SOME AXIMAL ARCHITECTS. 147 



-ment of knowledge as of supreme consequence to man's 

 welfare. Mr. Darwin spent some five or six years of his 

 life (1831-36) as naturalist on board H.M.S. Beagle under 

 Captain Fitzroy, and was thus enabled to study the coral- 

 polypes and their work in the most direct and advantageous 

 manner; whilst Mr. Dana, representing the scientific leader 

 of an American circumnavigating expedition (1838-42) 

 under Captain (now Admiral) Wilkes, may be regarded as an 

 authority of equal rank with Mr. Darwin on the subject of 

 coral-reefs. It is worthy of remark that, whilst Mr. Darwin's 

 observations were published in 1842, Mr. Dana's report on 

 coral-reefs was then in manuscript, but the conclusions at 

 which these observers arrived, independently of one another, 

 were of essentially identical kind, and the fact speaks power- 

 fully for the implied correctness of the views promulgated 

 by these explorers. Mr. Darwin's theory, besides offering a 

 consistent explanation of all the facts of coral life, serves in 

 the most direct manner to correlate and connect in the most 

 natural fashion the various forms of coral-reefs. Starting 

 with the assumption, already seen to rest on the most solid 

 evidence, that coral life is limited to 150 feet as a maximum 

 depth, Mr. Darwin rests his theory of the origin of reefs on 

 the fact that land subsides. 



The recognition of the geological phenomena known as 

 the subsidence or sinking of land forms the key-note of Mr. 

 Darwin's views ; and it may therefore be viewed as a pardon- 

 able digression, if the nature of these phenomena is in the 

 present instance briefly explained. That land rises and 

 sinks is a fact well known to the geologist, who can point 

 to many areas of the earth's surface in proof of his state- 

 ment. Every one conversant with the elements of geology 

 knows that the majority of the rocks composing the crust of 

 the globe have been formed under water, and that a process 

 of elevation must be assumed to account for their present 

 position. Thus, true chalk is a rock composed of the re- 

 mains of the minute foraminiferous shells already noticed. 

 The cretaceous rocks were deposited in the sea-beds of the 



