226 CORAL AND ATOLLS 



repressive agency in the present closing scene of the atoll. 

 The accumulation of coral debris is too patent a fact. When 

 we walk through a field of Madrepore and sink knee-deep into 

 the friable debris of many preceding generations of this coral, 

 we realise the fact that dead coral accumulates and is but 

 partially removed in solution. Still there can be no doubt, as 

 shown by Murray, Irvine, J. G. Koss and others, that the 

 solvent action of sea water has a repressive effect on the rate 

 of reef growth." 



Dr. Guppy, in the course of his examination of this atoll, 

 made an important contribution to the study of coral structures 

 by formulating a very definite theory to account for the pre- 

 valent shape of the constituent islands of the atoll ring; this 

 theory will be mentioned again, for it affords a valuable addition 

 to our knowledge of coral formations. 



Since the theory of Solution, in some of these modified 

 forms, is the one that obtains the greatest general acceptance at 

 the present day, it is necessary to examine its virtues, and its 

 shortcomings, in some detail. The theory is put forward to 

 explain (1) the formation of the original lagoon, and (=2) how 

 that lagoon " becomes widened and deepened." 



With regard to (1), I think that the theory does not in 

 reality offer an explanation of the method of atoll formation, 

 and with regard to (2), the condition that it would explain is 

 contrary to experience, for atoll lagoons tend, as a rule, to 

 become smaller and shallower. 



Then, even if the conditions presumed to be brought about 

 by this agency were conditions that experience showed to be 

 real, there is no definite proof that this agency could bring 

 them about ; there is, so far as I can see in the published 

 writings of the advocates of this theory, no direct observation 

 of the working of " solution " made actually in an atoll lagoon. 

 Sir John Murray, in his original paper of 1880, at p. 511, says 

 " larger quantities of lime are carried away in solution as a 

 bicarbonate from the lagoon than are secreted by the animals 

 which can still live in it." In a paper published in 1890 * he 



* Hurray and Irvine, Nature, June 12. 



