720 REPORT— 1888. 



will grow more on the outside than on the inside, for the reasons advanced in 

 the address which had opened the discussion. He failed to grasp that there was 

 any antagonism whatever between the two views. The points raised in the open- 

 ing address were, for the most part, points which had been proved over and over 

 again by the series of observations made by Professor Agassiz and recently pub- 

 lished. He failed to see that the minus-subsidence theory was really applicable to 

 the formation of all coral reefs, and be observed. the care with which the gentleman 

 who had brought the subject before them that morning had stated that atolls and 

 barrier reefs might be made without subsidence. Of course they might. And he 

 felt sure that if Mr. Darwin were there that day he would have been amongst 

 the first to realise that the theory which he sketched out was capable of modifica- 

 tion by the advance of knowledge and the extension of research. Such then was 

 the main point which occurred to him to bring before them in that discussion. He 

 felt that he was unable to impart into *it any matters of controversial interest. 

 And he doubted whether Mr. Murray would venture to assert that there were no 

 reefs which had been formed on the Darwinian hypothesis, and he felt sure none of 

 his disciples would be rash enough to say that all these observations made during 

 the last few years could be said not to modify the views held so many years ago. 

 There was, however, one other point he would like to mention. He felt equally 

 with Professor Hickson the difficulty of accounting for the existence of atolls by 

 what he might call the carbonic-acid or erosion theory. So far as he understood this 

 theory, it largely depended upon the amount of coral in the water and upon the 

 area upon which the attack was made. In the case of atolls, so far as he knew, most 

 of them were without any of those scourings which would allow of material being 

 carried away in solution by the action of carbonic acid. Of course the action 

 might go on to a considerable extent, the action was going on incessantly, so that in 

 place of having large, thick masses of perfectly recognisable coral you find masses of 

 limestone scarcely to be distinguished for the most part from some of those reefs. 



Mr. BoTJKNE followed with a paper, in which he upheld the arguments of Mr. 

 Iliclison. 



Dr. Evans said he was present as a member of Section C, and not as one who had 

 paid any particidar regard to the formation of coral reefs. He came there for 

 instruction, and he had received it, and the general result was that, whether land 

 was rising or falling — and they as geologists knew that a see-saw action was 

 going on in dift'erent parts of the world — they knew it was possible for these coral 

 reefs at all events to be formed. Where there was a supply of food, there the 

 corals would thrive, and where there was a single nucleus there would be a gradual 

 extension in all directions. The difficulty had been to account for the ring-shape 

 of the atolls, and there had been little brought forward that day to satisfactorily 

 accoimt for that phenomenon. It might be doubted whether they were able to 

 account for the action of the carbonic acid in the water ; but they had been told 

 that all the reefs were exposed to that action. To his mind this was due to another 

 and different cause which had not been brought before them, viz., to the rainfall 

 in the districts in which these coral islands and atolls are situated. He thought 

 be was right in stating that, as a rule, water more or less fresh was to be found at a 

 certain depth in almost all the islands. That water must have come from the 

 surface in the shape of rain. Rain falling on vegetable matter would become 

 charged with carbonic acid and woidd dissolve the rock on whlcii it fell. He 

 thought they might fairly assume that the continual process of fresh water falling 

 upon the coral and finding its way out into the sea in a different condition, being 

 ciiarged with carbonate of lime, would account for the rottenness of the centre of 

 the islands and the formation of lagoons within them. That was an element 

 which he thought should not be left out, and as it had not been cited in the 

 discussion he thought it but right to bring it before them. 



The Chaikman said that from a botanical point of view he rather distrusted 

 any general theory that coral islands were of no great antiquity. The botanical 

 evidence, so far as it went, did not very strongly support INIr. Bourne's argument. 



Professor Seelet observed that, when Dr. Hickson laid before them his clear 

 statement of the views held with regard to coral reefs, he opened with expressing 



