,,coral ,,and ,,coral ,,reefs  by       
,thomas ,h4 ,huxley  #a   ,,the subject 
upon which ,i wish to address you       
to-night is the structure and origin of 
,coral and ,coral ,reefs4 ,under the    
head of coral there are included two    
very different things2 one of them is   
that substance which ,i imagine a great 
number of us have champed when we were  
very much younger than we are now1--the 
common red coral1 which is used so much1
 as you know1 for the edification and   
the delectation of children of tender   
years1 and is also employed for the     
purposes of ornament for those who are  
much older1 and as some think might know
 better4 ,the other kind of coral is a  
very different substance2 it may for    
distinction's sake be called the white  
coral2 it is a material which most      
assuredly not the hardest-hearted of    
baby farmers would give to a baby to    
chew1 and it is a substance which is to 
be seen only in the cabinets of curious 
persons1 or in museums1 or1 may be1 over

 the mantelpieces of sea-faring men4    
,but although the red coral1 as ,i have 
mentioned to you1 has access to the very
 best society2 and although the white   
coral is comparatively a despised       
product1 yet in this1 as in many other  
cases1 the humbler thing is in reality  
the greater2 the amount of work which is
 done in the world by the white coral   
being absolutely infinite compared with 
that effected by its delicate and       
pampered namesake4 ,each of these       
substances1 the white coral and the red1
 however1 has a relationship to the     
other4 ,they are1 in a zoological sense1
 cousins1 each of them being formed by  
the same kind of animals in what is     
substantially the same way4 ,each of    
these bodies is1 in fact1 the hard      
skeleton of a very curious and a very   
simple animal1 more comparable to the   
bones of such animals as ourselves than 
to the shells of oysters or creatures of
 that kind2 for it is the hardening of  
the internal tissue of the creature1 of 

its internal substance1 by the deposit  
in the body of a material which is      
exceedingly common1 not only in fresh   
but in sea water1 and which is specially
 abundant in those waters which we know 
as hard1 those waters1 for example1     
which leave a fur upon the bottom of a  
tea-kettle4 ,this fur is carbonate of   
lime1 the same sort of substance as     
limestone and chalk4 ,that material is  
contained in solution in sea water1 and 
it is out of the sea water in which     
these coral creatures live that they get
 the lime which is needed for the       
forming of their hard skeleton4  ,but   
now what manner of creatures are these  
which form these hard skeletons8 ,i dare
 say that in these days of keeping      
aquaria1 of locomotion to the sea-side1 
most of those whom ,i am addressing may 
have seen one of those creatures which  
used to be known as the sea anemone1    
receiving that name on account of its   
general resemblance1 in a rough sort of 
way1 to the flower which is known as the

 anemone2 but being a thing which lives 
in the sea1 it was qualified as the sea 
anemone4 ,well1 then1 you must suppose a
 body shaped like a short cylinder1 the 
top cut off1 and in the top a hole      
rather oval than round4 ,all round this 
aperture1 which is the mouth1 imagine   
that there are placed a number of       
feelers forming a circle4 ,the cavity of
 the mouth leads into a sort of stomach1
 which is very unlike those of the      
higher animals1 in the circumstance that
 it opens at the lower end into a cavity
 of the body1 and all the digested      
matter1 converted into nourishment1 is  
thus distributed through the rest of the
 body4 ,that is the general structure of
 one of these sea anemones4 ,if you     
touch it it contracts immediately into a
 heap4 ,it looks at first quite like a  
flower in the sea1 but if you touch it  
you find that it exhibits all the       
peculiarities of a living animal2 and if
 anything which can serve as its prey   
comes near its tentacles1 it closes them

 round it and sucks the material into   
its stomach and there digests it and    
turns it to the account of its own body4
  ,these creatures are very voracious1  
and not at all particular what they     
seize2 and sometimes it may be that they
 lay hold of a shellfish which is far   
too big to be packed into that interior 
cavity1 and1 of course1 in any ordinary 
animal a proceeding of this kind would  
give rise to a very severe fit of       
indigestion4 ,but this is by no means   
the case in the sea anemone1 because    
when digestive difficulties of this kind
 arise he gets out of them by splitting 
himself in two2 and then each half      
builds itself up into a fresh creature1 
and you have two polypes where there was
 previously one1 and the bone which     
stuck in the way lying between them6    
,not only can these creatures multiply  
in this fashion1 but they can multiply  
by buds4 ,a bud will grow out of the    
side of the body 7,i am not speaking of 
the common sea anemone1 but of allied   

creatures7 just like the bud of a plant1
 and that will fashion itself into a    
creature just like the parent4 ,there   
are some of them in which these buds    
remain connected together1 and you will 
soon see what would be the result of    
that4 ,if ,i make a bud grow out here1  
and another on the opposite side1 and   
each fashions itself into a new polype1 
the practical effect will be that before
 long you will see a single polype      
converted into a sort of tree or bush of
 polypes4 ,and these will all remain    
associated together1 like a kind of     
co-operative store1 which is a thing ,i 
believe you understand very well        
here1--each mouth will help to feed the 
body and each part of the body help to  
support the multifarious mouths4 ,i     
think that is as good an example of a   
zoological co-operative store as you can
 well have4 ,such are these wonderful   
creatures4 ,but they are capable not    
only of multiplying in this way1 but in 
other ways1 by having a more ordinary   

and regular kind of offspring4 ,little  
eggs are hatched and the young are      
passed out by the way of the mouth1 and 
they go swimming about as little oval   
bodies covered with a very curious kind 
of hairlike processes4 ,each of these   
processes is capable of striking water  
like an oar2 and the consequence is that
 the young creature is propelled through
 the water4 ,so that you have the young 
polype floating about in this fashion1  
covered by its 'vibratile cilia'1 as    
these long filaments1 which are capable 
of vibration are termed4 ,and thus1     
although the polype itself may be a     
fixed creature unable to move about1 it 
is able to spread its offspring over    
great areas4 ,for these creatures not   
only propel themselves1 but while       
swimming about in the sea for many      
hours1 or perhaps days1 it will be      
obvious that they must be carried hither
 and thither by the currents of the sea1
 which not unfrequently move at the rate
 of one or two miles an hour4 ,thus1 in 

the course of a few days1 the offspring 
of this stationary creature may be      
carried to a very great distance from   
its parent2 and having been so carried  
it loses these organs by which it is    
propelled1 and settles down upon the    
bottom of the sea and grows up again    
into the form and condition of its      
parents4 ,so that if you suppose a      
single polype of this kind settled upon 
the bottom of the sea1 it may by these  
various methods--that is to say1 by     
cutting itself in two1 which we call    
fission1 or by budding2 or by sending   
out these swimming embryos1--multiply   
itself to an enormous extent1 and give  
rise to thousands1 or millions1 of      
progeny in a comparatively short time2  
and these thousands1 or millions1 of    
progeny may cover a very large surface  
of the sea bottom2 in fact1 you will    
readily perceive that1 give them time1  
and there is no limit to the surface    
which they may cover4  ,having          
understood thus far the general nature  

of these polypes1 which are the         
fabricators both of the red and white   
coral1 let us consider a little more    
particularly how the skeletons of the   
red coral and of the white coral are    
formed4 ,the red coral polype perches   
upon the sea bottom1 it then grows up   
into a sort of stem1 and out of that    
stem there grow branches1 each of which 
has its own polypes2 and thus you have a
 kind of tree formed1 every branch of   
the tree terminated by its polype4 ,it  
is a tree1 but at the end of the        
branches there are open mouths of       
polypes instead of flowers4 ,thus there 
is a common soft body connecting the    
whole1 and as it grows up the soft body 
deposits in its interior a quantity of  
carbonate of lime1 which acquires a     
beautiful red or flesh colour1 and forms
 a kind of stem running through the     
whole1 and it is that stem which is the 
red coral4 ,the red coral grows         
principally at the bottom of the        
,mediterranean ,sea1 at very great      

depths1 and the coral fishers1 who are  
very adventurous seamen1 take their drag
 nets1 of a peculiar kind1 roughly made1
 but efficient for their purpose1 and   
drag them along the bottom of the sea to
 catch the branches of the red coral1   
which become entangled and are thus     
brought up to the surface4 ,they are    
then allowed to putrefy1 in order to get
 rid of the animal matter1 and the red  
coral is the skeleton that is left4  ,in
 the case of the white coral1 the       
skeleton is more complete4 ,in the red  
coral1 the skeleton belongs to the      
whole2 in the white coral there is a    
special skeleton for every one of these 
polypes in addition to that for the     
whole body4 ,there is a skeleton formed 
in the body of each of them1 like a cup 
divided by a number of radiating        
partitions towards the outside2 and that
 cup is formed of carbonate of lime1    
only not stained red1 as in the case of 
the red coral4 ,and all these cups are  
joined together into a common branch1   

the result of which is the formation of 
a beautiful coral tree4 ,this is a great
 mass of madrepore1 and in the living   
state every one of the ends of these    
branches was terminated by a beautiful  
little polype1 like a sea anemone1 and  
all the skeleton was covered by a soft  
body which united the polypes together4 
,you must understand that all this      
skeleton has been formed in the interior
 of the body1 to suit the branched body 
of the polype mass1 and that it is as   
much its skeleton as our own bones are  
our skeleton4 ,in this next coral the   
creature which has formed the skeleton  
has divided itself as it grew1 and      
consequently has formed a great         
expansion2 but scattered all over this  
surface there were polype bodies like   
those ,i previously described4 ,again1  
when this great cup was alive1 the whole
 surface was covered with a beautiful   
body upon which were set innumerable    
small polype flowers1 if we may so call 
them1 often brilliantly coloured2 and   

the whole cup was built up in the same  
fashion by the deposit of carbonate of  
lime in the interior of the combined    
polype body1 formed by budding and by   
fission in the way ,i described4 ,you   
will perceive that there is no necessary
 limit to this process4 ,there is no    
reason why we should not have coral     
three or four times as big2 and there   
are certain creatures of this kind that 
do fabricate very large masses1 or half 
spheres several feet in diameter4 ,thus 
the activity of these animals in        
separating carbonate of lime from the   
sea and building it up into definite    
shapes is very considerable indeed4     
,now ,i think ,i have said              
sufficient--as much as ,i can without   
taking you into technical details1 of   
the general nature of these creatures   
which form coral4 ,the animals which    
form coral are scattered over the seas  
of all countries in the world4 ,the red 
coral is comparatively limited1 but the 
polypes which form the white coral are  

widely scattered4 ,there are some of    
them which remain single1 or which give 
rise to only small accumulations2 and   
the skeletons of these1 as they die1    
accumulate upon the bottom of the sea1  
but they do not come to much2 they are  
washed about and do not adhere together1
 but become mixed up with the mud of the
 sea4 ,but there are certain parts of   
the world in which the coral polypes    
which live and grow are of a kind which 
remain1 adhere together1 and form great 
masses4 ,they differ from the ordinary  
polypes just in the same way as those   
plants which form a peat-bog or         
meadow-turf differ from ordinary plants4
 ,they have a habit of growing together 
in masses in the same place2 they are   
what we call gregarious things2 and the 
consequence of this is1 that as they die
 and leave their skeletons1 those       
skeletons form a considerable solid     
aggregation at the bottom of the sea1   
and other polypes perch upon them1 and  
begin building upon them1 and so by     

degrees a great mass is formed4 ,and    
just as we know there are some ancient  
cities in which you have a ,british     
city1 and over that the foundations of a
 ,roman city2 and over that a ,saxon    
city1 and over that again a modern city1
 so in these localities of which ,i am  
speaking1 you have the accumulations of 
the foundations of the houses1 if ,i may
 use the term1 of nation after nation of
 these coral polypes2 and these         
accumulations may cover a very          
considerable space1 and may rise in the 
course of time from the bottom to the   
surface of the sea4  ,mariners have a   
name which they apply to all sorts of   
obstacles consisting of hard and rocky  
matter which comes in their way in the  
course of their navigation2 they call   
such obstacles reefs1 and they have long
 been in the habit of calling the       
particular kind of reef1 which is formed
 by the accumulation of the skeletons of
 dead corals1 by the name of coral      
reefs1 therefore1 those parts of the    

world in which these accumulations occur
 have been termed by them coral reef    
areas1 or regions in which coral reefs  
are found4 ,there is a very notable     
example of a simple coral reef about the
 island of ,mauritius1 which ,i dare say
 you all know1 lies in the middle of the
 ,indian ,ocean4 ,it is a very          
considerable and beautiful island1 and  
is surrounded on all sides by a mass of 
coral1 which has been formed in the way 
,i have described2 so that if you could 
get upon the top of one of the peaks of 
the island1 and look down upon the      
,indian ,ocean1 you would see that the  
beach round the ,island was continued   
outward by a kind of shallow terrace1   
which is covered by the sea1 and where  
the sea is quite shallow2 and at a      
distance varying from three-quarters of 
a mile to a mile and a half from the    
proper beach1 you would see a line of   
foam or surf which looks most beautiful 
in contrast with the bright green water 
in the inside1 and the deep blue of the 

sea beyond4 ,that line of surf indicates
 the point at which the waters of the   
ocean are breaking upon the coral reef  
which surrounds the island4 ,you see it 
sweep round the island upon all sides1  
except where a river may chance to come 
down1 and that always makes a gap in the
 shore4  ,there are two or three points 
which ,i wish to bring clearly before   
your notice about such a reef as this4  
,in the first place1 you perceive it    
forms a kind of fringe round the island1
 and is therefore called a fringing     
reef4 ,in the next place1 if you go out 
in a boat1 and take soundings at the    
edge of the reef1 you find that the     
depth of the water is not more than from
 #bj to #be fathoms--that is about #abj 
to #aej feet4 ,outside that point you   
come to the natural sea bottom2 but all 
inside that depth is coral1 built up    
from the bottom by the accumulation of  
the skeletons of innumerable generations
 of coral polypes4 ,so that you see the 
coral forms a very considerable rampart 

round the island4 ,what the exact       
circumference may be ,i do not remember1
 but it cannot be less than #ajj miles1 
and the outward height of this wall of  
coral rock nowhere amounts to less than 
about #ajj or #aej feet4  ,when the     
outward face of the reef is examined1   
you find that the upper edge1 which is  
exposed to the wash of the sea1 and all 
the seaward face1 is covered with those 
living plant-like flowers which ,i have 
described to you4 ,they are the coral   
polypes which grow1 flourish1 and add to
 the mass of calcareous matter which    
already forms the reef4 ,but towards the
 lower part of the reef1 at a depth of  
about #abj feet1 these creatures are    
less active1 and fewer of them at work2 
and at greater depths than that you find
 no living coral polype at all2 and it  
may be laid down as a rule1 derived from
 very extensive observation1 that these 
reef-building corals cannot live in a   
greater depth of water than about #abj  
to #aej feet4 ,i beg you to recollect   

that fact1 because it is one ,i shall   
have to come back to by and by1 and to  
show to what very curious consequences  
that rule leads4 ,well then1 coming back
 to the margin of the reef1 you find    
that part of it which lies just within  
the surf to be coated by a very curious 
plant1 a sort of seaweed1 which contains
 in its substance a very great deal of  
carbonate of lime1 and looks almost like
 rock2 this is what is called the nulli 
pore4 ,more towards the land1 we come to
 the shallow water upon the inside of   
the reef1 which has a particular name1  
derived from the ,spanish or the        
,portuguese--it is called a lagoon1 or  
lake4 ,in this lagoon there is          
comparatively little living coral2 the  
bottom of it is formed of coral mud4 ,if
 we pounded this coral in water1 it     
would be converted into calcareous mud1 
and the waves during storms do for the  
coral skeletons exactly what we might do
 for this coral in a mortar2 the waves  
tear off great fragments and crush them 

with prodigious force1 until they are   
ground into the merest powder1 and that 
powder is washed into the interior of   
the lagoon1 and forms a muddy coating at
 the bottom4 ,beside that there are a   
great many animals that prey upon the   
coral--fishes1 worms1 and creatures of  
that kind1 and all these1 by their      
digestive processes1 reduce the coral to
 the same state1 and contribute a very  
important element to this fine mud4 ,the
 living coral found in the lagoon1 is   
not the reef building coral2 it does not
 give rise to the same massive          
skeletons4 ,as you go in a boat over    
these shallow pools1 you see these      
beautiful things1 coloured red1 blue1   
green1 and all colours1 building their  
houses2 but these are mere tenements1   
and not to be compared in magnitude and 
importance to the masses which are built
 by the reef-builders themselves4 ,now  
such a structure as this is what is     
termed a fringing reef4 ,you meet with  
fringing reefs of this kind not only in 

the ,mauritius1 but in a number of other
 parts of the world4 ,if these were the 
only reefs to be seen anywhere1 the     
problem of the formation of coral reefs 
would never have been a difficult one4  
,nothing can be easier than to          
understand how there must have been a   
time when the coral polypes came and    
settled on the shores of this island1   
everywhere within the #bj to #be fathom 
line1 and how1 having perched there1    
they gradually grew until they built up 
the reef4  ,but these are by no means   
the only sort of coral reefs in the     
world2 on the contrary1 there are very  
large areas1 not only of the ,indian    
ocean1 but of the ,pacific1 in which    
many many thousands of square miles are 
covered either with a peculiar kind of  
reef1 which is called the encircling    
reef1 or by a still more curious reef   
which goes by the name of the atoll4    
,there is a very good picture1 which    
,professor ,roscoe has been kind enough 
to prepare for me1 of one of these      

atolls1 which will enable you to form a 
notion of it as a landscape4 ,you have  
in the foreground the waters of the     
,pacific4 ,you must fancy yourself in   
the middle of the great ocean1 and you  
will perceive that there is an almost   
circular island1 with a low beach1 which
 is formed entirely of coral sand2      
growing upon that beach you have        
vegetation1 which takes1 of course1 the 
shape of the circular land2 and then1 in
 the interior of the circle1 there is a 
pool of water1 which is not very        
deep--probably in this case not more    
than eight or nine fathoms--and which   
forms a strange and beautiful contrast  
to the deep blue water outside4 ,this   
circular island1 or atoll1 with a lagoon
 in the middle1 is not a complete       
circle2 upon one side of it there is a  
break1 exactly like the entrance into a 
dock2 and1 as a matter of course1 these 
circular islets1 or atolls1 form most   
efficient break-waters1 for if you can  
only get inside your ship is in perfect 

safety1 with admirable anchorage in the 
interior4 ,if the ship were lying within
 a mile of that beach1 the water would  
be one or two thousand feet deep2       
therefore1 a section of that atoll1 with
 the soundings as deep as this all      
round1 would give you the notion of a   
great cone1 cut off at the top1 and with
 a shallow cup in the middle of it4     
,now1 what a very singular fact this is1
 that we should have rising from the    
bottom of the deep ocean a great        
pyramid1 beside which all human pyramids
 sink into the most utter               
insignificance6 ,these singular coral   
limestone structures are very beautiful1
 especially when crowned with cocoa-nut 
trees4 ,there you see the long line of  
land1 covered with vegetation--cocoa-nut
 trees--and you have the sea upon the   
inner and outer sides1 with a vessel    
very comfortably riding at anchor4 ,that
 is one of the remarkable forms of reef 
in the ,pacific4 ,another is a sort of  
half-way house1 between the atoll and   

the fringing reef2 it is what is called 
an encircling reef4 ,in this case you   
see an ,island rising out of the sea1   
and at two or three miles distance1 or  
more1 and separated by a deep channel1  
which may be eight to twelve fathoms    
deep1 there is a reef1 which encircles  
it like a great girdle2 and outside that
 again the water is one or two thousand 
feet deep4 ,i spent three or four years 
of my life in cruising about a          
modification of one of these encircling 
reefs1 called a barrier reef1 upon the  
east coast of ,australia--one of the    
most wonderful accumulations of coral   
rock in the world4 ,it is about #a1ajj  
miles long1 and varies in width from one
 or two to many miles4 ,it is separated 
from the coast of ,australia by a       
channel of about #be fathoms deep2 while
 outside1 looking toward ,america1 the  
water is two or three thousand feet deep
 at a mile from the edge of the reef4   
,this is an accumulation of limestone   
rock1 built up by corals1 to which we   

have no parallel anywhere else4 ,imagine
 to yourself a heap of this material    
more than one thousand miles long1 and  
several miles wide4 ,that is a barrier  
reef2 but a barrier reef is merely as it
 were a fragment of an encircling reef  
running parallel to the coast of a great
 continent4  ,i told you that the       
polypes which built these reefs were not
 able to live at a greater depth than   
#bj to #be fathoms of water2 and that is
 the reason why the fringing reef goes  
no farther from the land than it does4  
,and for the same reason1 if the        
,pacific could be laid bare we should   
have a most singular spectacle4 ,there  
would be a number of mountains with     
truncated tops scattered over it1 and   
those mountains would have an appearance
 just the very reverse of that presented
 by the mountains we see on shore4 ,you 
know that the mountains on shore are    
covered with vegetation at their bases1 
while their tops are barren or covered  
with snow2 but these mountains would be 

perfectly bare at their bases1 and all  
round their tops they would be covered  
with a beautiful vegetation of coral    
polypes4 ,and not only would this be the
 case1 but we should find that for a    
considerable distance down1 all the     
material of these atoll and encircling  
reefs was built up of precisely the same
 coral rock as the fringing reef4 ,that 
is to say1 you have an enormous mass of 
coral rock at a depth below the surface 
of the water where we know perfectly    
well that the coral animals could not   
have lived to form it4 ,when those two  
facts were first put together1          
naturalists were quite as much puzzled  
as ,i daresay you are1 at present1 to   
understand how these two seeming        
contradictions could be reconciled2 and 
all sorts of odd hypotheses were        
resorted to4 ,it was supposed that the  
coral did not extend so far down1 but   
that there was a great chain of         
submarine mountains stretching through  
the ,pacific1 and that the coral had    

grown upon them4 ,but only fancy what   
supposition that was1 for you would have
 to imagine that there was a chain of   
mountains a thousand miles or more long1
 and that the top of every mountain came
 within #bj fathoms of the surface of   
the sea1 and neither rose above nor sunk
 beneath that level4 ,that is highly    
improbable3 such a chain of mountains   
was never known4 ,then how can you      
possibly account for the curious        
circular form of the atolls by any      
supposition of this kind8 ,i believe    
there was some one who imagined that all
 these mountains were volcanoes1 and    
that the reefs had grown round the tops 
of the craters1 so we all stuck fast4 ,i
 may say we1 though it was rather before
 my time4 ,and when we all stick fast1  
it is just the use of a man of genius   
that he comes and shows us the meaning  
of the thing4 ,he generally gives an    
explanation which is so ridiculously    
simple that everybody is ashamed that he
 did not find it out before2 and the way

 such a discoverer is often rewarded is 
by finding out that some one had made   
the discovery before him6 ,i do not mean
 to say that it was so in this          
particular instance1 because the great  
man who played the part of ,columbus and
 the egg on this occasion had1 ,i       
believe1 always had the full credit     
which he so well deserves4 ,the         
discoverer of the key to these problems 
was a man whose name you know very well 
in connection with other matters1 and ,i
 should not wonder if some of you have  
heard it said that he was a superficial 
kind of person who did not know much    
about the subject on which he writes4   
,he was ,mr4 ,darwin1 and this brilliant
 discovery of his was made public thirty
 years ago1 long before he became the   
celebrated man he now is2 and it was one
 of the most singular instances of that 
astonishing sagacity which he possesses 
of drawing consequences by way of       
deduction from simple principles of     
natural science--a power which has      

served him in good stead on other       
occasions4 ,well1 ,mr4 ,darwin1 looking 
at these curious difficulties and having
 that sort of knowledge of natural      
phenomena in general1 without which he  
could not have made a step towards the  
solution of the problem1 said to        
himself--,it is perfectly clear that the
 coral which forms the base of the      
atolls and fringing reefs could not     
possibly have been formed there if the  
level of the sea has always been exactly
 where it is now1 for we know for       
certain that these polypes cannot build 
at a greater depth than #bj to #be      
fathoms1 and here we find them at #ej to
 #ajj fathoms4  ,that was the first     
point to make clear4 ,the second point  
to deal with was--if the polypes cannot 
have built there while the level of the 
sea has remained stationary1 then one of
 two things must have happened--either  
the sea has gone up1 or the land has    
gone down4  ,there is no escape from one
 of these two alternatives4 ,now the    

objections to the notion of the sea     
having gone up are very considerable    
indeed2 for you will readily perceive   
that the sea could not possibly have    
risen a thousand feet in the ,pacific   
without rising pretty much the same     
distance everywhere else2 and if it had 
risen that height everywhere else since 
the reefs began to be formed1 the       
geography of the world in general must  
have been very different indeed1 at that
 time1 from what it is now4 ,and we have
 very good means of knowing that any    
such rise as this certainly has not     
taken place in the level of the sea     
since the time that the corals have been
 building their houses4 ,and so the only
 other alternative was to suppose that  
the land had gone down1 and at so slow a
 rate that the corals were able to grow 
upward as fast as it went downward4 ,you
 will see at once that this is the      
solution of the mystery1 and nothing can
 be simpler or more obvious when you    
come to think about it4 ,suppose we     

start with a coral sea and put in the   
middle of it an island such as the      
,mauritius4 ,now let the coral polypes  
come and perch on the shore and build a 
fringing reef1 which will stop when they
 come to #bj or #be fathoms1 and you    
will have a fringing reef like that     
round the island in the illustration4   
,so long as the land remains stationary1
 so long as it does not descend so long 
will that reef be unable to get any     
further out1 because the moment the     
polype embryos try to get below they    
die4 ,but now suppose that the land     
sinks very gradually indeed4 ,let it    
subside by slow degrees1 until the      
mountain peak1 which we have in the     
middle of it1 alone projects beyond the 
sea level4 ,the fringing reef would be  
carried down also2 but we suppose that  
the sinking is so slow that the coral   
polypes are able to grow up as fast as  
the land is carried down2 consequently  
they will add layer upon layer until    
they form a deep cup1 because the inner 

part of the reef grows much more slowly 
than the outer part4 ,thus you have the 
reef forming a bed thicker upon the     
flanks of the island2 but the edge of   
the reef will be very much further out  
from the land1 and the lagoon will be   
many times deeper2 in short1 your       
fringing reef will be converted into an 
encircling reef4 ,and if1 instead of    
this being an island1 it were a great   
continent like ,australia1 then you will
 have the phenomenon of a barrier reef  
which ,i have described4 ,the barrier   
reef of ,australia was originally a     
fringing reef2 the land has gone slowly 
down2 the consequence is the lagoon has 
deepened until its depth is now #be     
fathoms and the corals have grown up at 
the outer edge until you have that      
prodigious accumulation which forms the 
barrier reef at present4 ,now let this  
process go on further still2 let us take
 the land a further step down1 so as to 
submerge even the peak4 ,the coral1     
still growing up1 will cover the surface

 of the land1 and you will have an atoll
 reef2 that is to say1 a more or less   
circular or oval ring of coral rock with
 a lagoon in the middle4 ,thus you see  
that every peculiarity and phenomenon of
 these different forms of coral reef was
 explained at once by the simplest of   
all possible suppositions1 namely1 by   
supposing that the land has gone down at
 a rate not greater than that at which  
the coral polypes have grown up4 ,you   
explain a ,fringing ,reef as a reef     
which is formed round land comparatively
 stationary2 an ,encircling ,reef as one
 which is formed round land going down2 
and an ,atoll as a reef formed upon land
 gone down2 and the thing is so simple  
that a child may understand it when it  
is once explained4  ,but this would by  
no means satisfy the conditions of a    
scientific hypothesis4 ,no man who is   
cautious would dream of trusting to an  
explanation of this kind simply because 
it explained one particular set of      
facts4 ,before you can possibly be safe 

in dealing with ,nature--who is very    
properly made of the feminine gender1 on
 account of the astonishing tricks which
 she plays upon her admirers6--,i say   
before you can be safe in dealing with  
,nature1 you must get two or three kinds
 of cross proofs1 so as to make sure not
 only that your hypothesis fits that    
particular set of facts1 but that it is 
not contradicted by some other set of   
facts which is just as clear and        
certain4 ,and it so happens1 that in    
this case ,mr4 ,darwin supplied the     
cross proofs as well as the immediate   
evidence4 ,you have all heard of        
volcanoes1 those wonderful vents in the 
surface of the earth out of which pour  
masses of lava1 cinders and ashes1 and  
the like4 ,now1 it is a matter of       
observation and experience that all     
volcanoes are placed in areas in which  
the surface of the earth is undergoing  
elevation1 or at any rate is stationary2
 they are not placed in parts of the    
world in which the level of the land is 

being lowered4 ,they are all indications
 of a great subterranean activity1 of a 
something being pushed up1 and therefore
 naturally the land either gives way and
 lets it come through1 or else is raised
 up by its violence4 ,and so ,mr4       
,darwin1 being desirous not to merely   
put out a flashy hypothesis1 but to get 
at the truth of the matter1 said to     
himself1 ,if my notion of this matter is
 right1 then atolls and encircling      
reefs1 inasmuch as they are dependent   
upon subsidence1 ought not to be found  
in company with volcanoes2 and1 'vice   
versa'1 volcanoes ought not to be found 
in company with atolls1 but they ought  
to be found in company with fringing    
reefs4 ,and if you turn to ,mr4         
,darwin's great work upon the coral     
reefs1 you will see a very beautiful    
chart of the world1 which he prepared   
with great pains and labour1 showing the
 distribution on the one hand of the    
reefs1 and on the other of the          
volcanoes2 you will find that in no case

 does the atoll accompany the volcano1  
or the volcano burst up among the       
atolls4 ,it is most instructive to look 
at the great area of the ,pacific on the
 map1 and see the great masses of atolls
 forming in one region of it a most     
enormous belt1 running from north-west  
to south-east2 while the volcanoes1     
which are very numerous in that region1 
go round the margin1 so that we can     
picture the ,pacific to ourselves a     
section of a kind of very shallow       
basin--shallow in proportion to its     
width1 with the atolls rising from the  
bottom of it1 and at the margins the    
volcanoes4 ,it is exactly as if you had 
taken a flat mass and lifted up the     
edges of it2 the subterranean force     
which lifted up the edges shows itself  
in volcanoes1 and as the edges have been
 raised1 the middle part of the mass has
 gone down4 ,in other words1 the facts  
of physical geography precisely and     
exactly correspond with the hypothesis  
which accounts for the infinite         

varieties of coral reefs4  ,one other   
point1 before ,i conclude1 about this   
matter4 ,these reefs1 as you have just  
perceived1 are in a most singular and   
unexpected manner indications of        
physical changes of elevations and      
depressions going on upon the surface of
 the globe4 ,i dare say it may have     
surprised you to hear me talk in this   
familiar sort of way of land going up   
and down2 but it is one of the universal
 lessons of geology that the land is    
going down and going up1 and has been   
going up and down1 in all sorts of      
places and to all sorts of distances1   
through all recorded time4 ,geologists  
would be quite right in maintaining the 
seeming paradox that the stable thing in
 the world is the fluid sea and the     
shifting thing is the solid land4 ,that 
may sound a very hard saying at first1  
but the more you look into geology1 the 
more you will see ground for believing  
that it is not a mere paradox4  ,in an  
unexpected manner1 again1 these reefs   

afford us not only an indication of     
change of place1 but they afford an     
indication of lapse of time4 ,the reef  
is a timekeeper of a very curious       
character2 and you can easily understand
 why4 ,the coral polype1 like everything
 else1 takes a certain time to grow to  
its full size2 it does not do it in a   
minute2 just as a child takes a certain 
time to grow into a man so does the     
embryo polype take time to grow into a  
perfect polype and form its skeleton4   
,consequently every particle of coral   
limestone is an expression of time4 ,it 
must have taken a certain time to       
separate the lime from the sea water4   
,it is not possible to arrive at an     
accurate computation of the time it must
 have taken to form these coral islands1
 because we lack the necessary data2 but
 we can form a rough calculation1 which 
leads to very curious and striking      
results4 ,the computations of the rate  
at which corals grow are so exceedingly 
variable1 that we must allow the widest 

possible margin for error2 and it is    
better in this case to make the         
allowance upon the side of excess4 ,i   
think that anybody who knows anything   
about the matter will tell you that ,i  
am making a computation far in excess of
 what is probable1 if ,i say that an    
inch of coral limestone may be added to 
one of these reefs in the course of a   
year4 ,i think most naturalists would be
 inclined to laugh at me for making such
 an assumption1 and would put the growth
 at certainly not more than half that   
amount4 ,but supposing it is so1 what a 
very curious notion of the antiquity of 
some of these great living pyramids     
comes out by a very simple calculation4 
,there is no doubt whatever that the sea
 faces of some of them are fully a      
thousand feet high1 and if you take the 
reckoning of an inch a year1 that will  
give you #ab1jjj years for the age of   
that particular pyramid or cone of coral
 limestone2 #ab1jjj long years have     
these creatures been labouring in       

conditions which must have been         
substantially the same as they are now1 
otherwise the polypes could not have    
continued their work4 ,but ,i believe ,i
 very much understate both the height of
 some of these masses1 and overstate the
 amount which these animals can form in 
the course of a year2 so that you might 
very safely double the period as the    
time during which the ,pacific ,ocean1  
the general state of the climate1 and   
the sea1 and the temperature has been   
substantially what it is now2 and yet   
that state of things which now obtains  
in the ,pacific ,ocean is the yesterday 
of the history of the life of the globe4
 ,those pyramids of coral rock are built
 upon a foundation which is itself      
formed by the deposits which the        
geologist has to deal with4 ,if we go   
back in time and search through the     
series of the rocks1 we find at every   
age of the world's history which has yet
 been examined1 accumulations of        
limestone1 many of which have certainly 

been built up in just the same way as   
those coral reefs which are now forming 
the bottom of the ,pacific ,ocean4 ,and 
even if we turn to the oldest periods of
 geologic history1 although the nature  
of the materials is changed1 although we
 cannot apply to them the same          
reasonings that we can to the existing  
corals1 yet still there are vast masses 
of limestone formed of nothing else than
 the accumulations of the skeletons of  
similar animals1 and testifying that    
even in those remote periods of the     
world's history1 as now1 the order of   
things implies that the earth had       
already endured for a period of which   
our ordinary standards of chronology    
give us not the slightest conception4   
,in other words1 the history of these   
coral reefs1 traced out honestly and    
carefully1 and with the same sort of    
reasoning that you would use in the     
ordinary affairs of life1 testifies1    
like every fact that ,i know of1 to the 
prodigious antiquity of the earth since 

it existed in a condition in the main   
similar to that in which it now is4     
,footnote #a3 ,a ,lecture delivered in  
,manchester1 ,november #dth1 #ahgj4