I SO [Proc. B.N.F.C., 



of the water dropping from the roofs upon the floors. The petrify- 

 ing and fossilising power of water having been described, it was 

 stated as the reader's opinion that the silicification of soft substances 

 like the bodies of echinoderms, mollusca, and sponges, had been 

 effected by a kind of endosmose, the body of the animal acting as 

 a sort of membrane, and retaining silica, which is a colloidal sub- 

 stance when in the soluble state. How it became changed to the 

 hard and insoluble variety, is a problem still requiring elucidation. 

 The formation of the particles of pisolitic and oolitic rocks, 

 and the cementing together of the mineral constituents of all 

 water-formed accumulations, depend upon the solvent action of 

 water, and its power of precipitating salts from solution, as it 

 trickles among these solid particles. Its mechanical force as a 

 moving liquid constituting it at once a destructive and a renovat- 

 ing agent having been dwelt upon, a concluding reference was 

 made to the oceans, lakes, and rivers of the globe as forming a 

 world in which numberless forms of life abound. Late soundings 

 have shown that organisms exist at nearly all depths. The tiniest 

 creatures in the ocean have produced most extensive and impor- 

 tant masses of rock; for example, beds of Chalk, which consist of 

 the limestone remains of microscopic Foraminifera ; and also Coral 

 Reefs, some of which are as much as a thousand miles in length. Di- 

 atoms, a kind of microscopic vegetables, with flinty coverings, have 

 produced effects quite as marvellous. These lowly organisms — 

 some animal and others vegetable — can propagate themselves 

 with astonishing rapidity, and it is part of their vital processes 

 to separate from solution carbonate of lime or silica, according to 

 their nature. As a parallel to Archimedes, who said " he could 

 move the earth if he had a lever long enough and a proper ful- 

 crum," Bischof has said, " Give us a mailed animalcule, and with 

 it we will in a short time separate all the limestone and flint from 

 the ocean." 



