I/O Recent Views r-egarding Coral Reefs. [Sess. 



III.— REGENT VIEWS REGARDING CORAL REEFS. 



By Mr GOODCHILD 

 OF THE Geological Survey, Royal Scottish Museum. 



{Read Dec. 21, 1904.) 



There is a very close resemblance between the animals that 

 build coral structures and the common types of Sea- Anemone. 

 Coral polyps, however, secrete some kind of hard matter out of 

 the sea-water in which they live, and that structure remains 

 after the death of the animal ; whereas a Sea- Anemone leaves 

 no such hard structure behind after death. In the best 

 known types of corals (for there are at least four great groups 

 of such organisms) the durable matter referred to consists 

 mostly of carbonate of lime. In some of the less known 

 groups the structures are horny, or even leathery, in consist- 

 ency ; but with these we have here no special concern. 



The history of the carbonate of lime just referred to 

 possesses many points of interest, some of which deserve 

 notice here. In this connection it may be well to state at 

 once that the carbonate of lime which forms the stony matter 

 which is usually regarded as " coral " is not taken directly 

 from the carbonate of lime in sea- water, as one might 

 naturally have tliought would be the case, but is made out of 

 the sulphate. Some figures bearing upon this matter may 

 usefully be given here. Most of them are taken from the 

 results of the Challenger Expedition and from various papers 

 by Sir John Murray. The quantity of carbonate of lime 

 present in sea-water is extremely small. On the other hand, 

 the quantity present in river- water, basing that estimate upon 

 the average presented by nineteen principal rivers of the 

 globe, is 326,710 tons per cubic mile of the river- water. 

 It may be remarked here that, as regards the present-day 

 source of that carbonate of lime, it is derived chiefly from 

 the limestones on the land ; though basic eruptive rocks, by 

 their decomposition, still furnish part of the materials, and 

 doubtless at an early period of the Earth's history they 

 supplied nearly the whole of it. From both the limestones 



