mountains1 but the        
excursion has been a dangerous one1 and 
they have with difficulty brought their 
life back from so rare and cold1 so     
inhospitable a region4 ,when            
,gay-,lussac1 in #ahjd1 attained a      
height of #bc1jjj feet above sea level1 
the thermometer1 which on the ground    
read #ca deg4 ,c41 sank to #i deg4 below
 zero1 and the rare atmosphere was so   
dry that paper crumpled up as if it had 
been placed near the fire1 and his pulse

 rose to #abj pulsations a minute       
instead of his normal #ff4 ,when ,mr4   
,glaisher and ,mr4 ,coxwell made their  
celebrated ascent between #a and #b     
o'clock on the afternoon of ,september  
#e1 #ahfa1 they found that at a height  
of #ba1jjj feet the temperature sank to 
-#aj4d deg42 at #bf1jjj feet to -#ae4b  
deg42 and at #ci1jjj feet the           
temperature was down to -#af4j deg4 ,c4 
,at this height the rarefaction of the  
air was so great and the cold so intense
 that ,mr4 ,glaisher fainted1 and ,mr4  
,coxwell's hands being rendered numb and
 useless by the cold1 he was only able  
to bring about their descent in time by 
pulling the string of the safety valve  
with his teeth4 ,yet when they attained 
this height they were far above all     
cloud or mist1 and the ,sun's rays fell 
full upon them4 ,the ,sun's rays had all
 the force that they had at the surface 
of the ,earth1 but in the rare          
atmosphere of seven miles above the     
,earth1 the radiation from every        

particle not in direct sunlight was so  
great that while the right hand1 exposed
 to the ,sun1 might burn1 the left hand1
 protected from his direct rays1 might  
freeze4  ,but gravity at the surface of 
,mars is much feebler than at the       
surface of the ,earth1 and in order to  
reach the level of half-pressure a      
,martian mountaineer would have to      
climb1 not three and a third miles1 but 
eight and three-quarter miles2 that is  
to say1 the distance to be ascended is  
in the inverse proportion of the force  
of gravity at the surface of the planet4
 ,the atmosphere of ,mars1 therefore1 is
 much deeper than that of the ,earth1   
and one great cause of precipitation    
here is much weakened there4 ,a current 
of air heavily laden with moisture1 if  
it encounters a range of mountains1 is  
forced upwards1 and consequently        
expands1 owing to the diminished        
pressure4 ,the expansion brings about a 
cooling1 and from both causes the       
atmosphere is unable to retain as much  

water-vapour as it carried before4 ,on  
,mars1 the same relative expansion and  
cooling would only follow if the ascent 
were nearly three times as great1 and   
the feeble force of gravity has its     
effect in another way2 for just as a    
weight on ,mars will only fall six feet 
in the first second as against sixteen  
on the ,earth1 so a dense and heavy     
column of air will fall with            
proportionate slowness and a light      
column ascend in the same languid       
manner4 ,an ascending current on ,mars  
would therefore take #a_/j4ch x #a_/j4ch
  #a_/j4ade1 or seven times as long to  
attain the same relative expansion as on
 the ,earth4  ,the winds of ,mars are   
therefore sluggish1 and precipitation is
 slight4 ,so far at least it resembles  
,the island valley of ,avilion2   ,where
 falls not hail1 or rain1 or any snow1  
,nor ever wind blows loudly2  and ,r4   
,a4 ,proctor1 acute and accurate writer 
on planetary physics as he was1 fell    
into a mistake when he referred to ,mars

 as being hurricane-swept4 ,there are no
 hurricanes on ,mars2 its fiercest winds
 can never exceed in violence what a    
sailor would call a capful4  ,this holds
 good for ,mars1 but it also holds good 
for every planet where the force of     
gravity at the surface is relatively    
feeble4 ,the greater the force of       
gravity the more active the atmospheric 
circulation1 and more violent its       
disturbances2 the feebler the action of 
gravity the more languid the            
circulation1 and the slighter the       
disturbances4  ,the atmosphere of ,mars 
is relatively deeper than that of the   
,earth1 so that we1 in observing the    
details of its surface1 are looking down
 through an immense thickness of an     
obscuring medium4 ,and yet the details  
of the surface are seen with remarkable 
distinctness2 not as clearly indeed as  
we can see those of the ,moon1 but      
nearly so4 ,for instance1 the canals    
appear to have a breadth of from #ae to 
#bj miles1 corresponding to #a_/afth1   

and #a_/abth1 of a second of arc1 at an 
average opposition4 ,the oases1 as a    
rule1 are about #abj miles in diameter1 
that is to say about half a second of   
arc4 ,these are extraordinarily fine    
details to be perceived and held1 even  
if ,mars had no atmosphere at all2 it   
would certainly be impossible to detect 
them unless the atmosphere were         
exceedingly thin and transparent4 ,for  
we must remember that1 though our own   
atmosphere is a hindrance to our        
observing1 yet the atmosphere of the    
planet into which we are looking is a   
greater hindrance still4 ,like the lace 
curtains of the window of a house1 it is
 a much greater obstacle to looking     
inward than to looking outward1 and as  
the perfect distinctness with which we  
see the ,moon is a proof that it is     
practically without an atmosphere1 so   
the great detail visible on ,mars bears 
unmistakable testimony to the slightness
 of the atmospheric veil around that    
planet4  ,and when we turn again to the 

statistics of ,mars1 we see that this   
must inevitably be the case4 ,of two    
planets1 one heavier than the other1 it 
is not possible to suppose that the     
lighter should secure the greater       
proportional amount of atmosphere4 ,with
 planets1 as with persons1 it is the    
most powerful that gets the lion's      
share3 to him that hath it is given1 and
 from him that hath not is taken away   
even that which he seemeth to have4 ,but
 if we assume that ,mars has acquired an
 atmosphere proportional to its mass1   
then we see from the ,table that this   
must be a little less than #a_/ith of   
that of the ,earth2 exactly #j4ajg4 ,it 
is distributed over a smaller surface1  
#j4bhe4 ,consequently the amount of air 
above each square inch of ,martian      
surface is #j4ajg _/ #j4bhe  #j4ch4 ,but
 since the force of gravity at the      
surface of ,mars is less than on the    
,earth1 this column of air will only    
weigh #j4ch x #j4ch  #j4ade2 or         
one-seventh of the column of air resting

 on a square inch of the ,earth's       
surface4 ,the pressure at the surface of
 ,mars will therefore be #b4a lb42 and  
the aneroid barometer would read #d4c   
inches4 7,in order to express the       
diminished pressure of the ,martian     
atmosphere1 it is necessary to refer it 
to the aneroid barometer4 ,the mercury  
in a mercurial barometer1 or the water  
in a water barometer would lose in      
weight in consequence of the diminished 
force of gravity in the same proportion 
as the air would1 and the mercurial     
barometer would read #aa4d inches47     
,but a pressure of #b4a lb4 on the      
square inch is far less than that       
experienced by ,coxwell and ,glaisher in
 their great ascent2 it is about        
one-half the pressure that is           
experienced on the top of the very      
highest terrestrial mountains4 ,but the 
habitable regions of the ,earth do not  
extend even so far upward as to the     
level of a pressure of #g4c lb4 on the  
square inch2 that is1 of half the       

terrestrial surface pressure4 ,plant    
life dies out before we reach that      
point1 and though birds or men may      
occasionally attain greater heights1    
they cannot domicile there1 and are1    
indeed1 only able thus to ascend in     
virtue of nourishment which they have   
procured in more favoured regions4 ,if  
we could suppose the conditions of the  
whole ,earth changed to correspond with 
those prevailing at the summit of ,mt4  
,everest1 or even at the summit of ,mont
 ,blanc1 it is clear that the life now  
present on this planet would be         
extinguished1 and that speedily4 ,much  
more would this be the case if the      
atmosphere were diminished to one half  
the pressure on the summit of the       
highest earthly mountain4  ,the tenuity 
of the atmosphere on ,mars has another  
consequence4 ,here water freezes at #j  
deg4 ,c4 and boils at #ajj deg4 ,c42 so 
that for one hundred degrees it remains 
in a liquid condition4 ,on ,mars1 under 
the assumed conditions1 water would boil

 at #ec deg4 ,c41 and the range of      
temperature within which it would be    
liquid would be much curtailed4 ,but it 
is only water in the liquid state that  
is useful for sustaining life4  ,the    
above estimate of the density of the    
atmosphere of ,mars is an outside limit1
 for it assumes that ,mars has retained 
an atmosphere to the full proportion of 
its mass4 ,but as the molecules of a gas
 are in continual motion1 and in every  
direction1 the lighter1 most swiftly    
moving molecules must occasionally be   
moving directly outwards from the planet
 at the top of their speed1 and in this 
case1 if the speed of recession should  
exceed that which the gravity of the    
planet can control1 the particle is lost
 to the planet for ever4 ,a small planet
 therefore is subject to a continual    
drain upon its atmosphere1 a drain of   
the lightest constituents4 ,hence it is1
 no doubt1 that free hydrogen is not a  
constituent of the atmosphere of the    
,earth4  ,to what extent1 then1 has the 

atmosphere of ,mars fallen below its    
full proportion8 ,mr4 ,lowell has       
adopted an ingenious method of obtaining
 some light on this question1 by        
comparing the relative albedoes of the  
,earth and ,mars2 that is to say the    
relative power of reflection possessed  
by the two planets4 ,of course the      
method is rough2 we have first of all no
 satisfactory means of determining the  
albedo of the ,earth itself1 and ,mr4   
,lowell puts it higher than most        
astronomers would do2 then there is the 
difficulty of determining what portion  
of the total albedo is to be referred to
 the atmosphere and what to the actual  
soil or surface of the planet4 ,but1 on 
the whole1 ,mr4 ,lowell concludes that  
the amount of atmosphere above the unit 
of surface of ,mars is #j4bbb of that   
above the unit of surface of the ,earth4
 ,this would bring down the pressure on 
each square inch of ,mars to #a4b lb41  
and the aneroid barometer would read    
#b4e inches2 and water would boil at #dd

 deg4 ,c4 ,the range of temperature from
 day to night1 from summer to winter1 at
 any place on the planet would be       
increased1 while the range within which 
water could retain its liquid form would
 be diminished4  ,these statistics may  
seem rather dull and tiresome1 but if we
 are to deal with the problem before us 
at all1 it is important to understand   
that one factor in the condition of a   
planet cannot be altered and all the    
other factors retained unchanged4 ,it   
will be seen that in computing the      
density of the atmosphere of ,mars1 we  
had to take into consideration not only 
the diameter of the planet1 but the     
surface1 which varies as the square of  
the diameter2 the volume1 which varies  
as the cube2 the mass1 which varies in a
 higher power still2 and various        
combinations of these numbers4          
,novelists who write tales of journeys  
to other worlds or of the inhabitants of
 other worlds visiting this one1 usually
 assume that the atmosphere is of the   

same density on all planets1 and the    
action of gravity unchanged4 ,in their  
view it is only that men would have a   
little less ground to walk upon on      
,mars1 and a good deal more on ,jupiter4
 ,dean ,swift1 in ,gulliver's ,travels1 
made the ,lilliputians take a truer view
 of the effect of the alteration of one 
dimension1 for1 finding that ,gulliver  
was twelve times as tall as the average 
,lilliputian1 they did not appoint him  
the rations of twelve ,lilliputians1    
which would have been rather poor       
feeding for that veracious mariner1 but 
allotted him the cube of twelve1 viz4   
seventeen hundred and twenty-eight      
rations4 ,mr4 ,j4 ,holt ,schooling1 in  
one of his ingenious and interesting    
statistical papers1 tried to bring home 
the vast extent of the ,british ,empire 
by supposing that it seceded1 and taking
 the portion of ,earth that has fallen  
to it1 set up a world of its own--the   
planet ,victoria4 ,he allots to the     
,british ,empire #ba per cent of the    

land surface of the world4 ,if the      
,earth were divided so as to form two   
globes with surfaces in proportion of   
#ba to #gi1 the smaller globe1 which    
would correspond to ,mr4 ,schooling's   
new planet ,victoria1 would be less than
 half the present ,earth in diameter2 it
 would be considerably smaller than     
,mars4 ,but the rest of the world would 
be #j4if of the present ,earth in       
diameter1 or very nearly the size of    
,venus1 and it would contain just       
eight-ninths of the substance of the    
,earth1 leaving only one-ninth for      
,victoria4 ,the statistics given above  
will suggest to the reader that1 could  
such a secession be carried out1 the    
inhabitants of the ,british ,empire     
would not be happier for the change     
during the very short continued         
existence that remained to them4 ,the   
rest of the world could spare our       
fraction of the planet much better than 
we could spare theirs4  ,this is a      
principle which applies to worlds       

anywhere2 not merely within the limits  
of the solar system but wherever they   
exist4 ,everywhere the surface must vary
 with the square of the diameter2 the   
volume with the cube2 everywhere the    
smaller planet must have the rarer      
atmosphere1 and with a rare atmosphere  
the extreme range of temperature must be
 great1 while the range of temperature  
within which water will flow will be    
restricted4 ,our ,earth stands as the   
model of a world of the right size for  
the maintenance of life2 much smaller   
than our ,earth would be too small2 much
 larger1 as we shall see later1 would be
 too large4  ,so far we have dealt with 
,mars as if it received the same amount 
of light and heat from the ,sun that the
 ,earth does4 ,but1 as the ,table shows1
 from its greater distance from the     
,sun1 ,mars receives per unit of surface
 only about three-sevenths of the light 
and heat of that received by the ,earth4
  ,the inclination of the axis of ,mars 
is almost the same as that of the       

,earth1 so that the general character of
 the seasons is not very different on   
the two planets1 and the torrid1        
temperate1 and frigid zones have almost 
the same proportions4 ,the length of the
 day is also nearly the same for both1  
the ,martian day being slightly longer2 
but the most serious factor is the      
greater distance of ,mars1 and the      
consequent diminution in the light and  
heat received from the ,sun4 ,the light 
and heat received by the ,earth are not 
so excessive that we could be content to
 see them diminished1 even by #e per    
cent1 but for ,mars they are diminished 
by #eg per cent4 ,how can we judge the  
effect of so important a difference8    
,the mean temperature of our ,earth is  
supposed to be about #fj deg4,f41 or #af
 deg4,c4 ,three-sevenths of this would  
give us #g deg4,c4 as the mean          
temperature of ,mars1 which would       
signify a planet not impossible for     
life4 ,but the zero of the ,centigrade  
scale is not the absolute zero2 it only 

marks the freezing-point of water4 ,the 
absolute zero is computed to be -#bgc   
deg4 on the ,centigrade scale2 the      
temperature of the ,earth on the        
absolute scale therefore should be taken
 as #bhi deg41 and three-sevenths of    
this would give #abd deg4 of absolute   
temperature4 ,but this is #adi deg4     
below freezing-point1 and no life could 
exist on a planet under such conditions4
  ,but the mean temperature of ,mars    
cannot be computed quite so easily4 ,the
 hotter a body is the more rapidly it   
radiates heat2 the cooler it is the     
slower its radiation4 ,according to     
,stefan's ,law1 the radiation varies for
 a perfect radiator with the #dth power 
of the absolute temperature2 so that if 
,mars were at #abd deg4 abs41 while the 
,earth were at #bhi deg4 abs41 the      
,earth would be radiating its heat      
nearly #cj times faster than ,mars4 ,the
 heat income of ,mars would therefore be
 in a much higher proportion than its   
expenditure2 and necessarily its heat   

capital would increase until income and 
expenditure balanced4 ,prof4 ,poynting  
has made the temperature of the planets 
under the #dth power law of radiation   
the subject of an interesting enquiry1  
and the figures which he has obtained   
for ,mars and other planets are included
 in the ,table4  ,the equatorial and    
average temperatures are given under the
 assumption that ,mars possesses an     
atmosphere as efficient as our own in   
equalizing the temperature of the whole 
planet4 ,if1 on the other hand1 its     
atmosphere has no such regulating power1
 then under the zenith ,sun the upper   
limit of the temperature of a portion of
 its surface reflecting one-eighth would
 be1 as shown in the ,table1 #fd deg4,c4
 ,this would imply that the temperature 
on the dark side of the planet was very 
nearly at the absolute zero4 ,if we     
regard ,mars as resembling our ,moon1   
and take the ,moon's effective average  
temperature as #big deg4 abs41 the      
corresponding temperature for ,mars is  

#bdj deg4 abs41 and the highest         
temperature is four-fifths of #ccg deg4 
#bgj deg4 abs4 ,but the surface of ,mars
 has probably a higher coefficient of   
absorption than the surface of the      
,moon--it certainly has for light--so   
that we may put his effective average   
temperature1 on this supposition1 some  
few degrees above #bdj deg4 abs41 and   
his equatorial temperature some degrees 
higher still4 ,it appears as exceedingly
 probable1 then1 that whether we regard 
,mars as like the ,earth or1 going to   
the other extreme1 as like the ,moon1   
the temperature of his surface is       
everywhere below the freezing-point of  
water4#ad ,as the atmospheric           
circulation on ,mars must be languid1   
and the atmosphere itself is very rare1 
the general condition of the planet will
 approximate rather to the lunar type   
than to the terrestrial1 and the        
extremes1 both of heat and cold1 will   
approach those which would prevail on a 
planet without a regulating atmosphere4 

,there is another way of considering the
 effect on the climate of ,mars and its 
great distance from the ,sun1 which1    
though only rough and crude1 may be     
helpful to some readers4 ,if we take the
 ,earth at noonday at the time of the   
equinox1 then a square yard at the      
equator has the ,sun in its zenith1 and 
is fully presented to its light and     
heat4 ,but1 as we move away from the    
equator1 we find that each higher       
latitude is less fully presented to the 
,sun1 until1 when we reach latitude     
#fd-a_/b deg4--in other words just      
outside the ,arctic ,circle--#g square  
yards are presented to the ,sun so as to
 receive only as much of the solar      
radiation as #c square yards receive at 
the equator4 ,we may take1 then1        
latitude #fd-a_/b deg4 as representing  
,mars1 while the equator represents the 
,earth4 ,or1 we may take it that we     
should compare the climate of ,archangel
 with the climate of ,singapore4  ,now  
the mean temperature of latitude        

#fd-a_/b deg41 say the latitude of      
,archangel1 is just about freezing-point
 7#j deg4,c471 while that of the equator
 is about #bh deg4,c4 ,we should        
therefore expect from this a difference 
between the mean temperatures of the    
,earth and ,mars of #bh deg42 that is to
 say1 as the ,earth stands at #af       
deg4,c1 ,mars would be at -#ab deg4,c4  
,but1 on the ,earth1 the evaporation and
 precipitation is great1 and the        
atmospheric circulation vigorous4       
,evaporation is always going on in      
equatorial regions1 and the             
moisture-laden winds are continually    
moving polewards1 carrying with them    
vast stores of heat to be liberated as  
the rain falls4 ,the oceanic currents   
have the same effect1 and how great the 
modification which they introduce may be
 seen by comparing the climates of      
,labrador and ,scotland4 ,there appear  
to be no great oceans on ,mars4 ,the    
difference of #bh deg4 which we find on 
the ,earth between the equator and the  

edge of the ,arctic ,circle is a        
difference which remains after the      
convection currents of air and sea have 
done much to reduce the temperature of  
the equator and to raise that of high   
latitudes4 ,if we suppose that their    
effect has been to reduce this          
difference to one half of what it would 
have been were each latitude isolated   
from the rest1 we shall not be far      
wrong1 and we should get a range of #ef 
deg4 as the true equivalent difference  
between the mean temperatures of        
,singapore and ,archangel2 i4e4 of the  
,earth and ,mars2 and ,mars would stand 
at -#dj deg4,c4 ,the closeness with     
which this figure agrees with that      
reached by ,prof4 ,poynting suggests    
that it is a fair approximation to the  
correct figure4  ,the size of ,mars     
taught us that we have in it a planet   
with an atmosphere of but one half the  
density of that prevailing on the top of
 our highest mountain2 the distance of  
,mars from the ,sun showed us that it   

must have a mean temperature close to   
that of freezing mercury4 ,what chance  
would there be for life on a world the  
average condition of which would        
correspond to that of a terrestrial     
mountain top1 ten miles high and in the 
heart of the polar regions8 ,but ,mars  
in the telescope does not look like a   
cold planet4 ,as we look at it1 and note
 its bright colour1 the small extent of 
the white caps presumed to be snow1 and 
the high latitudes in which the dark    
markings--presumed to be water or       
vegetation--are seen1 it seems difficult
 to suppose that the mean temperature of
 the planet is lower than that of the   
,earth4 ,thus on the wonderful          
photographs taken by ,prof4 ,barnard in 
#aiji1 the ,nilosyrtis with the         
,protonilus is seen as a dark canal4    
,now the ,protonilus is in ,north ,lat4 
#db deg41 and on the date of            
observation--,september #bh1 #aiji--the 
winter solstice of the northern         
hemisphere of ,mars was just past4      

,there would be nothing unusual for the 
ground to be covered with snow and the  
water to be frozen in a corresponding   
latitude if in a continental situation  
on the ,earth4 ,then1 again1 in the     
summer1 the white polar caps of ,mars   
diminish to a far greater extent than   
the snow and ice caps of the ,earth2    
indeed1 one of the ,martian caps has    
been known to disappear completely4     
,yet1 as the accompanying diagram will  
show1 something of this kind is         
precisely what we ought to expect to    
see4 ,the diagram has been constructed  
in the following manner3 ,a curve of    
mean temperatures has been laid down for
 every #aj deg4 of latitude on the      
,earth1 derived as far as possible from 
accepted isothermals in continental     
countries in the northern hemisphere4   
,from this curve ordinates have been    
drawn at each #aj deg41 upward to show  
average deviation from the mean         
temperature for the hottest part of the 
day in summer1 downward for the         

deviation for the coldest part of the   
night in winter4 ,obviously1 on the     
average1 the range from maximum to      
minimum will increase from the equator  
to the poles4 ,the mean temperature of  
the ,earth has been taken as #af deg4,c1
 and as representing that prevailing in 
about #db deg4 lat4 ,the diagram shows  
that the maximum temperature of no place
 upon the ,earth's surface approaches   
the boiling-point of water1 and that it 
is only within the polar circle that the
 mean temperature is below              
freezing-point4 ,water1 therefore1 on   
the ,earth must be normally in the      
liquid state4  ,in constructing a       
similar diagram for ,mars1 three        
modifications have to be made4 ,first of
 all1 the mean temperature of the planet
 must be considerably lower than that of
 the ,earth4 ,next1 since the           
atmospheric circulation is languid and  
there are no great oceans1 the          
temperatures of different latitudes     
cannot be equalized to the same extent  

as on the ,earth4 ,it follows1          
therefore1 that the range in mean       
temperature from equator to pole must be
 considerably greater on ,mars than on  
the ,earth4 ,thirdly1 the range in      
temperature in any latitude1 from the   
hottest part of the day in summer to the
 coldest part of the night in winter1   
must be much greater than with us2      
partly on account of the very slight    
density of the atmosphere1 and partly on
 account of the length of the ,martian  
year4   ,illustration3 ,,thermographs   
,,of ,,the ,,earth ,,and ,,mars   ,we   
cannot know the exact figures to adopt1 
but the general type of the thermograph 
for ,mars as compared with that of the  
,earth will remain4 ,the mean           
temperature of ,mars will be lower1 the 
range of temperature from equator to    
pole will be greater1 and the extremes  
of temperature in any given latitude    
more pronounced than upon the ,earth4   
,and the general lesson of the diagram  
may be summed up in a sentence4 ,the    

maximum temperature on the planet is    
well above freezing-point1 and the part 
of the planet at maximum temperature is 
precisely the part that we see the best4
 ,but while this is so1 it is clear that
 water on ,mars must normally be in the 
state of ice2 ,mars is essentially a    
frozen planet2 and the extremes of cold 
experienced there1 not only every year  
but every night1 far transcend the      
bitterest extremes of our own polar     
regions4  ,the above considerations do  
not appear to render it likely that     
there is any vegetation on ,mars4 ,a    
planet ice-bound every night and with   
its mean temperature considerably below 
freezing-point does not seem promising  
for vegetation4 ,if vegetation exists1  
it must be of a kind that can pass      
through all the stages of its           
life-history during the few bright hours
 of the ,martian day4 ,every night will 
be for it a winter1 a winter of         
undescribable frost1 which it could only
 endure in the form of spores4 ,so if   

there be vegetation it must be confined 
to some hardy forms of a low type4 ,at a
 distance of forty millions of miles it 
is not easy to discriminate between the 
darkness of sheets of water and the     
darkness of stretches of vegetation4    
,some of the so-called seas may possibly
 be really of the latter class1 but that
 there must be expanses of water on the 
planet is clear1 for if there were no   
water surfaces there would be no        
evaporation2 and if there were no       
evaporation from whence could come the  
supply of moisture that builds up the   
winter pole cap8  ,the great ,american  
astronomer1 ,prof4 ,newcomb1 gave in    
,harper's ,weekly for ,july #be1 #aijh1 
an admirable summary of the verdict of  
science as to the character of the      
meteorology of ,mars4 ,the most careful 
calculation shows that if there are any 
considerable bodies of water on our     
neighbouring planet they exist in the   
form of ice1 and can never be liquid to 
a depth of more than one or two inches1 

and that only within the torrid zone and
 during a few hours each day4444 ,there 
is no evidence that snow like ours ever 
forms around the poles of ,mars4 ,it    
does not seem possible that any         
considerable fall of such snow could    
ever take place1 nor is there any       
necessity of supposing actual snow or   
ice to account for the white caps4 ,at a
 temperature vastly below any ever felt 
in ,siberia1 the smallest particles of  
moisture will be condensed into what we 
call hoar frost1 and will glisten with  
as much whiteness as actual snow4444    
,thus we have a kind of ,martian        
meteorological changes1 very slight     
indeed and seemingly very different from
 those of our earth1 but yet following  
similar lines on their small scale4 ,for
 snowfall substitute frostfall2 instead 
of feet or inches say fractions of a    
millimetre1 and instead of storms or    
wind substitute little motions of an air
 thinner than that on the top of the    
,himalayas1 and we shall have a general 

description of ,martian meteorology4    
,what we know of ,mars1 then1 shows us a
 planet1 icebound every night1 but with 
a day temperature somewhat above        
freezing-point4 ,as we see it1 we look  
upon its warmest regions1 and the       
rapidity with which it is cleared of    
ice1 snow1 and cloud shows the          
atmosphere to be rare and the moisture  
little in amount and readily evaporated4
 ,the seas are probably shallow         
depressions1 filled with ice to the     
bottom1 but melted as to their surfaces 
by day4 ,from the variety of tints noted
 in the seas1 and the recurrent changes 
in their outlines1 they are composed of 
congeries of shallow pools1 fed by small
 sluggish streams2 great ocean basins   
into which great rivers discharge       
themselves are quite unknown4           
,,chapter ,,viii  ,,the ,,illusions ,,of
 ,,mars   ,the two preceding chapters   
have led to two opposing1 two           
incompatible conclusions4 ,in ,chapter  
,,vi1 a summary was given of ,prof4     

,lowell's claim to have had ocular      
demonstration of the handiwork of       
intelligent organisms on ,mars4 ,in     
,chapter ,,vii1 it was shown that the   
indispensable condition for living      
organisms1 water in the liquid state1 is
 only occasionally present there1 the   
general temperature being much below    
freezing-point1 so that living organisms
 of high development and more than      
ephemeral existence are impossible4     
,prof4 ,lowell argues that the          
appearance of the network of lines and  
spots formed by the canals and oases1   
and its regular behaviour1 preclude its 
causation on such a scale by any natural
 process1 his assumption being that he  
has obtained finality in his seeing of  
the planet1 and that no improvement in  
telescopes1 no increase in experience1  
no better eyesight will ever break up   
the perfect regularity of form and      
position1 which he gives to the canals1 
into finer and more complex detail4     
,but the history of our knowledge of the

 planet's surface teaches us a different
 lesson4 ,two small objects appear      
repeatedly on the drawings made by ,beer
 and ,maedler in #ahcj2 these are two   
similar dark spots1 the one isolated1   
the other at the end of a gently curved 
line4 ,both spots resemble in form and  
character the oases of ,prof4 ,lowell1  
and the curved line1 at the termination 
of which one of the spots appears1      
represents closely the appearance       
presented by several of the canals4 ,in 
the year #ahcj no better drawings of    
,mars had appeared2 and in representing 
these two spots as truly circular and   
the curved line as narrow1 sharp1 and   
uniform1 ,beer and ,maedler undoubtedly 
portrayed the planet as actually they   
saw it4 ,the one marking was named by   
,schiaparelli the ,lacus ,solis1 the    
other1 the ,sinus ,sabaeus1 and they are
 two of the best known and most easily  
recognized of the planet's features2 so 
that it is easy to trace the growth of  
our knowledge of both of them from #ahcj

 up to the present time4 ,they were     
drawn by ,dawes in #ahfd1 by            
,schiaparelli in #ahgg and the          
succeeding years1 by ,lowell in #ahid   
and since1 and by ,antoniadi in #aiji   
and #aiaa4 ,but whereas the drawings of 
,beer and ,maedler1 made by the aid of a
 telescope of #d inches aperture1 show  
the two spots as exactly alike1 in those
 of ,dawes1 made with a telescope of #h 
inches1 the resemblance between the two 
has entirely vanished1 and neither is   
shown as a plain circular dot4 ,since   
then1 observers of greater experience   
and equipped with more powerful         
instruments have directed their         
attention to these two objects1 and a   
mass of complicated structure has been  
brought out in the regions which were so
 simple in the sight of ,beer and       
,maedler1 so that not a trace of        
resemblance remains between the two     
objects that to them appeared           
indistinguishable4  ,now the gradation  
in size1 from the ,lacus ,solis down to 

the smallest oasis of ,lowell1 is a     
complete one4 ,if a future development  
in the power of telescopes should equal 
the advance made from the #d-;inch of   
,beer and ,maedler1 to the #cc-;inch    
which ,antoniadi used in #aiji1 is it   
reasonable to suppose that ,prof4       
,lowell's oases will refuse to yield to 
such improvement1 and will all still    
show themselves as uniform spots1       
precisely circular in outline8 ,it is   
clear that ,beer and ,maedler would have
 been mistaken if they had argued that  
the apparently perfect circularity of   
the two oases which they observed proved
 them to be artificial1 because the     
increase in telescopic power has since  
shown us that neither is circular4 ,the 
obvious reason why they appeared so     
round to ,beer and ,maedler was that    
they were too small to be defined in    
their instruments2 their minor          
irregularities were therefore invisible1
 and their apparent circularity covered 
detail of an altogether different form4 

,beer and ,maedler only drew two such   
spots2 ,lowell shows about two hundred4 
,beer and ,maedler's two spots seemed to
 them exactly alike2 these two spots as 
we see them to-day have no resemblance  
to each other4 ,prof4 ,lowell's two     
hundred oases1 with few exceptions1 seem
 all of the same character2 is it       
possible to suppose1 if telescopes      
develop in the future as they have done 
in the past1 that the two hundred oases 
will preserve their uniformity of       
appearance any more than the ,lacus     
,solis and the head of the ,sinus       
,sabaeus8 ,if a novice begins to work   
upon ,mars with a small telescope1 he   
will draw the ,lacus ,solis and the     
,sinus ,sabaeus as two round1 uniform   
spots1 and as he gains experience1 and  
his instrumental power is increased1 he 
will begin to detect detail in them1 and
 draw them as ,dawes and ,schiaparelli  
and others have shown them later4 ,it is
 no question of planetary change2 it is 
a question of experience and of seeing4 

,there is a much simpler explanation of 
the regularity of the canals and oases  
than to suppose that an industrious     
population of geometers have dug them   
out or planted them2 it is connected    
with the nature of vision4  ,a telegraph
 wire seen against a background of a    
bright cloud can be discerned at an     
amazing distance--in fact1 at #bjj1jjj  
times the breadth of the wire2 a        
distance at which the wire subtends a   
breadth of a second of arc4 ,for average
 normal sight the perception of the wire
 will be quite unmistakable1 but at the 
same time it would be quite untrue to   
say that the perception of the wire was 
of the nature of defined vision1 as     
would be seen at once if small objects  
of irregular shape were threaded on the 
wire2 these would have to be many times 
the breadth of the wire in order to be  
detected4 ,again1 if instead of a wire  
of very great length extending right    
across the field of view of both eyes1 a
 short1 black line be drawn on a white  

ground1 it will be found that as the    
length of the line is diminished below a
 certain point so its breadth must be   
increased4 ,if the observer is distant  
from the line #fjjj times its length1   
then the breadth must be increased to be
 equal to the length1 and the object1   
whatever its actual shape1 can be just  
recognized as a small circular spot1    
which will subtend about #cd seconds of 
arc4  ,but though a black spot1 #cd     
seconds in diameter1 can be perceived on
 a white ground1 we have not yet        
attained to defined vision4 ,for if we  
place two black spots each #cd seconds  
of arc in diameter1 near each other1    
they will not be seen as separate spots 
unless there is a clear space between   
them of six times that amount4 ,nearer  
than that they will give the impression 
that they form one circular spot1 or an 
oval one1 or even a uniform straight    
line1 according to the amount of        
separation4 ,if two equal round spots be
 placed so that the distance between    

their centres is equal to two diameters1
 then the diameter of each spot must be1
 at least1 #gj seconds of arc for them  
to be distinctly defined2 that is to say
 for the spots to be seen as two        
separate objects4  ,it will be seen that
 there is a wide range between objects  
that are large enough to be quite       
unmistakably perceived1 and objects     
which are large enough to have their    
true outline really defined4 ,it is a   
question of seconds of arc in the one   
case and of minutes of arc in the other4
 ,within this range1 between the limit  
at which objects can be just perceived  
and that where they can be just defined1
 objects must all appear as of one of   
two forms--the straight line and the    
circular dot4  ,this depends upon the   
structure of the eye and of the retina2 
the eye being essentially a lens with   
its defining power necessarily limited  
by its aperture1 and the retina a       
sensitive screen built up of an immense 
number of separate elements each of     

which can only transmit a single        
sensation4 ,different eyes will have    
different limits1 both for the smallest 
objects which can be discerned and for  
the smallest objects that can be        
defined1 but for any sight the range    
between the two will be of the order    
just indicated4  ,prof4 ,lowell has     
drawn attention to the strangely        
economic character of both the canals   
and oases in the matter of form4 ,it is 
true that straight lines and circles are
 economic forms1 but they are economic  
not only in the construction of         
irrigation works but also in vision4    
,the circle is the figure which encloses
 the maximum area for the minimum       
average distance from its centre to any 
point situated within it2 therefore1 if 
a small spot be perceived by the sight  
but be too small to have its actual     
outline defined1 it will be recognized  
by the eye as being truly circular1 on  
the principle of economy of effort4 ,so1
 again1 a straight line is the shortest 

that can be drawn between two points2   
and a straight line can be perceived as 
such when of an angular breadth quite   
#dj times less than that of the smallest
 spot4 ,a straight line is that which   
gives the least total excitement in     
order to produce an appreciable         
impression1 and therefore the smallest  
appreciable impression produces the     
effect of a straight line4  ,it is      
sufficient1 then1 for us to suppose that
 the surface of ,mars is dotted over    
with minute irregular markings1 with a  
tendency to aggregate in certain        
directions1 such as would naturally     
arise in the process of the cooling of a
 planet when the outer crust was        
contracting above an unyielding nucleus4
 ,if these markings are fairly near each
 other it is not necessary1 in order to 
produce the effect of canals1 that they 
should be individually large enough to  
be seen4 ,they may be of any conceivable
 shape1 provided that they are          
separately below the limit of defined   

vision1 and are sufficiently sparsely   
scattered4 ,in this case the eye        
inevitably sums up the details 7which it
 recognizes but cannot resolve7 into    
lines essentially canal-like in         
character4 ,wherever there is a small   
aggregation of these minute markings1 an
 impression will be given of a circular 
spot1 or1 to use ,prof4 ,lowell's       
nomenclature1 an oasis4 ,if the         
aggregation be greater still and more   
extended1 we shall have a shaded area--a
 sea4  ,the above remarks apply to      
observation with the unaided eye1 but   
the same principle applies yet more     
strongly to telescopic vision4 ,no star 
is near enough or sufficiently large to 
give the least impression of a true     
disc2 its diameter is indistinguishable2
 it is for us a mathematical point1     
without parts or magnitude4 ,but the    
image of a star formed by a telescope is
 not a point but a minute disc1         
surrounded by a series of diffraction   
rings4 ,this disc is spurious1 for the  

greater the aperture of the telescope   
the smaller the apparent disc4  ,that   
which holds good for a bright point like
 a star holds good for every individual 
point of a planetary surface when viewed
 through the telescope2 that is to say1 
each point is represented by a minute   
disc2 all lines and outlines therefore  
are slightly blurred1 so that minute    
irregularities are inevitably smoothed  
out4  ,when we come to photographs1 the 
process is carried to a third stage4    
,the image is formed by the telescope1  
subject to all the limitations of       
telescopic images1 and is received on a 
plate essentially granular in structure1
 and is finally examined by the eye4    
,the granular structure of the plate    
acts as the third factor in concealing  
irregularities and simplifying details2 
a third factor in producing the two     
simplest types of form--the straight    
line and the circular dot4  ,prof4      
,lowell describes the canals as like    
lines drawn with pen1 ink and ruler1 but

 not a few of our best observers have   
advanced much beyond this stage4 ,even  
as far back as #ahhd1 some of the canals
 were losing their strict rectilinear   
appearance to ,schiaparelli1 and the    
observers of the planet who have been   
best favoured by the power of the       
telescope at their disposal1 by the     
atmospheric conditions under which they 
worked1 and by their own skill and      
experience--such as ,antoniadi1         
,barnard1 ,cerulli1 ,denning1           
,millochau1 ,molesworth1 ,phillips1     
,stanley ,williams and others--have     
found them to show evident signs of     
resolution4 ,thus1 in #aiji1 ,antoniadi 
found that of #ej canals1 #ad were      
resolved into disconnected knots of     
diffused shadings1 #d were seen as      
irregular lines1 #aj as more or less    
dark bands2 and he found that1 in good  
seeing1 there was no trace whatever of  
the geometrical network4  ,the progress 
of observation1 therefore1 has left     
,prof4 ,lowell behind1 and has dispelled

 the fable which he has defended with so
 much ingenuity4 ,but1 indeed1 there    
never was any more reason for taking    
seriously his theory as to the presence 
of artificial waterways on ,mars than   
for believing in the actual existence of
 the weird creatures described by ,h4   
,g4 ,wells in the ,war of the ,worlds4  
,there are too many oversights in the   
canal theory4  ,thus no source is       
indicated for the moisture supposed to  
be locked up in the winter pole cap4    
,prof4 ,lowell holds that there are no  
large bodies of water on the planet2    
that the so-called seas are really      
cultivated land4 ,in this case there    
could be little or no evaporation1 and  
so no means by which the polar deposits 
could be recruited4  ,yet it is certain 
that the supply of the winter pole cap  
must come from the evaporation of water 
in some region or other4 ,and here is   
another oversight of the artificial     
canal theory4 ,the canals are supposed  
to be necessary for the conveyance of   

water from the pole towards the equator2
 although1 as this was uphill1 vast     
pumping stations at short intervals had 
to be predicated4 ,but it is not        
supposed that the water needed to travel
 by way of the canals to the poles4 ,if1
 however1 the moisture is conveyed as   
vapour through the atmosphere to the    
pole as winter approaches1 it cannot be 
impossible that it should be conveyed in
 the same manner from the pole as summer
 draws on1 and in that case the         
artificial canals would not be needed4  
,if the canals are necessary for        
conveying the water in one direction1   
they would be necessary for the opposite
 direction4 ,but there would be         
something too farcical in the idea of   
the careful ,martians dispatching their 
water first to the pole to be frozen    
there1 and then1 after it had been duly 
frozen and melted again1 fetching it    
back along thousands of miles and       
through numerous pumping stations for   
use in irrigating their fields4  ,of all

 the many hundreds of canals only a few 
actually touch the polar caps4 ,but on  
the theory that the entire canal system 
is fed by the polar cap in summer1 the  
carrying capacity of the polar canals   
should be equal to1 if not greater than1
 that of the entire system outside the  
polar circle4 ,a glance at the charts of
 the planet shows that the polar canals 
could not supply a twentieth part of the
 water needed for those in the          
equatorial regions4 ,another oversight  
is that of the significance of the      
alleged uniformity and breadth of the   
canals4 ,prof4 ,lowell repeatedly       
insists that the canals are of even     
breadth from end to end1 and spring into
 existence at once throughout their     
whole length4 ,this statement is in     
itself a proof that the canals cannot be
 what he supposes them to be4 ,an       
irrigation system could not have these  
characteristics2 the region fertilized  
would take time to develop2 we should   
see the canal extending itself gradually

 across the continent1 and its breadth  
would not be uniform from end to end1   
but the region fertilized would grow    
narrower with increase of distance from 
the fountain head of the canal4  ,under 
what conditions can we see straight     
lines1 perfectly uniform from end to    
end1 spring into existence1 in their    
entirety1 without going through any     
stages of growth8 ,when the lines are   
not actual images1 but are suggested by 
markings perceived1 but not perfectly   
defined4 ,in #aijb and #aijc1 in        
conjunction with ,mr4 ,evans1 the       
headmaster of ,greenwich ,hospital      
,school1 ,i tried a number of           
experiments on this point1 with the aid 
of about two hundred of the boys of the 
school4 ,they had several qualifications
 in respect of these experiments2 they  
were keen-sighted1 well drilled2        
accustomed to do what they were told    
without asking questions2 and they knew 
nothing whatsoever of astronomy1        
certainly nothing about ,mars4  ,a      

diagram was hung up1 based upon some    
drawing or other of the planet made by  
,schiaparelli1 ,lowell or other ,martian
 observer1 but the canals were not      
inserted2 only a few dots or irregular  
markings were put in here and there4    
,and the boys were arranged at different
 distances from the diagram and told to 
draw exactly what they saw4 ,those      
nearest the diagram were able to detect 
the little irregular markings and       
represented them under their true forms4
 ,those at the back of the room could   
not see anything of them1 and only      
represented the broadest features of the
 diagram1 the continents and seas4      
,those in the middle of the room were   
too far off to define the minute        
markings1 but were near enough for those
 markings to produce some impression    
upon them2 and that impression always   
was of a network of straight lines1     
sometimes with dots at the points of    
meeting4 ,advancing from a distance     
toward the diagram the process of       

development became quite clear4 ,at the 
back of the room no straight lines were 
seen2 as the observer came slowly       
forward1 first one straight line would  
appear completely1 then another1 and so 
on1 until all the chief canals drawn by 
,schiaparelli and ,lowell in the region 
represented had come into evidence in   
their proper places4 ,advancing still   
further1 the canals disappeared1 and the
 little irregular markings which had    
given rise to them were perceived in    
their true forms4  ,these experiments at
 the ,greenwich ,hospital ,school were  
merely the repetition of similar ones   
that ,i had myself made privately twelve
 years earlier1 leading me to the       
conclusion1 published in #ahid1 that the
 canals of ,mars were simply the        
summation of a complexity of detail too 
minute to be separately discerned4  ,a  
little later1 in his work ,marte nel    
#ahif-g1 ,dr4 ,cerulli independently    
arrived at the same conclusion1 and     
wrote3 ,these lines are formed by the   

eye 444 which utilizes 444 the dark     
elements which it finds along certain   
directions2 and a large number of these 
elements forms a broad band2 and a      
smaller number of them gives rise to a  
narrow line4 ,also1 the marvellous      
appearance of the lines in question has 
its origin1 not in the reality of the   
thing1 but in the inability of the      
present telescope to show faithfully    
such a reality4 ,in #aijg1 ,prof4       
,newcomb made some experiments in the   
same direction and reached the same     
general conclusion4 ,more recently      
still1 ,prof4 ,w4 ,h4 ,pickering has    
worked on the same lines and with the   
same result4 ,the venerable ,george     
,pollock1 formerly the ,senior ,master  
of the ,supreme ,court and ,king's      
,remembrancer1 sent to me1 in his #iast 
year1 the following note as affording an
 apt illustration of the true nature of 
the canaliform markings on ,mars3  ,on  
,saturday last1 journeying in a         
motor-car1 ,i came into a broad road    

bounded by a dark wood4 ,looking up ,i  
was amazed to see distinct1             
well-defined1 vertical1 parallel white  
lines1 the wood forming the dark        
background4 ,on getting nearer1 these   
lines resolved themselves into spots1   
and they proved to be the white         
insulators supporting the telegraph     
wires4  ,prof4 ,lowell has objected that
 all experiments and illustrations of   
this kind are irrelevant2 only          
observations upon the planet itself     
ought to be taken into account4  ,but   
such observations have been made upon   
the planet itself with just the same    
result4 ,observers have seen streaks    
upon ,mars--knotted1 broken1 irregular1 
full of detail--and when the planet has 
receded to a greater distance1 the very 
same marking has shown itself as a      
narrow straight line1 uniform from end  
to end1 as if drawn with pen1 ink and   
ruler4 ,the greater distance has caused 
the irregularities1 seen when nearer at 
hand1 to disappear4 ,in this1 and not in

 any gigantic engineering works1 is the 
explanation of the artificiality of the 
markings on ,mars as ,prof4 ,lowell sees
 them4 ,that artificiality has already  
disappeared under better seeing with    
more powerful telescopes4  ,this chapter
 is entitled ,the ,illusions of ,mars4  
,yet the illusions of ,mars are not the 
straight lines and round dots of the    
canal system1 but the forced and curious
 interpretation which has been put upon 
them4 ,if the planet be within a certain
 range of distance and under examination
 with a certain telescopic power1 the   
straight lines and round dots are       
inevitable4 ,their artificiality is not 
a function of the actual ,martian       
details themselves1 but of the mode in  
which1 under given conditions1 we are   
obliged to see them4     ,,chapter ,,ix 
,,venus1 ,,mercury ,,and ,,the          
,,asteroids   ,of all the planets1      
,venus appears1 to the unassisted eye1  
by far the loveliest4 ,when seen in the 
early morning before sunrise--its       

western elongation--or after sundown in 
the evening--its eastern elongation--and
 still more as it attains its greatest  
brilliancy1 it has attracted attention  
everywhere and in all ages4 ,it then    
shines with brilliance ten times as     
great as ,jupiter in opposition1 and the
 brightest members of the heavenly host 
look pale and dim beside it4 ,it is     
emphatically the morning or the evening 
star1 ,lucifer1 or ,vesper1 herald or   
follower of the ,sun2 it can even assert
 itself in the presence of the ,lord of 
,day1 for it has often been seen at     
noonday by watchers who knew where to   
look2 sometimes by the general crowd4   
,but in the telescope ,venus appears    
less satisfying4 ,it is a pretty        
spectacle indeed to watch the phases of 
the gleaming little globe of silver1    
for1 like the ,moon under varying       
illumination from the ,sun1 it undergoes
 change of apparent shape4 ,but the     
surface of the planet yields little     
detail1 and that little is illusive and 

ill-defined4 ,the clear-cut outlines and
 black shadows of the ,moon have no     
place here1 nor do the ruddy plains and 
blue-grey seas of ,mars find any        
analogues4 ,all that can be observed    
beyond the changes of phase are a few   
faint1 ill-defined patches1 where the   
molten silver of the general surface is 
slightly dimmed and tarnished1 and      
perhaps one or two spots1 not less      
evasive and difficult to fix1 that      
exceed the rest of the surface in       
brightness4  ,this very difficulty in   
making out the markings on ,venus is    
hopeful for our search2 it points to a  
veiling over the planet1 a veiling by an
 atmosphere4 ,and the statistics of the 
,table show that ,venus closely         
resembles our ,earth in size and mass1  
and therefore probably in atmospheric   
equipment4 ,if we assume that the       
atmosphere of any planet is in direct   
proportion to its mass--and as ,venus is
 so nearly the twin of the ,earth there 
is no reason to expect any great        

difference between the two in this      
respect--the atmosphere of ,venus would 
have a pressure of about #aa4b lb4 on   
the square inch1 and the level of half  
pressure would be nearly four miles     
above the surface4 ,in other words the  
atmosphere would be both thinner and    
deeper than that of the ,earth1 but the 
difference would not be important in    
amount4  ,but ,venus is nearer to the   
,sun than the ,earth1 and receives      
nearly double the light and heat4 ,its  
theoretical equatorial temperature is   
#cfh deg4abs41 or #ie deg4,c1 and its   
corresponding mean temperature is #fi   
deg4 ,c4 ,but water under a pressure of 
#aa4b lb4 will boil at #ic deg4 ,c1 so  
that at the equator of ,venus the upper 
limit for water as a liquid is just     
passed1 but1 for the planet in general1 
a fairly safe margin is maintained4     
,here then is sufficient explanation why
 the topography of ,venus is concealed4 
,the atmosphere will always be          
abundantly charged with water-vapour1   

and an almost unbroken screen of clouds 
be spread throughout its upper regions4 
,such a screen will greatly protect the 
planet from the full scorching of the   
,sun1 and tend to equalize the          
temperature of day and night1 of summer 
and winter1 of equator and poles4 ,the  
temperature range will be slight1 and   
there will be no wide expanses of polar 
ice4 ,water that flows will be abundant 
everywhere4  ,so far all the facts      
connected with ,venus are favourable for
 life1 even though the picture called up
 to the mind may not seem inviting to   
us4 ,for views of the heavens must be   
rare2 the ,sun must seldom pierce       
through the cloud veil2 there is no moon
 and the stars must be almost always    
hidden4 ,the ,earth with its ,moon might
 form a beautiful ornament at times in  
the midnight sky if the cloud-shell     
should occasionally open1 but on the    
whole1 the planet is shut up to itself  
in a perpetual vapour-bath1 and its     
condition will approach that of some of 

the most humid countries in the         
terrestrial tropics during the height of
 their rainy seasons4  ,but it would    
seem that life both of plants and       
animals1 under such conditions1 might   
flourish and be abundant4 ,the mean     
temperature would not1 in general1 be   
high enough to drive off the water as   
steam1 nor low enough to congeal it into
 ice2 it would remain water--water that 
flows4  ,but there is still a possible  
hindrance to life on ,venus1 a hindrance
 that actually exists in the case of    
,mercury4  ,mercury1 the ,twinkler1 is  
not an easy object in our ,northern     
latitudes1 but1 in countries near the   
tropics1 is often quite conspicuous1 a  
little scintillating gem of light in the
 bright sky1 before sunrise or after    
sunset4 ,in the telescope it is not so  
attractive as ,venus1 partly because it 
is smaller1 partly because1 though it   
receives more than three times as much  
light from the ,sun1 it is duller in    
hue4 ,yet it is not quite so secretive  

as its neighbour1 and a certain number  
of markings have been detected upon its 
disc1 markings which1 like those of the 
,moon1 appear to be permanent4  ,a      
glance at the ,table will show that this
 was to be expected4 ,in size1 ,mercury 
comes between the ,moon and ,mars1 and  
the atmospheric veil ought therefore to 
be1 as it evidently is1 very slight and 
transparent2 offering little or no      
hindrance to an observer scanning it    
from another world4 ,the other necessary
 consequences of small size and mass    
will follow2 the feeble force of        
gravitation1 the languid atmospheric    
circulation1 the extreme range of       
temperatures1 the low temperature at    
which water will boil4  ,but the heat to
 which ,mercury is exposed far          
transcends our terrestrial experience4  
,in the mean it receives nearly seven   
times as much heat from the ,sun as the 
,earth does1 but this supply is not     
maintained uniformly1 for ,mercury moves
 round the ,sun in a very eccentric     

orbit1 so that when in aphelion it      
receives1 surface for surface1 only     
about four times as much heat as the    
,earth1 but some six weeks later when in
 perihelion it receives more than eleven
 times4 ,the great range of temperature 
due to the thinness of the atmosphere   
must therefore be further increased by  
the varying distance of the planet from 
the ,sun4  ,a reference to ,prof4       
,poynting's figures shows that the mean 
temperature of ,mercury must approximate
 to #aid deg4 ,c41 while water will boil
 at #dj deg4 ,c4 or even lower4 ,here1  
then1 is a condition the exact reverse  
of ,mars4 ,water as a liquid will be    
rare on ,mercury1 not because it is     
congealed1 but because it is evaporated2
 on the dark side of the planet it may1 
indeed1 pass into ice1 but on the side  
exposed to the ,sun it must exist       
normally as a constituent of the        
atmosphere4 ,water in a liquid state1   
water that flows1 must be almost        
unknown4  ,but we have good reason to   

believe that that which is the dark side
 of ,mercury at one time is always dark2
 that which is exposed to the ,sun is   
always exposed to it4  ,since ,mercury  
wears no concealing veil of atmosphere1 
and displays markings that can be       
identified and followed1 a surprising   
circumstance has come to light4 ,in     
#ahhi1 ,schiaparelli discovered that    
,mercury1 instead of rotating on its    
axis in about #bd hours like the ,earth 
and ,mars1 rotates in #hh days2 that is 
to say1 it always turns the same face   
towards the ,sun1 just as the ,moon     
turns the same face towards the ,earth4 
,this fact1 confirmed theoretically by  
,prof4 ,g4 ,h4 ,darwin in his           
development of the theory of tidal      
friction1 puts the condition of ,mercury
 in quite a new light4 ,no alternation  
of day or night refreshes and restores  
the little world2 one hemisphere is for 
ever exposed to the blasting heat of the
 ,sun1 seven times hotter for it than   
for the ,earth2 the other hemisphere is 

for ever exposed to the darkness and    
cold of outer space1 a range from       
something like #cij deg4 ,c4 above      
freezing-point1 to #bgj deg4 ,c4 below4 
,it is true that between the two        
hemispheres there is a debatable land1  
for1 owing to the ellipticity of the    
orbit1 the face turned to the ,sun is   
not exactly the same at all times1 and a
 region about #dg deg4 in width on each 
side of the planet1 that is to say1     
rather more than a quarter of its entire
 surface1 has one day and one night in  
each period of #hh days1 but these more 
favoured sections can scarcely be       
considered more habitable than the rest4
  ,the conditions of ,mercury are so    
unfavourable for life that1 even if this
 remarkable relation of rotation period 
to revolution did not hold good1 it     
would still be impossible to regard it  
as a world for habitation4 ,but its case
 shows that a further condition of      
habitability has to be satisfied by a   
planet4 ,size and distance from the ,sun

 afford the first two conditions2 a     
suitable rotation period is now seen to 
be a third4  ,and it is possible that in
 this very particular ,venus fails to   
qualify4 ,schiaparelli1 the first       
observer of his time1 assisted by the   
clear ,italian sky1 believed that he had
 demonstrated that ,venus1 like         
,mercury1 rotates once in her year2 her 
day being thus equal in length to #bbe  
of ours1 and the face that she turns to 
the ,sun being always the same4  ,and in
 her case this statement requires       
practically no qualification1 for1 her  
orbit being nearly circular1 there is   
hardly any libration2 a place that has  
the ,sun in its zenith has it so for    
ever2 one on the night side of ,venus   
can never have a sunrise1 or gladden in 
the daylight4 ,the side exposed to the  
,sun will wither in a temperature of    
about #bbg deg4 ,c41 in which all       
moisture will be evaporated2 the side   
remote from it will be bound in eternal 
ice4 ,in neither hemisphere will water  

exist in the liquid state2 in neither   
hemisphere will life be possible4  ,but 
as yet the evidence is not conclusive   
that ,venus has this long rotation      
period4 ,several observers of high rank 
believe that our neighbour rotates in   
nearly the same time as the ,earth1 but 
its markings are so faint and elusive   
that the problem is a difficult one4    
,the spectroscopic method of determining
 the speed of rotation has been equally 
indecisive4 ,until1 therefore1 the      
rotation period has been decided1 the   
habitability of ,venus must remain in   
question4 ,if it always turns the same  
face to the ,sun1 there can be no more  
life upon it than upon ,mercury2 if on  
the contrary it rotates in much the same
 time as the ,earth1 then1 so far as we 
know1 it may well be a habitable world4 
,whether it is actually inhabited is a  
matter at present entirely beyond our   
knowledge4  ,a page or two back we      
touched lightly on the eccentricity of  
the orbit of ,mercury--lightly1 because 

it was not the chief factor in disabling
 the planet for habitation4 ,but the    
condition introduced by this            
eccentricity is one which of itself     
would be sufficient to put it out of    
court4 ,in the six weeks in which       
,mercury moves from aphelion to         
perihelion1 it approaches the ,sun by   
fourteen millions of miles1 and the heat
 received by it is increased #b-a_/b    
times4 ,then1 in the next six weeks1 it 
recedes as far1 and there is a like     
diminution4 ,in other words1 six weeks  
makes a greater proportional change in  
this one planet's condition than we     
should experience if our ,earth were    
transported from its own orbit to that  
of ,mars4  ,but there are other members 
of the solar system whose orbits are so 
elongated that that of ,mercury seems in
 comparison almost circular4 ,these are 
the comets1 some of which all but graze 
the surface of the ,sun at perihelion1  
and then recede from him for periods    
that it takes even thousands of years to

 complete4 ,but without dwelling on such
 extreme cases1 two of the best known of
 the periodic comets may be taken as    
examples of the rest4 ,encke's is the   
comet of shortest period1 returning in  
about #c4c years4 ,at perihelion it is  
#ca millions of miles from the ,sun2    
one-third the distance of the ,earth4   
,it receives1 therefore1 at this part of
 its orbit1 #i times as much light and  
heat as the ,earth4 ,but at aphelion it 
retreats deep into the region of the    
asteroids1 and is much more than four   
times the mean distance of the ,earth4  
,at this part of its orbit it receives  
but #a_/agth as much heat as the ,earth4
 ,by far the most famous of all the     
comets is that known by the name of     
,halley1 and its mean period is #gf     
years4 ,at perihelion it comes within   
the orbit of ,venus2 indeed1 nearly     
halfway between that and the orbit of   
,mercury4 ,at aphelion it recedes to    
thirty-five times the distance of the   
,earth1 far beyond the orbit of         

,neptune4 ,the range in its light and   
heat from the ,sun is from #c times that
 of the ,earth to less than #a_/abjjth2 
or1 in other words1 the supply of heat  
at one time is nearly #djjj times that  
at another1 and of the #gf years of its 
period1 only #hj days are spent within  
the orbit of the ,earth4  ,comets cannot
 be homes of life2 they are not         
sufficiently condensed2 indeed1 they are
 probably but loose congeries of small  
stones4 ,but even if comets were of     
planetary size it is clear that life    
could not be supported on them2 water   
could not remain in the liquid state on 
a world that rushed from one such       
extreme of temperature to another4      
,between the orbits of ,mars and        
,jupiter there are scattered an untold  
number of little planets commonly known 
as asteroids or minor planets4 ,minor   
planets indeed they are1 for the one    
first discovered--,ceres-- probably     
outweighs all the rest1 known and       
unknown1 put together1 though something 

like #gjj have already been detected1   
and the list grows at the rate of about 
one a week4  ,as the ,table shows1      
,ceres is so small that the ,earth      
exceeds it in volume #ejjj times2 even  
the ,moon is #ij times as large4 ,the   
mass of ,ceres is not known2 being so   
small1 its density is probably less than
 that of the ,moon1 so that the ,earth  
may easily outweigh it #aj1jjj times4   
,the unfavourable conditions resulting  
from smallness of size that the ,moon   
presents are therefore exaggerated      
exceedingly in the case of ,ceres2 its  
atmosphere must approach in tenuity what
 we should regard as a vacuum in a      
terrestrial laboratory1 and water as a  
liquid be entirely unknown4 ,its        
distance from the ,sun is another       
hostile factor2 for in consequence it   
receives per unit of surface only #ac   
per cent of the light and heat that     
falls on the ,earth2 its maximum        
temperature under a zenith ,sun will    
fall far below freezing-point1 the      

minimum on the dark side will approach  
the absolute zero4  ,with ,ceres the    
whole of the asteroidal family can be   
dismissed as possible abodes of life4   
,no astronomer can regard them as such4 
,yet they have their lesson to teach4   
,life can exist on the ,earth only on   
the upper face of its crust1 and in a   
very thin film of air and water2 but the
 enormous solid bulk within1 inert      
though it be1 that supports the stage on
 which the great drama of life is       
played1 is as really essential as air   
and water themselves4 ,if that bulk were
 much smaller and less massive life     
could find no place upon its surface4   
,,chapter ,x  ,,the ,,major ,,planets   
,it is a striking change to pass from   
,ceres1 the giant of the minor planets1 
to ,jupiter1 the giant of the major     
planets4 ,instead of a world that the   
,earth exceeds in volume #ejjj times1 we
 are confronted by one that exceeds the 
,earth #adjj times4 ,ceres1 when viewed 
through a large telescope1 is just able 

to present a perceptible disc2 ,jupiter 
offers the largest shown by any heavenly
 body after the ,sun and ,moon4  ,and   
that disc is one that never fails to    
charm the attentive student1 for it     
abounds in colour1 movement and change4 
,the late ,prof4 ,james ,keeler1 an     
observer of the first rank1 having the  
advantage of observing the planet from  
the summit of ,mt4 ,hamilton and with   
the great #cf-;inch telescope of the    
,lick ,observatory1 thus describes the  
aspect of the planet in #ahhi4          
,seen with this instrument on a fine    
night1 the disc of ,jupiter was a       
most beautiful object1 covered with a   
wealth of detail which could not        
possibly be accurately represented in a 
drawing4444 ,scarcely any     portion of
 ,jupiter1 except the ,red ,spot and the
 extreme polar regions1     was of a    
uniform tint1 the surface being mottled 
with flocculent and     more or less    
irregular cloud masses4444 ,the         
equatorial zone1 occupying     the space

 between the red belts1 was marked in   
the centre by a     salmon-coloured     
stripe1 which was occasionally          
interrupted by an     extension of the  
white clouds on the sides of the zone4  
,the edges were     brilliant white1 and
 were formed of rounded cloud-like      
masses1 which     at certain places     
extended into the red belts as long     
streamers4444     ,near their junction  
with the equatorial zone1 the streamers 
were white     and definite in outline1 
but they became redder in tint toward   
their     outer extremities1 and more   
diffuse1 until they were lost in the    
general red colour of the background4   
,when the seeing was good they     were 
seen to be formed of irregular rounded  
or feathery clouds1 fading     toward   
the outer ends1 until the structure     
could no longer be     distinguished4444
 ,the portions of the equatorial zone   
surrounding the     roots of well-marked
 streamers were somewhat brighter than  
at other     places1 and it is a curious

 circumstance that they were almost     
invariably suffused with a pale         
olive-green colour1 which seemed to be  
associated with great disturbance1 and  
which was rarely seen     elsewhere4444 
,the red belts presented on all         
occasions the appearance     of a       
passive medium1 in which the phenomena  
of the streamers and other     forms 444
 were manifested4 ,the phenomena would  
be exactly reproduced     by streamers  
of cloudy white matter floating in a    
semi-transparent     reddish fluid1     
sometimes submerged and sometimes rising
 to the     surface4444 ,the dark spots 
frequently seen on the red belts usually
     occupied spaces left by sharp turns
 in the streamers1 and they were of     
the same colour as the belts1 but deeper
 in tint1 as if the fluid     medium    
could be seen to a greater depth4#ae    
,in other words1 ,jupiter is a striped  
or banded planet1 the bands lying along 
the direction of turning4 ,these bands  
are coloured in varying tints1 and the  

planet rotates very rapidly1 for the    
details in the bands pass quickly from  
one limb to the other4 ,and not only is 
the speed of rotation of the whole very 
rapid--,jupiter turns about its axis in 
a little less than ten hours1 so that a 
particle at its equator moves through   
#dff miles in each minute--but the      
various items that form the bands rotate
 in different times4 ,they may also     
alter their form and their colour4      
,jupiter seems1 then1 to be a planet    
with a great and rapidly changing       
atmosphere that extends above a         
shoreless sea formed of some liquified  
substance or substances--the whole in a 
state of flux4  ,but if we turn back to 
the ,table1 we see that ,jupiter at its 
mean distance from the ,sun is #e4b     
times that of the ,earth2 that is to    
say1 it receives only #a_/bgth of the   
light and heat that we receive4 ,but in 
,chapter ,,viii1 we learnt from ,mars   
that as this receives only #c_/gths of  
the ,earth's light and heat1 its mean   

temperature would sink to -#cj deg4,c42 
the ,earth's being #af deg4,c4 ,mars is 
therefore almost always a frozen planet2
 frozen except on its mere surface when 
this is exposed to the full rays of the 
,sun4 ,no sea there would ever be melted
 to a depth of more than a few inches1  
even at noonday in midsummer4 ,and yet  
,mars has at least ten times the        
advantages of ,jupiter4 ,jupiter1 then1 
must be a frozen planet through and     
through2 no liquid of any sort can exist
 on its surface2 no vapour of any       
substance can exist in its atmosphere4  
,it must be icebound even at its summer 
noonday4  ,yet1 from the description    
given by ,prof4 ,keeler1 it is          
manifestly not so2 and another item in  
the ,table emphasizes that it cannot be 
so4 ,the density of the ,sun is #a4d    
that of water1 ,jupiter's is #a4cc1     
showing that but a very small proportion
 7if any7 of its bulk can be solid2 the 
rest must be vaporous1 or at least      
fluid4 ,how then can we reconcile these 

inconsistencies8  ,it is in the         
dimensions of ,jupiter that we find the 
answer4 ,the mass of the planet is #cag 
times that of the ,earth2 it is indeed  
nearly three times as great as that of  
all the other planets put together4 ,but
 the aggregation of so vast an amount of
 material is of itself a source of heat2
 the chief source at the present time of
 the enormous output of heat from the   
,sun is ascribed to its gradual         
contraction2 the slow falling of its    
substance1 if we may so express it1 a   
little nearer to its centre4 ,the great 
mass of ,jupiter points to its inherent 
store of heat being much greater than   
that of any other planet4 ,and of two   
bodies equally hot1 the larger must cool
 more slowly than the smaller4 ,if1     
therefore1 all the members of the solar 
system had at one and the same moment   
possessed the same surface temperature1 
that equality would have ceased directly
 they began to radiate their heat into  
space2 the temperature of the smaller   

bodies falling more rapidly than those  
of the larger4 ,this is another example 
of the principle that has already been  
noted1 that the properties of a small   
world are not those of a large world    
divided by a constant factor4 ,it is not
 possible to conceive a model of the    
solar system in which all the           
significant factors should be true to   
the same scale4 ,if the diameters and   
distances were all made on a one-tenth  
scale1 the surfaces would be            
one-hundredth of reality1 the volumes   
one-thousandth4  ,but a radiating body  
radiates from its surface1 while the    
store of heat from which that radiation 
is kept up is supplied by its volume4   
,it follows1 therefore1 that a large and
 heavy world must differ from a small   
light world1 not merely in scale1 but   
also in kind4  ,the surface of a world  
is all that we see of it2 it is1        
therefore1 very commonly all that we    
consider4 ,but unseen1 and hence often  
unconsidered1 beneath the surface lies  

its substance or mass1 and it is this   
that determines the state and condition 
of the surface2 it is the underlying    
power4 ,two men may be contending in a  
financial struggle2 to the eye they may 
look alike1 equally prosperous2 both may
 have the same amount of money actually 
in their pockets2 but the one has       
nothing else1 the other has a great     
banking account and vast investments1   
and is1 in fact1 a millionaire2 and it  
is his unseen power and resources that  
will make themselves felt4  ,jupiter    
therefore introduces us to a new factor 
in world-condition2 not all its heat is 
derived from the ,sun2 much is inherent 
to it4 ,and though it is not possible at
 present to say that the mass of        
,jupiter being so much its inherent heat
 must be this or that quantity as a     
function of that mass1 yet in general1  
and neglecting other considerations1 we 
can say that of two worlds the one with 
the greater mass will be that with the  
higher inherent temperature4 ,this      

factor of inherent temperature was one  
that did not require to be noticed in   
dealing with the ,moon1 or ,venus1 or   
,mars1 for these and all the planets yet
 noticed are less in size1 surface1     
volume1 and mass than the ,earth1 and   
hence possess less inherent heat4 ,it is
 only now that the greater planets are  
being considered that the question of a 
source of heat1 other than the ,sun1 can
 arise4  ,but the evidence of such heat 
on ,jupiter is not to be disputed4 ,the 
albedo or reflective index of ,jupiter  
has been put by the late ,prof4 ,g4     
,bond1 of ,harvard ,college             
,observatory1 as higher than unity2 in  
other words1 that it emits more light   
than it receives4 ,this is now generally
 regarded as an excessive estimate1 but 
the albedo of the disc as a whole cannot
 be put lower than #j4gb1 or about that 
of white paper4 ,but many of the belts  
or dark regions are of a dull copper    
tint1 and the polar caps are dusky1 so  
that ,bond's estimate must be realized  

for the most brilliant zones1 as the    
brighter regions are called2 certainly  
for the whitest of the white spots4  ,no
 direct evidence of inherent luminosity 
has been obtained1 for the satellites   
disappear entirely in eclipse4 ,but     
though their shadows in transit appear  
very dark1 it is clear that they are not
 absolutely black1 since sometimes such 
a shadow is not distinguishable in      
darkness from the satellite that casts  
it2 a delicate proof that the background
 on which it falls has some intrinsic   
luminosity4  ,unless there is the       
counteracting effect of a high          
temperature1 the atmosphere of ,jupiter 
would have a pressure at the surface of 
#ajd lb4 to the square inch1 and the    
level of half pressure be attained at a 
mile and a quarter2 the reverse         
condition to that on ,mars would obtain1
 and the atmosphere of ,jupiter would be
 much denser and much shallower than    
that of the ,earth4 ,denser it probably 
is2 shallower it cannot be1 for the     

great white spots1 each often five or   
six thousand miles in diameter1 that    
range themselves at times along the     
equatorial regions till they look like  
the portholes of a ship1 evidently rise 
from depths great even as compared with 
their size4 ,but it is only by intense  
heat that the effect of the great mass  
of ,jupiter in constricting its         
atmosphere within shallow depths can be 
overcome4  ,again1 the extraordinary    
lightness of the planet1 so little above
 the density of water1 points in the    
same direction4 ,so1 not less           
unmistakably1 do the magnitude and      
rapidity of the atmospheric movements4  
,the clouds and storms of our own       
atmosphere are worked by solar heat2    
solar heat it is that draws up the      
vapours and provides the chief part of  
the energy manifested in the speed and  
strength of the air-current4 ,but solar 
heat can only give #a_/bgth the amount  
of that energy at the distance of       
,jupiter1 so that1 if they were entirely

 dependent on solar radiation1 the winds
 of ,jupiter should be very feeble4     
,further1 the difference of presentment 
due to the difference of latitude is a  
fruitful cause of inequalities of       
temperature and pressure in the         
terrestrial atmosphere4 ,but as a degree
 of latitude on ,jupiter is eleven times
 as wide as on the ,earth1 such         
inequalities connected with a given     
difference in latitude are spread over  
eleven times the distance that they     
would be on the ,earth1 and are1        
therefore1 so much the less pronounced4 
,yet1 across a gulf of #djj millions of 
miles we can clearly discern the bright 
zones of ,jupiter now narrowing down and
 constricting the red belts1 now thrust 
apart by them1 and can detect changes   
taking place in an hour of time over    
areas equal to that of a terrestrial    
hemisphere4  ,a notable peculiarity of  
,jupiter is found in the proper motions 
of its spots4 ,many of the white spots  
are exceedingly swift1 giving a rotation

 period of #i;h4 #ejm4 while the        
equatorial belt in general gives a      
period #em4 longer2 so that in #aai     
rotations 7nearly #di days7 a white spot
 will have passed entirely round the    
belt1 gaining upon it at a rate of      
nearly #bdj miles an hour4  ,the most   
famous of all the markings in ,jupiter  
is the ,great ,red ,spot1 which became  
conspicuous in #ahgh1 since when the    
spot itself1 or at least the nest in    
which it lay1 has always been visible4  
,it has been identified with a great red
 spot observed by ,hooke and ,cassini in
 #affd-f1 that appeared and vanished    
again eight times between #affe and     
#agjh4 ,it therefore has had a history  
practically as long as our telescopic   
knowledge of the planet1 and may be     
looked upon as in some sort a permanent 
feature4 ,yet that it is not in the     
nature of a portion of a solid crust is 
clear4 ,it occupies on ,jupiter much the
 position and relative area of          
,australia on the ,earth1 but whereas   

,australia of necessity rotates in one  
piece with all the other continents1 the
 ,great ,red ,spot has a rotation period
 which is neither that of the equatorial
 belt1 nor of the quickly moving white  
spots1 and is not itself stable4 ,an    
,australia on the loose is impossible1  
even unthinkable here1 but the ,great   
,red ,spot1 for all its long duration1  
is mobile and inconstant1 and is        
therefore no portion of a solid         
permanent crust4  ,the giant planet     
,jupiter1 therefore1 offers us an       
example of what we may call a semi-sun2 
a world still bubbling with tremendous  
energies of its own1 still pulsing with 
its own inherent heat1 still without a  
solid crust2 probably without a solid   
nucleus1 liquid or vaporous throughout4 
,whatever the future may hold for such  
an orb1 it is clearly no world for      
habitation at present4 ,full of colour1 
and movement1 and change as it is1 it   
lacks the ,earth's gloom of iron        
substance1 which is necessary1 no less  

than its veiling by the plant1 as a     
stage for the passion and perishing of  
mankind4  ,but if ,jupiter be a         
semi-,sun1 still a source of heat1      
perhaps even of light1 can it yield the 
means of life to its satellites8 ,for   
,jupiter is sun-like1 not merely in its 
own condition1 but also in that it is   
the centre and ruler of a system of its 
own4 ,we know already of eight          
satellites revolving round it4  ,of     
these eight1 only four--the four        
discovered by ,galileo1 in the first    
days of his possession of a             
telescope--need be considered2 the other
 four are of the same order of size as  
the asteroids1 and are indeed much      
smaller than ,ceres4  ,but the ,galilean
 satellites are of a higher rank4       
,europa1 the smallest1 is in size a twin
 to the ,moon2 ,callisto1 the outermost1
 is almost exactly the size of ,mercury2
 ,io1 the innermost1 is midway between  
the two in its dimensions4 ,but         
,ganymede1 the largest1 is almost       

comparable with ,mars1 its diameter     
being #j4de that of the ,earth instead  
of the #j4ec of ,mars4  ,but the ,moon1 
,mercury1 and ,mars have all been shown1
 on the ground of their small size1 to  
be worlds unfit for habitation2 the     
satellites of ,jupiter are1 therefore1  
all rejected on the same score4 ,nor can
 the greater nearness of their immediate
 primary compensate for their remoteness
 from the ,sun4 ,it is true that        
,jupiter presents to ,ganymede a disc   
with more than #bjj times the apparent  
area that the ,sun presents to the      
,earth1 but to make up for the          
falling-off of the solar radiation1 each
 unit of this area should radiate about 
#a_/bejth as much heat as each unit of  
the ,sun's surface4 ,in other words1 the
 absolute surface temperature of        
,jupiter should be #a_/dth that of the  
,sun1 or about #aeej deg4 ,c41 and this 
is higher than can be admitted4 ,the    
,sun and ,jupiter together cannot put   
,ganymede in as favourable a position as

 ,mars1 much less as favourable as the  
,earth4  ,the case of ,jupiter carries  
with it those of ,saturn1 ,uranus1 and  
,neptune4 ,all three1 from their high   
albedoes and low densities1 are still in
 a vaporous condition2 still in some    
sort1 semi-,suns2 sources of a certain  
amount of heat1 and not recipients      
merely4 ,the days are yet far distant   
when a solid crust can form on any one  
of them1 and the water condense from the
 steamy atmosphere to form oceans1 seas1
 and rivers4 ,not till then1 if at all1 
when water as a liquid1 water that      
flows1 is present1 can life begin to    
appear and enter on its long course of  
change4     ,,chapter ,,xi  ,,when ,,the
 ,,major ,,planets ,,cool   ,the        
question has been asked3 ,it is evident 
that life cannot exist at the present   
time on the outer planets1 since they   
are in a highly heated and quasi-solar  
condition2 but when they cool down1 as  
cool they must1 and a solid crust is    
formed1 may not a time come when they   

will be habitable8 ,it seems impossible 
to think that worlds so beautiful to our
 eyes and so vast in scale are destined 
never to be peopled by intelligent      
beings4  ,it is clearly difficult to    
answer satisfactorily a question that   
requires so deep a plunge into the      
recesses of the unknown future2 yet1 so 
far as our knowledge goes1 there is no  
reason to think that ,jupiter will be   
more habitable then than it is now4 ,the
 difficulty of the small supply of light
 and heat received from the ,sun would  
apparently still remain1 if indeed1 the 
cooling of the ,sun itself would not    
increase it4 ,we do not know of any     
means by which our ,sun could so        
increase its radiation as to supply to  
,jupiter from #be to #cj times as much  
heat as it now receives1 and this would 
be necessary to place it in the same    
favoured condition as the ,earth4 ,if so
 great a change were to take place in   
the ,sun1 life would be scorched out of 
existence on all planets nearer than    

,jupiter1 and1 similarly1 if the solar  
emission were increased to meet the     
necessities of ,uranus or ,neptune1 even
 ,jupiter would fall a victim4  ,but we 
may consider it as a conceivable case   
that a planet of the exact dimensions of
 ,jupiter may be revolving in an annual 
period of the same length as his1 round 
some star that is capable of affording  
it adequate nourishment2 and so with the
 three other giant planets4 ,the actual 
,jupiter and ,saturn of the solar system
 have1 so far as we can tell1 neither   
present nor future as habitable worlds1 
but we can consider what would be the   
case of imaginary bodies of similar     
dimensions in systems where the supply  
of heat would be sufficient4 ,or we can 
neglect the question of temperature     
altogether1 as we did at first in the   
case of ,mars4  ,all the four planets   
must shrink much in volume before their 
solidification will take place4 ,their  
average density at present but little   
exceeds that of water2 indeed1 ,saturn  

is not so dense as water2 yet we must   
suppose that the same elements are in   
general common to the ,earth and to them
 all4 ,if we assume1 then1 that the four
 planets all cool to the point of       
solidification1 their densities must be 
much increased1 and their volumes       
correspondingly diminished4 ,since all  
four greatly exceed the ,earth in mass1 
it is but natural to expect that1 when  
they have assumed the terrestrial       
condition1 they will be more closely    
compacted than the ,earth1 and their    
densities in consequence will be        
greater4 ,it will1 however1 be simpler  
if we assume exactly the same density   
for them as for the ,earth4 ,jupiter    
will then have shrunk to about          
one-fourth of its present volume1 and   
the statistics for the four planets will
 run as in the following ,table3        
,,statistics ,,of ,,the ,,four ,,outer  
,,planets ,,if ,,with ,,the ,,same      
,,density ,,as ,,the ,,earth            
,,proportions ,,of ,,the ,,planets3--   

,uranus  ,neptune  ,saturn  ,jupiter    
,diameter in miles                      
#aicjj    #bjdjj    #cfjjj   #edjjj     
do                ,symbol  #a    #b4dd  
#b4eg     #d4ef    #f4hb     ,surface1  
,symbol  #a    #f4j      #f4f     #bj4h 
#df4f     ,mass and ,volume1    ,symbol 
#a   #ad4f     #ag4j     #id4h   #cag4g 
,gravity at surface1 ,symbol  #a        
#b4dd     #b4eg     #d4ef    #f4hb      
,rate of ,fall1 ,feet in     the ,first 
,second                   #ci4b         
#da4c     #gc4c   #aji4g                
,,atmosphere1 assuming the   total mass 
of the atmosphere   to be proportional  
to   the mass of the planet3--          
,pressure at the surface in lb4     per 
square inch                    #hh4b    
#ig4j    #cje4h   #fhe4j   ,pressure at 
the surface in     atmospheres          
#f4j      #f4f     #bj4h    #df4f       
,level of half-pressure in miles        
#a4cg     #a4cj     #j4gc    #j4di      
,boiling point of water at     surface  
#abg deg4,c    #abi deg4,c    #adh      

deg4,c   #afd deg4,c  ,jupiter offers   
two peculiarities4 ,in its shrunken     
condition1 its diameter1 instead of     
being eleven times that of the ,earth1  
will be not quite seven1 and the force  
of gravity at the surface will be       
greater than that of the ,earth in the  
same proportion4 ,a man who here weighs 
#aej lb4 will there weigh over #ajjj    
lb42 and the muscular effort of movement
 will be increased in the same ratio4   
,the athlete who here can clear a height
 #e ft4 #h in4 will there1 with like    
pains1 surmount #aj inches2 and other   
efforts will be in the same proportion4 
,the atmosphere1 supposing it to be in  
proportion to the mass of ,jupiter1 will
 exercise a pressure of #df-a_/b        
atmospheres1 or more than #fhj lb41 to  
the square inch4 ,following on this     
enormous pressure at the surface would  
be the rapidity with which the          
atmosphere would thin out in the upward 
direction4 ,the level of half-pressure  
would be attained by ascending less than

 half a mile in height2 that is to say1 
there would be a difference of pressure 
of #cdj lb4 on the square inch from that
 experienced at the sea-level4 ,we know 
from the fact that fishes live at       
enormous depths in the ocean1 that      
living organisms can be constructed to  
endure great pressures1 but they are not
 constructed to endure great alterations
 of pressure4 ,the deep-sea fishes are  
as instantly killed by being brought up 
to the surface1 as the surface fishes or
 the land animals would be if they were 
plunged into the depths4 ,and it is     
clear that on ,jupiter a low range of   
hills that on the ,earth would be       
considered only an easy climb1 would be 
an impassable barrier1 not only from the
 immense exertion of mounting it1 but   
chiefly from the unendurable change of  
pressure which the ascent would involve4
  ,the sevenfold gravity of ,jupiter1   
taken in connection with this enormous  
atmospheric pressure1 would tend to make
 the meteorological disturbances of the 

planet violent far beyond anything of   
which the ,earth can furnish an example4
 ,the atmosphere would possess a high   
viscosity1 and differences in condition1
 pressure and saturation would tend to  
accumulate1 until at length the balance 
would be restored with explosive        
suddenness and force4 ,here our most    
violent tornadoes may reach a speed of  
#ajj miles an hour2 on ,jupiter1 gales  
of five or six times that velocity would
 be common4 ,we cannot conceive that    
living organisms would be able to grow1 
flourish and multiply where the         
conditions were so cataclysmic4  ,this  
difficulty must always exist where the  
planet is great in mass1 and the force  
of gravity high at the surface4 ,the    
case of ,saturn is not so extreme as    
that of ,jupiter1 though it is probably 
sufficiently severe to exclude it from  
the ranks of worlds that could ever be  
dwelt in4 ,the atmospheric pressure     
would be about #ba atmospheres1 or more 
than #cjj lb4 on the square inch4 ,the  

level of half-pressure would be reached 
at about three-quarters of a mile1 and  
the force of gravity be nearly #d-a_/b  
times that of the ,earth4  ,but the     
serious condition for ,saturn would come
 from that feature which renders it by  
far the most attractive of all the      
planets seen in the telescope1 the      
presence of the wonderful ,ring system4 
,to us1 viewing ,saturn from afar1 and  
from practically the same direction as  
the ,sun1 the ,rings are seen lit up2   
but to a dweller on ,saturn1 the ,rings 
during the day are between his world and
 the ,sun1 and hence turn their dark    
side toward him4 ,more than that1 the   
telescope shows us that the ,rings cast 
a shadow on the planet2 in other words1 
they eclipse part of it2 and this shadow
 changes its position with the progress 
of the ,saturnian year4 ,proctor        
computed that if the ,rings were a      
hundred miles in thickness1 the equator 
would suffer1 in consequence1 total     
eclipse for nearly ten days at each     

equinox1 and partial eclipse for about  
forty days more4 ,moving away from the  
equator1 each higher latitude would have
 a longer and longer period of eclipse  
in the winter half of its year2 the     
higher the latitude1 the later after the
 autumnal equinox the eclipse would     
begin1 and the longer it would last1    
until about latitude #dj deg4 was       
reached4 ,here the eclipses would begin 
nearly three terrestrial years after the
 time of the autumnal equinox4 ,at first
 the ,sun would be eclipsed only in the 
morning and evening of each day1 but the
 length of the daily eclipse would      
increase1 until the ,sun was hidden the 
whole day long4 ,this period of total   
eclipse would last for about #f years #h
 months1 terrestrial reckoning1 or with 
the periods of partial eclipse1 #h years
 and nearly #aj months4 ,whatever the   
efficiency of the ,sun that afforded    
light and heat to such a planet1 it is  
clear that such eclipses must be fatal  
to life in two ways3 light and heat     

would be cut off from wide regions of   
the planet for long periods of time1 and
 terrible meteorological convulsions    
must follow in the train4 ,here on the  
,earth1 though a total eclipse generally
 lasts only two or three minutes1 the   
atmospheric disturbance is perceptible1 
and the fall of temperature very marked1
 and it does not require much reflection
 to see that the analogous disturbance  
in an atmosphere twenty times as dense  
must be terrific indeed during an       
eclipse that lasts not a few minutes    
only1 but for more than six of our      
years4  ,the case of ,uranus introduces 
us to another class of conditions fatal 
to habitability4 ,the equator of        
,jupiter is inclined only #c deg4 to the
 plane of its orbit2 the difference in  
its seasons is1 therefore1 almost       
imperceptible2 there is hardly any      
alteration in the incidence of the solar
 rays2 it is1 as if on the ,earth1 the  
height of the ,sun at noon in mid-winter
 were what it actually is on the #adth  

of ,march1 and its height at midsummer  
the same as we observe on ,march #bh4   
,the inclination of the equator of      
,saturn is considerably greater than    
that of ,mars or the ,earth1 so that its
 seasons are more pronounced1 but not to
 an extent that would introduce any     
radical difference4 ,but for ,uranus1   
the inclination of the equator to the   
plane of the orbit is #hb deg4 ,if this 
were the case for the ,earth1 the       
noonday sun for ,london would be1 at the
 spring equinox1 #ch-a_/b deg4 high as  
at present1 but its altitude day by day 
would increase with great rapidity1 and 
before the end of ,april1 the ,sun at   
noon would be right in the zenith1 and  
#ac deg4 above the horizon at midnight4 
,at midsummer1 indeed1 it would be only 
#ei deg4 high at noonday1 but it would  
be north of the zenith instead of south1
 and at technical midnight1 it would    
still be #dd deg4 in altitude1 thus     
moving round in a very small circle1    
only #ae deg4 in diameter4 ,from about  

,april #ah to ,august #be--that is to   
say1 for #abi days--the ,sun would never
 set1 and unlike the summer day of our  
own polar regions now1 wherein the ,sun1
 though always present1 is always low   
down in the sky1 for much of that period
 it would pass the meridian quite close 
to the zenith4  ,as the year of ,uranus 
is #hd times the length of our year1 the
 ,london of ,uranus would have to endure
 not far short of #cj years continuous  
scorching4  ,and the winter would be as 
long2 the perpetual day of summer would 
be replaced by a night as enduring4     
,more than #bi years of unbroken        
darkness1 of unmitigated cold1 cannot   
possibly ever consist with the          
conditions necessary for life upon a    
planet4 ,whatever the brightness of the 
imagined sun of ,uranus1 if for #bi     
years at a time that sun were below the 
horizon1 the water on the planet must be
 congealed1 and during the #bi years of 
unbroken day all the water would be as  
certainly evaporated4  ,thus1 though    

,uranus is not burdened by the enormous 
mass of ,jupiter1 nor overshadowed1 like
 ,saturn1 by a system of rings1 the     
extraordinary inclination of its axis   
introduces a condition which is as fatal
 to it1 as a world to dwell in1 as any  
of the disabilities of the other        
planets4  ,it is curious that these four
 outer planets1 that resemble each other
 so strikingly in many of their         
conditions--in their vast size1 high    
albedo1 low density1 and vaporous       
envelopes1 that show1 in their spectra1 
not merely the lines of reflected       
sunlight1 but also special lines due to 
their own atmospheres 7the chief of     
these being common to all the four      
planets7--should yet1 in the inclination
 of their axes to the plane of their    
orbits1 display every possible variety4 
,the axis of ,jupiter is almost normal  
to its orbit1 that of ,uranus lies      
almost in the plane of its orbit4 ,the  
axes of ,saturn and ,neptune have a mean
 inclination1 but it would appear that  

the rotation of ,neptune is in the      
reverse direction to that of planets in 
general1 so that the true inclination is
 usually taken as being the complement  
of the observed angle1 as if the axis   
were turned right over4 ,it is uncertain
 whether this would have any important  
effect upon the habitability of the     
planet1 but it supplies the fourth      
possible case for the position of the   
axis4     ,,chapter ,,xii  ,,the ,,final
 ,,question   ,in passing in review the 
various members of the solar system1 it 
has been seen that there are many       
conditions that have to be fulfilled    
before a planet can be regarded as the  
possible abode of life1 because there   
are many conditions necessary in order  
that water may exist on its surface in  
the liquid state4 ,the size and mass of 
the planet are restricted within quite  
narrow limits2 and a world much larger  
or much smaller than our own is         
necessarily excluded4 ,the supply of    
light and heat received from the ,sun   

must not fall much below that received  
by the ,earth1 nor greatly exceed it2 in
 other words1 the distance of the planet
 from its ,sun is somewhat precisely    
fixed1 since the light and heat vary    
inversely not as the distance1 but as   
its square4 ,of course1 in different    
systems1 with suns of different power1  
the most favourable distance will not be
 the same in each2 but in any system    
there will be one most advantageous     
distance1 and no great departure from it
 will be possible4 ,this condition      
further implies that the planetary      
orbits must be nearly circular2         
pronounced eccentricity1 such as the    
orbits of even our short-period comets  
display1 would be fatal to the          
persistence of water in the liquid      
state1 and hence to the continuance of  
life4 ,a wide discordance between the   
planes of the planet's equator and of   
its orbit1 by rendering the seasons     
extravagantly diverse1 would act as     
prejudicially as an eccentric orbit1 and

 a rotation period equal to that of     
revolution would mean that one          
hemisphere was eternally frozen while   
the other was exposed to perpetual heat4
  ,it follows that in any given system  
there can be at most only one or two    
planets upon which life can find a home1
 and this only where the right          
conditions of size and mass1 of rotation
 period1 inclination of axis1 and shape 
of orbit1 all co-exist in a globe at the
 proper distance4 ,but the type of      
system offered by our ,sun and his      
planets is not the only one that exists4
 ,a very large proportion of stars are  
binaries--two suns revolve round their  
common centre of gravity4 ,in many cases
 the two suns are separable in the      
telescope1 and their relative movements 
can be measured2 in other cases1 termed 
spectroscopic binaries1 we only learn   
that a star which appears absolutely    
single has two components from the      
evidence of its spectrum2 the           
spectroscope revealing two sets of lines

 that vibrate to and fro with respect to
 each other4 ,yet1 again1 a third class 
of double stars has made itself known in
 the ,algol variables4 ,the optical     
double stars are cases where the two    
components are far distant from each    
other1 and hence can be distinguished in
 our telescopes as separate points of   
light4 ,the spectroscopic binaries are  
cases where the two components are too  
close to be separately perceived1 but   
where the two are not greatly unequal in
 brightness1 so that the spectrum of the
 one does not overpower that of the     
other4 ,the ,algol variables are cases  
where the two components are of very    
unequal brightness1 and1 being very     
close to each other1 are so placed with 
respect to the ,earth that the fainter  
partly eclipses the brighter in its     
revolution round it1 and so causes a    
temporary diminution in its light at    
regular intervals4 ,all these three     
classes of binary systems are now known 
to be very numerous4 ,prof4 ,campbell   

estimates that fully one star in six is 
a spectroscopic binary4 ,but there must 
be many binary systems that do not      
reveal themselves--double stars where   
the companion is too faint or too close 
to be detected1 ,algol systems where the
 companion does not pass before its     
primary--and it seems almost certain    
that simple systems1 like that of which 
our ,sun is the unchallenged autocrat1  
must be comparatively rare4  ,but the   
problem of the movements of a planet    
attendant upon two or more suns is one  
of amazing complexity1 and our greatest 
mathematicians have as yet only been    
able to deal with the approximate       
solution of a few very special cases4   
,these are1 however1 sufficient to show 
that the orbit of a planet so placed    
would be most irregular2 the variations 
in the supplies of light and heat       
received would be as great as even      
comets experience within the solar      
system1 and1 what would be more         
disastrous still1 these variations would

 not be periodic but irregular4 ,one    
year would be unlike that which preceded
 it1 and would be followed by changed   
conditions in the next4 ,plants and     
animals would never have the chance of  
acclimatizing themselves to these       
ever-changing vicissitudes4 ,the        
stability of condition essential for the
 maintenance of water in a liquid state 
would be wanting2 and1 in consequence1  
,life could neither come into existence1
 nor persist if it once appeared4  ,so  
far1 therefore1 our line of thought has 
led us to recognize that ,life can exist
 in comparatively few of the innumerable
 stellar systems strewn through infinite
 space1 and in any given system it can  
at best find only one or two homes4 ,the
 conditions for a ,life-bearing planet  
are thus both numerous and              
stringent--there is no elasticity about 
them4 ,it is not sufficient that a      
planet might fulfil many or even most of
 these conditions2 failure in one is    
failure altogether2 one black ball      

excludes2 the candidate who fails in a  
single subject is ploughed without      
mercy4 ,and in most cases the failure is
 final2 no opportunity is given to the  
candidate to sit again4  ,but ,space is 
not the only horizon along which our    
thought must be directed2 there is also 
the horizon of ,time4 ,every world must 
have its ,past and its ,future1 as well 
as its ,present4 ,for some worlds the   
conditions are so fixed that1 like      
,jupiter and ,saturn1 they are not now  
worlds that can be dwelt in1 they never 
were in that condition1 and they never  
can be2 their enormous mass forbids it4 
,mercury and the ,moon at the other end 
of the planetary scale are also         
permanently disabled2 their             
insignificant size excludes them4 ,there
 was also a time when the ,earth was not
 a world of habitation2 it was without  
form and void2 hot and vaporous1 even as
 the four outer planets are now4 ,now it
 is inhabited1 but there may come a time
 when this phase of its history has run 

its course1 and either from a falling   
off in the tribute of light and heat    
rendered to it by the ,sun1 or from the 
gradual desiccation of the surface1 or1 
perchance1 from the slow loss of its    
atmosphere1 it may approach the         
condition of ,mars1 and in its turn be  
no longer an abode of life4 ,many       
planets are essentially debarred from   
ever entering on the vital stage2 but of
 those to which such a stage is         
possible1 it can only form an incident  
in the entire duration of the orb4 ,and 
if our ,earth is any type or example of 
the vital stage in general1 vast aeons  
must run their course from the first    
appearance of the humblest germs of life
 up to the bringing forth of ,life in   
conscious ,intelligence4 ,one hundred   
million years are freely spoken of in   
this connection by those who study the  
crust of the ,earth and those who are   
occupied with the relations of the      
varied forms of life4 ,man is the latest
 arrival on this planet1 and however far

 back we try to push the time of his    
earliest appearance1 it is beyond       
question that that time1 relatively to  
the entire duration of the ,earth since 
a solid crust began to form1 is but as  
yesterday4 ,if1 from some other globe in
 the depths of space1 this world of ours
 could have been watched during the long
 aeons that elapsed from its first      
separation from the solar nebula down to
 the time when it first possessed a     
surface of land and water1 and from that
 time1 again1 throughout the            
hypothetical one hundred million years  
that preceded the advent of man1 then1  
during all those aeons1 those imagined  
observers would have had under their    
scrutiny a world as yet without         
inhabitant4 ,the ,earth now is in the   
inhabited condition1 but science gives  
us no clue as to how long that condition
 will endure2 rather such hints as are  
afforded us would seem to point to its  
lasting but for a brief season as       
compared with the indefinite duration   

which preceded it1 and the indefinite   
duration which shall follow4  ,if this  
thought be sound1 it places before us an
 entirely new and most serious          
consideration4 ,the world predestined   
for habitation must not only have its   
size within certain narrow limits1 its  
distance from its central sun in a      
certain narrow zone1 its rotation       
period1 the inclination of its axis1 the
 eccentricity of its orbit1 all suitable
 alike1 but even if in these and in all 
other necessaries it is perfectly       
adapted for habitation1 yet it will be  
only during a relatively small fraction 
of its entire duration that ,intelligent
 ,life1 clothed in material form1 will  
find a place upon it4  ,let us sum      
shortly what we know and what we        
conclude4 ,we know that this1 our       
,earth1 is a habitable globe1 for we    
ourselves are living upon it4 ,we know  
what constitutes the physical basis of  
our life1 and under what conditions on  
this ,earth it flourishes1 and under    

what conditions it is destroyed4 ,if we 
turn our eyes from this1 our ,earth1 and
 look out upon the starry skies1 we see 
the other planets of our system1 and the
 suns which are the centres of other    
systems4 ,from the consideration of the 
planets in our own system1 we have seen 
how stringent and how many are the      
conditions imposed for ,life to be      
possible4 ,round our ,sun there is but a
 narrow zone in which a habitable world 
may circle2 in this zone there is room  
for but few worlds1 and we actually know
 of three alone1 the ,earth1 the ,moon1 
and ,venus4 ,we know that the ,earth can
 be and is inhabited2 that the ,moon is 
not and cannot be inhabited2 and that   
,venus1 though of habitable size1 may   
yet be subject to the fatal             
disqualification of always turning the  
same face to the ,sun4 ,of other        
planetary systems than our own1 we      
actually know of none1 but we assume    
that there are such1 and as numerous as 
there are suns in the starry depths4    

,but of these planetary systems we can  
rule out1 as containing no habitable    
member1 all such as circle round double 
or multiple suns or1 indeed1 round any  
single star that1 from whatever cause1  
is largely variable and1 therefore1 much
 less stable than our own4 ,mira ,ceti1 
which in #e months increases its        
brightness #ajjj times1 may stand as an 
example4 ,probably these                
disqualifications rule out of court the 
great proportion of the stellar systems4
 ,of the few1 comparatively speaking1   
single and stable suns that remain in   
the heavenly abyss1 we must conclude1   
from what we know of our solar system1  
that they1 too1 have but a narrow zone1 
outside of which no world would be fit  
to dwell in2 whilst in the zone the few 
worlds which might exist must violate no
 one of many strict conditions4 ,if we  
assume that there are a hundred million 
stars within the ken of our telescopes1 
we may well believe that not more than  
one in a hundred of these would fulfil  

the condition of being a single and     
stable sun1 such as ours4 ,of the       
planets revolving round these million   
suns--stable and efficient suns--can we 
expect that in more cases than one in a 
hundred there will be a planet in the   
habitable zone fulfilling all the other 
conditions of habitability1 of size1    
mass1 inclination of axis1 circular     
orbit1 and rotation8 ,of these ten      
thousand earths which may be made fit   
for the habitation of ,man1 can we      
assume that even one in a hundred is now
 at that epoch in its history when it is
 no longer without form and void1 when a
 division has been made between the     
waters under the firmament and those    
that are above the firmament2 when the  
waters under the heaven have been       
gathered into one place1 and the dry    
land has appeared1 and when the earth   
and the waters have brought forth life  
abundantly8 ,out of a hundred million of
 planetary systems throughout the depths
 of space1 can we suppose that there are

 even one hundred worlds that are       
actually inhabited at the present       
moment8 ,these numbers and proportions  
certainly are not1 and cannot be1 based 
on knowledge2 they are given as         
illustrations only2 but1 vague as they  
are1 they suggest that our ,earth may be
 neither one of many inhabited earths1  
nor yet unique1 but one of a few--indeed
 of a very few4  ,and then the objection
 is raised3 ,if our own ,earth is but   
one of1 perhaps1 two inhabited worlds in
 the solar system2 and of perhaps one or
 two hundred inhabited worlds throughout
 the furthest space that we can scan2   
why is all this waste8 ,of all the      
countless millions of stellar systems   
without living organisms as inhabitants1
 we cannot tell the purpose for the     
simple reason that we do not know it2   
but of waste in the solar system1 there 
is no question4 ,relatively speaking1   
this is quite insignificant1 for we     
cannot consider that as waste material  
which is useful and1 indeed1 essential  

to existence4 ,for1 consider first the  
material in the ,earth itself4 ,its     
total volume is #bfj1fac1jjj1jjj cubic  
miles1 but man only lives upon its      
surface of less than #bjj million square
 miles in extent1 and he can not probe  
down as far as ten miles below it1      
through the depths of ocean or by his   
deepest mine4 ,thus we are left with    
over #beh thousand million of cubic     
miles that man1 or plant1 or beast can  
never make direct use of4 ,but without  
this #beh thousand million cubic miles  
that he can never sow nor reap1 the     
overlying platform on which he dwells   
would be useless for retaining the air  
or the water by which he lives4 ,no less
 essential is the ,sun2 its vast bulk of
                                        
#b1jjj1jjj1jjj1jjj1jjj1jjj1jjj1jjj1jjj  
tons  can1 in no single unit1 be counted
 waste1 for it is from this that the    
heat and light necessary for life on the
 ,earth is derived4 ,but the tonnage of 
all the planets combined is but #j4ac   

per cent of the ,sun alone2 and a       
wastage1 if such it is1 like this is    
insignificant from a material point of  
view4  ,there is a type of politician at
 the present day who is convinced that  
the highest purpose to which land can be
 put is to build upon it2 that being1 in
 general1 the use giving the highest    
money return per square foot1 though the
 return does not always fall to the     
builder4 ,it has taken not a little     
agitation and popular pressure to       
enforce the truth that cultivated land  
is also of use4 ,but there are few who  
realize that land that is neither built 
upon nor cultivated is also essential4  
,our barren moors and bleak hillsides1  
wastelands as we call them1 are         
absolutely necessary as collectors of   
the water by which we live4 ,from them  
our springs take their source2 and they 
supply our cities with the first        
necessity of life4  ,we find1 then1 in  
this universe so far as we can know it1 
that ,space is lavishly provided1       

,matter is lavishly scattered1 ,time is 
unsparingly drawn upon1 but ,life in any
 form1 and especially in its highest    
form1 is1 relatively speaking1 very     
sparsely given4 ,that very circumstance 
surely points to the overwhelming       
importance of conscious1 intelligent    
,life1 and the insignificance of        
lifeless matter in comparison with it4  
,we have to exhaust arithmetic in       
computing the size1 the mass1 the output
 of heat and light of our ,sun1 yet it  
is but the hearth-fire and lamp of      
terrestrial life2 and its amazing       
agglomeration of matter and energy is   
ungrudgingly devoted to this humble     
purpose4 ,whatever view we hold as to   
the scheme of the universe2 whether with
 the unthinking we fail to recognize    
,thought and ,purpose behind its        
marvellous manifestations1 or1 with the 
thoughtful1 realize that only ,infinite 
,thought could provide so wonderfully   
for the bringing forth of thought in    
living material organisms1 the          

conclusion still remains3 living        
intelligences are1 by the direct        
testimony of the universe itself1 its   
noblest and most precious product4  ,the
 plea is often made that as we find life
 adapting itself to a great variety of  
conditions on this ,earth1 we must not  
set limits to its power of adaption to  
the conditions of other worlds4 ,but    
this plea is an unthinking one4 ,the    
range of conditions through which we    
find life on this ,earth is as nothing  
to the range given by the varied sizes  
and positions of the different planets2 
and even on our ,earth1 life in the     
unfavoured regions--the tops of         
mountains1 the polar snows1 the         
waterless deserts1 the ocean depths--is 
only possible because there are more    
favoured regions close at hand1 and     
there are1 as it were1 crumbs that fall 
from the rich man's table4 ,a well-known
 litterateur in setting forth a hundred 
ways of making money gave great         
prominence to the method of living as   

caretaker in an empty house4 ,but       
residing in an empty house does not1 in 
itself1 supply the means of sustenance2 
these have to be furnished by the       
wealthier man who employs the caretaker4
  ,another plea for vague sentiment in  
this matter is that we cannot expect    
that intelligent beings on other worlds 
would have the same form as man1 and if 
not the same form1 then1 that the same  
conditions of existence would not hold  
good for them as for us4 ,both          
contentions are unsound4 ,protoplasm is 
the physical basis of all the life that 
we know1 whatever its form2 though these
 forms are to be counted by the million1
 and are as diverse as they are         
numerous4 ,and everywhere and always1   
water is found essential to protoplasmic
 life4 ,of life of any other kind we do 
not know any examples2 we have no       
instance2 if such exist1 then they are  
beyond our ken4  ,and neither           
anthropologist nor biologist would admit
 that the form of intelligent life was  

an unrelated accident4 ,whether the form
 brought the intelligence1 or the       
intelligence the form1 or both were     
evolved together1 the one reacting on   
the other1 the human form and the human 
intelligence are associated1 and we feel
 this to be so of necessity4 ,in #ahia1 
,dr4 ,eugene ,dubois found in ,java a   
molar tooth and a portion of a skull1   
and later the thigh bone of the left    
leg1 and two more teeth4 ,such as they  
were1 these relics appeared nearer in   
form to the corresponding fragments of  
an average ,australian than to those of 
an ape1 and on this ground intelligence 
was claimed for the creature of which   
they were the remains1 and it was given 
the name of ,pithecanthropus1 or        
,ape-,man4 ,the discovery aroused much  
discussion1 but on all sides it was     
unhesitatingly assumed that the         
difference between the form of          
,pithecanthropus and that of the most   
similar ape was an index of its superior
 intelligence over the ape1 just in so  

far as that difference was in the       
direction of the modern human form4 ,the
 same remark applies to the recent      
discovery of very ancient human remains 
in ,sussex4 ,never at any time has it   
been supposed that the physical frame   
has followed any other path in the      
evolution of intelligence than that     
which brought forth man4 ,the           
flesh-eating animals have attained      
efficiency in hunting and warfare by    
variation along many types of form2 the 
herbivora have been not less varied in  
the forms by which as races they secured
 themselves from destruction2 but       
,thought has been associated with the   
development of one type or form only1   
and the entire future of ,thought on    
this planet rested neither with mammoth 
nor cave-bear1 but with the possessor of
 the erect stature1 the upward look1 the
 differentiation of hand and foot1 even 
in their crudest and earliest stages4   
,swift1 in ,gulliver's ,travels1        
conceived of a land where the           

intelligence and conscience of ,man     
dwelt in the form of the horse1 and the 
human form tabernacled the instincts of 
the beast4 ,h4 ,g4 ,wells1 in his ,war  
of the ,worlds1 attributed intelligence 
to monsters--half-cuttlefish and        
half-anemone1--and the human form to    
their helpless1 unresisting prey4 ,both 
conceptions are as scientifically absurd
 as they are gross and revolting2 and if
 it were possible for the skeleton of   
creatures from other worlds to be       
brought to us here1 then biologists     
would as confidently pronounce on their 
intelligence as they do on the extinct  
forms of bygone ages--the nearer to the 
human form1 the nearer to the human     
mind4 ,we have found the figures of     
reindeer1 horse1 and mammoth scratched  
in outline on a mammoth tusk2 but though
 the artist has left no other trace1 we 
need no further evidence of his bodily  
form4 ,neither horse1 nor reindeer1 nor 
mammoth made those rough outlines2 they 
were drawn by a man4 ,more striking     

still1 ,france yields us chipped flints 
by the million1 flints so slightly      
shaped that it is in dispute whether    
they may not have been so broken by the 
action of torrents4 ,but there are only 
two theories about them2 either they    
were so chipped by natural action1 or   
they were designedly so chipped by      
creatures resembling ourselves in head  
and hand4  ,the question that has been  
dealt with in this volume is a          
scientific one1 and the attempt has been
 made to treat it as such1 and to argue 
from known physical facts as to the     
conditions of worlds which we cannot    
visit4 ,but by many the question is     
generally discussed wholly apart from   
physical facts at all1 and it becomes   
one of sentiment and of religious       
sympathy4 ,yet1 curiously enough1 the   
division between those who think that   
all worlds must be inhabited and those  
who think that our own world stands     
alone is not coincident with any line of
 theological divisions1 but rather cuts 

across all such4 ,some believers in     
,christianity argue that since ,god has 
filled this world with ,life1 ,life has 
been ,his purpose in the world1 and must
 therefore have been ,his purpose in all
 other worlds--they too must be filled  
with ,life in like manner4 ,other       
believers argue that this world was the 
scene of the ,incarnation of ,our ,lord1
 and is therefore unique in that        
respect2 and that this uniqueness sets  
its stamp upon this world in all        
respects4 ,opponents to ,christianity   
are divided into the same two classes1  
the one arguing that wherever there is  
matter the inevitable course of         
evolution will produce life1 and        
eventually intelligent life4 ,the other 
class are equally clear that all forms  
of life are special1 the result of the  
particular environment1 and that it is  
unreasonable to expect that any other   
world has had the same history as our   
own1 or that the same special conditions
 have prevailed elsewhere4 ,in other    

words the belief that there are other   
inhabited worlds has depended chiefly   
neither on science nor on religious     
belief1 but upon sentiment4 ,there are  
some who like to think themselves1 and  
the race to which they belong1          
altogether exceptional2 others delight  
in finding themselves reflected wherever
 they look4 ,so far as ,science has     
progressed and can return an answer to  
an enquiry that exceeds so far the      
bounds of our direct observation1 it    
dissents from both orders of thought4   
,the conditions of life are indeed      
narrow1 special1 restricted2            
intelligent1 organic life must1         
relatively speaking1 be a rarity in the 
universe1 but we lack the information   
that would enable us to affirm with any 
confidence that such life is only to be 
found upon this world of ours4 ,heavy as
 the odds are against any particular    
world being an inhabited one1 yet when  
the limitless extent of space is        
considered1 and the innumerable numbers 

of stars and systems of stars1 it seems 
but reasonable to conclude that though  
inhabited worlds are relatively rare1   
the absolute number of them may be      
considerable2 considerable1 if not at   
one particular moment of time1 yet when 
the whole duration of the universe is   
admitted4  ,but there is a religious    
question connected with this enquiry2   
one that goes down to the very roots of 
man's deepest thoughts and aspirations4 
,as individuals our days on the ,earth  
are as a shadow1 and there is none      
abiding2 as individuals we pass and     
disappear2 and though the race remains1 
yet as far as science can guide us and  
enable us to penetrate the future1 the  
same lot awaits the race as well4       
,slowly but surely the water of a planet
 will combine with its substance or     
disappear into its crust4 ,the cooling  
of the ,sun1 though it may be long      
delayed1 would seem to be inevitable in 
the sequel4    ,oh1 life as futile then 
as frail4        99       99       99   

99    ,what hope of answer or redress8  
,behind the veil1 behind the veil4  ,it 
is to this veil that we are now brought4
 ,it seems impossible to believe that   
,life1 so rare a fruit of the universe1 
intelligent ,life1 conscious ,life1 to  
which the long course of evolution has  
been so manifestly leading up all       
through the long ages1 should have no   
better destiny than a final and hopeless
 extinction2 that this ,earth and all   
the efforts and aspirations of the long 
generations of men should have no       
worthier end than to swing1 throughout  
the eternal ages1 an empty1 frozen heap 
of dust1 circling round the extinct     
cinder that was once its ,sun4 ,if we   
look backward1 we seem to discern clear 
signs of progress2 if we look forward1  
we discern nothing but the veil4        
,science is but organized experience1   
and experience of the future we have    
none4  ,there was a time when on this   
world there was no life2 a time when    
life began4 ,how did it begin8 ,under   

what conditions8  ,of that great        
change--when non-living matter first    
became endowed with life1 became so     
endowed not by the action and           
intervention of other living matter1 but
 without it--we have no knowledge1 no   
experience4 ,and so long as this        
continues to be the case1 that change1  
the greatest physical change that has   
yet taken place in the history of the   
universe1 the first change of the       
non-living into the living1 is outside  
the reach of science2 it lies beyond its
 border4 ,we may guess and speculate    
about it1 but speculation is not        
science2 we may spin words about it with
 the utmost skill of the dialectician1  
but metaphysics is not science2 it can  
never come within the scope of science  
until it has first come within the scope
 of experience4  ,there is1 therefore1 a
 veil behind us as well as the one that 
encloses us in front2 and as hitherto   
,science has failed to pierce the veil  
of the past1 it is even less able to    

pierce the veil of the future2 for of   
the future we have no experience4       
99       99       99       99       99  
,here1 then1 our enquiry must end1 for  
it is an enquiry of physical science2   
the search for living material organisms
 endowed with intelligence4 ,how life   
first came upon this ,earth1 or when1 or
 where1 is beyond the power of science  
to determine4 ,yet it did come4 ,there  
was a time when there was no life here2 
none1 not even the humblest form of it2 
nor was there any hint or foreshadowing 
of it1 still less of all its infinities 
of form1 and possibilities of           
development4  ,once ,life was not1 yet  
,life came1 and now1 life is abundant1  
but abundant only in worlds quite       
exceptional in their conditions1 and    
therefore few in number2 it is even     
conceivable that this ,earth of ours may
 be unique4 ,but life as we know it1    
protoplasmic life1 life dependent upon  
water1 the life of intelligence united  
to the material organism1 is under      

sentence of death4 ,has it any future   
beyond that veil8 ,is there any kind of 
life not subject to these narrow        
limitations2 not under the inexorable   
decree8  ,to questions such as these    
,science has no reply to give2 it is    
even more helpless to answer them than  
to determine how life first came2 its   
experience does not reach so far4       
,science can examine the present        
conditions of physical life1 but whether
 or no that life can undergo a change   
greater than that which passed upon the 
old inorganic world1 it cannot          
determine4 ,it has no experience4  ,but 
if ,science is dumb1 if the utmost      
exertion of human energy and power of   
research can throw no light on a future 
of which we have no experience1 we are  
not left without an answer4 ,a voice has
 been heard1 the voice of the ,son of   
,god ,himself3  ,i am the ,resurrection 
and the ,life4 ,he that believeth on    
,me1 though he were dead1 yet shall he  
live4  ,and accepting ,his word1 the    

,church in all ages1 and among all      
nations1 peoples1 and tongues1 has made 
reply3  ,i ,,look ,,for ,,the           
,,resurrection ,,of ,,the ,,dead ,,and  
,,the ,,life ,,of ,,the ,,world ,,to    
,,come4     ,,index     ,abbot1 ,c4 ,g41
 #bg1 #cd    ,albedo of ,earth1 #ed1 #ha
     ---- ,jupiter1 #abg     ---- ,mars1
 #ha     ---- ,moon1 #ed    ,albumin    
sol1 #ae    ,algol-type stars1 #ce1     
#add1 #ade    ,antares1 #ch             
,antoniadi1 ,e4 ,m41 #ig1 #ajd          
,archangel1 climate of1 #hg1 #hh        
,arcturus1 #ce1 #cg    ,aristarchus1    
lunar crater1 #dh    ,astronomical unit1
 #ba    ,atmosphere of1 ,mars1 #gf      
----1 ,moon1 #ec     ----1 ,sun1 #be    
----1 ,venus1 #aab     ,barnard1 ,e4    
,e41 #hi1 #ajd    ,beer1 #fj1 #ig1 #ih  
,bond1 ,g4 ,p41 #abg1 #abh    ,brewster1
 ,sir ,david1 #d     ,calcium1 #ab1 #cf 
,callisto1 satellite of ,jupiter1 #aca  
,calory1 #bf    ,campbell1 ,w4 ,w41 #ade
    ,carbon1 #aa1 #cd1 #ch1 #ci         
,carbonic acid1 #aa    ,cassini1 #ei1   

#fj1 #acj    ,ceres1 minor planet1 #da1 
#abj1 #aba1 #abb1 #aca    ,cerulli1 ,v41
 #ajd1 #ajh    ,chromosphere1 #bh1 #bi  
,cobalt1 #cc    ,comet1 ,encke's1 #aai  
----1 ,halley's1 #aai     ----1 spectra1
 #ch    ,copernican theory1 #a          
,copper1 #cc    ,corona1 #dj            
,coxwell1 #be1 #ge1 #gi    ,cyanogen1   
#cg1 #ch    ,czapek1 ,f41 #aa1 #ac      
,darwin1 ,sir ,g4 ,h41 #aaf    ,dawes1  
,w4 ,r41 #fj1 #fc1 #ig1 #ii    ,denning1
 ,w4 ,f41 #ajd    ,dispersion1          
anomalous1 #bh    ,doppelmayer1 lunar   
crater1 #eb    ,dubois1 ,eugene1 #aee   
,eros1 minor planet1 #eg    ,europa1    
satellite of ,jupiter1 #aca    ,evans1  
,j4 ,e41 #ajg     ,faculae1 #bi1 #cj    
,fauth1 ,p41 #ej    ,flamsteed1 lunar   
crater1 #eb    ,fluorine1 #dj           
,fraunhofer1 #cc     ,galileo1 #ea1 #ei1
 #aca    ,ganymede1 satellite of        
,jupiter1 #aca1 #acb    ,gay-,lussac1   
#ge    ,glaisher1 ,j41 #be1 #ge1 #gi    
,goodacre1 ,w41 #di    ,green1 ,n4 ,e41 
#fj1 #fb1 #fc    ,greenwich ,hospital   

,school1 #ajg1 #ajh    ,gulliver's      
,travels1 #hb1 #aef     ,haeckel1 ,e41  
#ab    ,halogens1 #cf1 #dj    ,harper's 
,weekly1 #ic    ,helium1 #cg            
,herschel1 ,sir ,j41 #ed    ---- ,sir   
,w41 #bj1 #di1 #ei1 #fj1 #fa            
,hevelius1 #ea    ,hippalus1 lunar      
crater1 #eb    ,hooke1 ,r41 #ei1 #fj1   
#acj    ,huyghens1 #ei    ,hydrocarbons1
 #ch    ,hydrogen1 #aa1 #cf1 #cg1 #ch1  
#da1 #ha     ,inhabitant1 #e            
,inhabited ,worlds1 #b1 #c1 #d    ,io1  
satellite of ,jupiter1 #aca    ,iron1   
#ab1 #cc1 #cf     ,jupiter1 #abb-cb     
----1 belts1 #abg1 #abi    ----1 great  
red spot1 #acj    ----1 proper motion of
 spots1 #abi    ----1 satellites of1    
#abh1 #aca    ----1 white spots1 #abh1  
#acj     ,keeler1 ,j4 ,e41 #abb1 #abe   
,kies1 lunar crater1 #eb    ,kirchhoff1 
#cc     ,lacus ,solis1 #ig1 #ih1 #ii    
,langley1 ,s4 ,p41 #ee    ,lilliputians1
 #hb1 #hc    ,linne1 lunar crater1 #dh  
,lockyer1 ,j4 ,n41 #fj    ,lowell1 ,p41 
#fe1 #ff1 #fg1 #fi1 #ga1 #ha1 #ig1 #ih1 

#ii1 #aja1 #ajc1 #ajd1 #aje1 #ajf1      
#ajh1 #aji1 #aaj    ,lucifer1 #aaa      
,maedler1 #df1 #dh1 #fj1 #ig1 #ih       
,maginus1 lunar crater1 #df             
,magnesium1 #ab1 #cf    ,manganese1 #cc 
,mare ,fecunditatis1 #dg    ----        
,humerum1 #eb    ---- ,nubium1 #eb      
---- ,serenitatis1 #dh    ,mars1 canals 
of1 #eg-gj1 #gh1 #aja1 #ajb    ----1    
conditions of1 #ga-ie    ----1 illusions
 of1 #if-aaj    ----1 meteorology of1   
#ic-d    ----1 oases of1 #fe1 #ih1 #ii1 
#aja    ----1 thermograph of1 #ia1 #ib  
----1 winds of1 #gg    ,mendeleeff1 #ci 
,mercury1 #aad-ah    ,messier1 lunar    
crater1 #dg1 #dh    ,metabolism1 #aj1   
#aa1 #ad1 #ae1 #ch    ,millechau1 #ajd  
,milton1 #ea    ,mira ,ceti1 #aej       
,molesworth1 ,p4 ,b41 #di1 #ajd         
,moon1 #dc-ef    ----1 terminator of1   
#ea    ,mont ,blanc1 #be1 #gd1 #hj      
,mount ,everest1 #ge1 #hj     ,nature of
 ,vision1 #ii    ,nebulae1 spectrum of1 
#ch1 #dj    ,nebulium1 #dj    ,negative 
elements1 #cf    ,neison1 ,e41 #dh1 #ec 

,neptune1 #acb1 #ada    ,newcomb1 ,s41  
#ic1 #aji    ,nicholson1 ,j4 ,w41 #dj   
,nickel1 #cc    ,nilosyrtis1 canal on   
,mars1 #hi    ,nitrogen1 #aa1 #cg1 #ch1 
#ci     ,observatory1 ,chicago1 #dd     
----1 ,harvard ,college1 #abg    ----1  
,lick1 #abb    ----1 ,paris1 #dd        
,occultation1 #eb1 #ec    ,organic      
,life1 definition of1 #ae    ,organism1 
living1 #f-ai    ,organo-genetic        
elements1 #ab1 #ch1 #ci    ,osmosis1 #ae
    ,oxygen1 #aa1 #cf1 #cg1 #ch1 #da    
,periodic ,law1 ,mendeleeff's1 #ci      
,phillips1 ,t4 ,e4 ,r41 #ajd            
,phosphorus1 #ab    ,photosphere1 #bh1  
#cc1 #cf    ,pickering1 ,w4 ,h41 #dg1   
#dh1 #ec1 #aji    ,pithecanthropus1 #aee
    ,planetary statistics1 table of1    
#gb1 #gc1 #ace    ,platinum1 #cf        
,plurality of ,worlds1 #b    ,pollock1  
,master1 #aji    ,potassium1 #ab        
,poynting1 ,j4 ,h41 #hf1 #hg1 #hi1 #aae 
,proctor1 ,r4 ,a41 #cd1 #gg             
,prominences1 #bi1 #cj1 #cg             
,protofluorine1 #dj    ,protonilus1     

canal on ,mars1 #hi    ,protoplasm1 #aa1
 #ab1 #ac1 #ae1 #ch1 #dj1 #aed          
,pyramid1 ,great1 #de     ,refraction1  
anomalous1 #bh    ,reversing layer1 #cf 
,rice-grains1 of ,sun's surface1 #bh1   
#bi    ,ring ,nebula in ,lyra1 #dj      
,rosse1 ,lord1 #ee    ,ruskin1 ,j41 #ai 
,saturn1 #acb    ----1 ,rings of1 #ach  
,schiaparelli1 ,g4 ,v41 #fa1 #fb1 #fc1  
#fd1 #ff1 #ig1 #ii1 #ajg1 #ajh1 #aaf1   
#aag    ,schooling1 ,t4 ,holt1 #hc      
,scientia1 #ff    ,semi-suns1 #aca1 #acb
    ,serviss1 ,garrett ,p41 #ag         
,singapore1 climate of1 #hg1 #hh        
,sinus ,sabaeus1 marking on ,mars1 #ig1 
#ii    ,sirius1 #cg    ,sodium1 #cc1 #cf
    ,solar ,constant1 #bf               
,spectroscopic binaries1 #add1 #ade     
,spectrum1 #ec    ----1 heat1 #ee       
,spurious disc1 #ajc    ,stars1 double1 
#ce    ----1 multiple1 #ce    ----1 red1
 #ch    ----1 spectra of1 #cd1 #ch1 #ci 
,stefan's ,law1 #he    ,stoney1 ,g4     
,johnstone1 #cd    ,streaming1 #ae      
,sulphur1 #aa1 #ch    ,sun1 #bj-cb      

,sunspots1 #bi1 #cj1 #ca1 #ch    ----1  
spectra of1 #cg    ,swift1 ,dean1 #hb1  
#aef     ,table ,mountain1 #ed          
,thermograph of ,mars1 #ia1 #ib         
,titanium1 #cf1 #cg1 #ch    ,tornadoes1 
#ca1 #acg    ,twinkler1 #aad    ,tycho1 
lunar crater1 #df     ,uranus1 #acb1    
#adj     ,venus1 #eg1 #aaa-ah           
,verworn1 ,max1 #g    ,very1 ,f4 ,w41   
#ee    ,vesper1 #aaa    ,victoria1      
hypothetical planet1 #hc     ,wallace1  
,a4 ,r41 #d    ,war of the ,worlds1     
#ajd1 #aef    ,waste1 #aea1 #aeb        
,water1 indispensable factor1 #ae1 #da  
,wells1 ,h4 ,g41 #ajd1 #aef    ,whewell1
 #d    ,williams1 ,a4 ,stanley1 #ajd    
,wolf1 ,max1 #dj     ,young1 ,c4 ,a41   
#bf1 #cc   ,,william ,,brendon ,,and    
,,son1 ,,ltd4  ,,printers1 ,,plymouth   
,footnotes3  #a ,chemical ,phenomena in 
,life1 pp4 #fb-c1 by ,dr4 ,frederick    
,czapek 7,harper's ,library of ,living  
,thought74 ,the reader is strongly      
recommended to study this work in the   
present connection4  #b ,wonders of     

,life1 by ,ernst ,haeckel1 ,professor at
 ,jena ,university1 p4 #acj4  #c        
,wonders of ,life1 pp4 #abg-h4  #d      
,chemical ,phenomena in ,life1 p4 #eh4  
#e ,ibid41 p4 #bb4  #f ,other ,worlds1  
by ,garrett ,p4 ,serviss1 pp4 #fc-d4  #g
 ,modern ,painters1 by ,john ,ruskin4   
#h ,if this experiment could be carried 
out1 it would be necessary to use a     
spring balance4 ,if the object were     
weighed in a pair of scales or by a     
steelyard1 the counterbalancing weights 
would be likewise affected in the same  
proportion1 so that the equilibrium     
would be undisturbed4  #i ,the movements
 of not a few double stars point to     
perturbations caused by the attraction  
of unseen bodies4 ,there are also a     
number of instances known of ,eclipse or
 ,algol-type variable stars1 in which   
the presence of a dark companion is     
indicated by the diminution of the light
 of the star at regular intervals4  #aj 
,proc4 ,r4 ,soc41 ,,lxxx1 #ej1 #aijg4   
#aa ,nature1 ,,lxxx1 #aeh 7,april #hth1 

#aiji74  #ab ,periodic ,changes upon the
 ,moon1 ,memoirs1 ,british ,astronomical
 ,association1 ,vol4 ,,xiii1 p4 #hh4    
#ac ,the ,moon1 by ,philip ,fauth1 p4   
#aef4  #ad ,radiation in the ,solar     
,system3 ,its ,effects on ,temperature1 
and its ,pressure on ,small ,bodies1 by 
,dr4 ,j4 ,h4 ,poynting 7,phil4 ,trans4  
of the ,royal ,society1 ,vol4 #bjb ,a74 
#ae ,publ4 of the ,astron4 ,soc4 of the 
,pacific1 ,vol4 ,,ii1 pp4 #bhf-h4       
,harper's ,library of ,living ,though   
,,arthur ,,holmes  ,,the ,,age ,,of     
,,the ,,earth  ,and ,associated         
,problems4 ,illustrated  ,gives us the  
result of the latest research into this 
field of enquiry4 ,the radioactive      
minerals are shown to be recording their
 own age with the exquisite accuracy of 
a chronometer--their records checking   
physical1 astronomical1 and geological  
methods of computation4   ,,prof4 ,a4   
,w4 ,,bickerton  ,,the ,,birth ,,of     
,,worlds ,,and ,,systems  ,illustrated  
,preface by ,prof4 ,ernest ,rutherford1 

,f4,r4,s4  ,a graphic account of the    
formation of new stars from the         
collision of dead suns or other         
celestial bodies4 ,the theory throws    
light on many astronomical problems1 and
 with its conception of an immortal     
cosmos1 is of great philosophical       
importance4   ,,prof4 ,,svante          
,,arrhenius  ,,the ,,life ,,of ,,the    
,,universe  #b ,vols4 ,illustrated  ,we 
can thoroughly recommend these volumes4 
,the information is accurate1 useful1   
and most suggestive4 ,there are many for
 whom the first chapters of ,genesis are
 a subtle allegory covering the         
profoundest truths1 and we are grateful 
to the author for having set out this   
mass of facts4--,the ,globe4   ,,sir    
,,oliver ,,lodge1 ,f4,r4,s4  ,,the      
,,ether ,,of ,,space  ,illustrated      
,this work by the great physicist will  
be found to possess an abiding charm and
 an intellectual stimulation4-,observer4
  ,opens up new views into the nature of
 the universe4 ,precise and lucid1 it   

summarises our knowledge of the         
substance which fills all space and     
penetrates all matter--the substratum of
 matter itself4--,birmingham ,post4     
,please write for announcements and     
descriptive list3  ,,harper  ,,brothers1
 #de ,albemarle ,street1 ,london1 ,w4   
,harper's ,library of ,living ,thought  
,foolscap #hvo1 gilt tops1 decorative   
covers1 richly gilt backs ,per ,volume3 
,cloth #bs4 #f;d4 net4 ,leather #cs4    
#f;d4 net4   ,,prof4 ,,arthur ,,keith1  
,m4,d4  7,hunterian ,professor ,royal   
,college of ,surgeons7  ,,ancient       
,,types ,,of ,,man  ,illustrated  ,the  
kind of book that only a master of his  
subject could write4 ,it must interest  
every thinking person4--,british        
,medical ,journal4   ,,prof4 ,,frederick
 ,,czapek  ,,chemical ,,phenomena ,,in  
,,life  ,discusses in clear1 concise    
terms the great question--,can life be  
explained by physics and chemistry8 ,it 
deals with the life-processes of plants1
 the molecular structure of protoplasm1 

organic synthesis in the cell1 the      
nature of ferments1 and the subject of  
inheritance4   ,,sir ,a4 ,,tilden1      
,f4,r4,s4  ,,the ,,elements             
,speculations as to their ,nature and   
,origin  ,diagrams1 c4  ,points to the  
conclusion that the elements resulted   
from a change in some primal essence1   
and discusses whether all may not be    
suffering a slow waste1 which1 in the   
long run1 must lead back to the primal  
chaos4   ,,sir ,,william ,,ramsay1      
,f4,r4,s4  ,,elements ,,and ,,electrons 
,diagrams  ,the electron--the atom of   
electricity--is shown to be separable   
from matter1 and to be capable under    
certain circumstances of independent    
existence4 ,the book shows that the     
electron must be regarded as a kind of  
element itself1 with much stronger      
claims to elementary or undecomposable  
characters than the bodies hitherto     
ranked as elements4     ,transcriber's  
,notes3  ,passages in italics are       
indicated by italics4  ,superscripted   

characters are indicated by superscript4
  ,the original text includes symbols   
which are represented by ,symbol in this
 text version4