CORAL AND CORAL REEFS 411 



why. The coral polype, like everything else, takes a certain 

 time to grow to its full size ; it does not do it in a minute ; 

 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 skeleton. Consequently every particle 

 of coral limestone is an expression of time. It must have 

 taken a certain time to separate the lime from the sea water. 

 It is not possible to arrive at an accurate computation of 

 the time it must have taken to form these coral islands, 

 because we lack the necessary data ; but we can form a 

 rough calculation, which leads to very curious and striking 

 results. The computations of the rate at which corals grow 

 are so exceedingly variable, that we must allow the widest 

 possible margin for error ; and it is better in this case 

 to make the allowance upon the side of excess. 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 probable, if I say that an inch of coral limestone 

 may be added to one of these reefs in the course of a year. 

 I think most naturalists would be inclined to laugh at me 

 for making such an assumption, and would put the growth 

 at certainly not more than half that amount. But sup- 

 posing it is so, what a very curious notion of the antiquity 

 of some of these great living pyramids comes out by a very 

 simple calculation. There is no doubt whatever that 

 the sea faces of some of them are fully a thousand feet 

 high, and if you take the reckoning of an inch a year, that 

 will give you 12,000 years for the age of that particular 

 pyramid or cone of coral limestone ; 12,000 long years have 

 these creatures been labouring in conditions which must 

 have been substantially the same as they are now, otherwise 

 the polypes could not have continued their work. But I 

 believe I very much understate both the height of some of 

 these masses, and overstate the amount which these animals 

 can form in the course of a year ; so that you might very 

 safely double the period as the time during which the 

 Pacific Ocean, the general state of the climate, and the sea, 

 and the temperature has been substantially what it is 

 now ; and yet that state of things which now obtains in the 

 Pacific Ocean is the yesterday of the history of the life of 

 the globe. Those pyramids of coral rock are built upon a 

 foundation which is itself formed by the deposits which 

 the geologist has to deal with. If we go back in time 

 and search through the series of the rocks, we find at every 



