MR. DARWIN'S REEF-FORMATION THEORIES. 77 



appears actually to have been the case in some parts of the West Indian Sea. But in 

 the form and disposition of the groups of atolls there is nothing to countenance this notion ; 

 and the assumption that a number of immense piles of sediment have been heaped on the 

 floor of the great Pacific and Indian Oceans in their central parts, far remote from land, 

 where the dark blue colour of the limpid water bespeaks its purity, cannot for one moment be 

 admitted.* 



"The many widely scattered atolls must therefore rest on rocky bases. But we cannot 

 believe that a broad mountain summit lies buried at the depth of a few fathoms beneath every 

 atoll, and nevertheless that throughout the immense area above named, not one point of rock 

 projects above the level of the sea. Even if it be assumed, without any evidence, that the 

 reef-building corals can flourish at a depth of one hundred fathoms, yet the weight of the 

 above argument is but little diminished ; for it is almost equally improbable, that as many 

 submarine mountains as there are low islands in the several great and widely-separated areas 

 above specified, should all rise within six hundred feet of the surface of the sea and not one 

 above it, as that they should be of the same height within the smaller limit of one or two 

 hundred feet. So highly improbable is this supposition, that we are compelled to believe that 

 the rocky foundations of the many atolls were never, at any one period, all submerged 

 within the depth of a few fathoms beneath the surface, but that they were brought into the 

 requisite position or level, some at one period and some at another, through movements in 

 the earth's crust. But this could not have been effected by elevation ; for the belief that points 

 so numerous and so widel}' separated were successively uplifted to a certain level, but that 

 not one point was raised above that level, is quite as improbable as the former supposition, 

 and indeed differs little from it. . . . If, then, the foundations of the many atolls were 

 not uplifted into the requisite position, they must of necessity have subsided into it, and this 

 at once solves every difficulty, for we may safely infer from the facts already submitted that 

 during a gradual subsidence the corals would be favourably' circumstanced for building up 

 their solid frameworks and reaching the surface, as island alter island slowly disappeared. 

 Thus areas of immense extent in the central and most profound parts of the great oceans might 

 become interspersed with coral islets, none of which would rise to a greater height than that 

 attained by detritus heaped up by the sea, and nevertheless they might all have been formed 

 by corals, which absolutely require for their growth a solid foundation within a few fathoms 

 of the surface." 



As frankly conceded by Mr. Darwin, there is very little direct evidence to prove the 

 phenomenon of a subsiding movement throughout the areas referred to, though such testimony 

 as is adduced points strongly in that direction. Among the facts that he cites in favour of the 



* This theory, which is in direct opposition to Mr. Darwin's, is, as will be hereafter seen, that which has recently 

 been most vigorously upheld. 



