568 CORAL FORMATIONS. April, 1836. 



of elevation, but that we possessed no means of knowing it. 

 I conceive it is by eliminating this source of doubt, that the 

 alternate bands of opposite movement, deduced from the 

 configuration of the reefs, directly bear on this law. I need 

 not do more than simply state, that we thus obtain (if the 

 view is correct) a means of forming some judgment of the 

 prevailing movements, during the formation of even the oldest 

 series, where volcanic rocks occur interstratified with sedi- 

 mentary deposits. 



Any thing which throws Ught on the movements of the 

 ground is well worthy of consideration ; and the history of 

 coral reefs may, in another manner, elucidate such changes 

 in the older formations. As there is every reason to believe 

 that the lamelliform corals grow only abundantly at a small 

 depth, we may feel sure, where a great thickness of coral 

 limestone occurs, that the reefs on which the zoophytes 

 flourished, must have been sinking. Until we are enabled to 

 judge by some means what were the prevailing movements 

 at different epochs, it will scarcely ever be possible to 

 speculate with any safety on the circumstances under 

 which the complicated European formations, composed of 

 such different materials and in such different states, were 

 accumulated. 



Nor can I quite pass over the probabihty of the above 

 views illustrating those admirable laws first brought forward 

 by Mr. Lyell, — of the geographical distribution of plants and 

 animals, as consequent on geological changes. M. Lesson 

 has remarked on the singular uniformity* of the Indio-Poly- 

 nesian Flora throughout the immense area of the Pacific ; — 

 the dispersion of forms having been directed against the 

 course of the trade-wind. If we believe that lagoon islands, 

 those monuments raised by infinite numbers of minute 

 architects, record the former existence of an archipelago 

 or continent in the central part of Polynesia, whence the 



* Perhaps this is stated rather too strongly ; but M. Lesson, of course, 

 had grounds for his assertion. 



