170 Origin of Flint. 



ous formation, its origin is probably to be attributed to the same 

 cause as that of succeeding beds, whatever that may have been. 



A British government-vessel, the Challenger, is now engaged in 

 circumnavigating the globe, on a scientific exploring expedition, 

 investigating the bottom of the sea at different depths. Last autumn, 

 some importants reports of discoveries were made, and within the last 

 month Professor Huxley has delivered a lecture in London upon these 

 discoveries, and their bearing upon some imj^ortant jjroblems in geolog3\ 

 In reviewing the knowledge that existed on this subject, previous to 

 the expedition of the Challenger, he says, the world is indebted for it 

 chiefly to the researches of American ships ; that the Americans had 

 submitted the greenish mud they had taken from the bottom of the 

 Northern Sea, at 14,000 feet deep, to Ehrenberg, who had for sixteen 

 years been maintaining the paradox, that chalk was made up of the 

 shells of minute animalculae, and from this American collection he had 

 been enabled to confirm his theory ; that there was found, not only 

 vast quantities of calcareous matter, but a still larger quantity of 

 siliceous matter; that the Arctic and Antarctic waters are covered 

 with a scum of vast extent, and this scum, under microscopic exami- 

 nation, is found to be made up of two or three species of minute animals, 

 chiefly Ectdularia, Globutomaria and Foraminifera, and the lowest con- 

 ceivable plant, .a diatomaceous thing, consisting only of a protoplasmic 

 shell. The shells of these minute things, the beginnings of organization 

 on the gh)be, are found to have made the mud of the bottom of the seas 

 referred to. It is a grayish mud, tinged with green, and so light, that 

 the plummet was found to have sunk three feet into it, almost as if it 

 had been water. This mud, under the microscope, was found to be 

 entirely shoals of shells, and the beautiful snow-white forms which 

 they individually represent are distinctly shown. 



Between TeneriflTe and St. Thomas, the Challenger found two deep 

 valleys at the bottom of the sea, from which it drew up red mud from a 

 great depth. This mud showed no shells at all, but Dr. Thompson, the 

 chemist on the ship, found that, though the shells were absent, the 

 chemical ingredients of the mud, which was simple clay, were the 

 same as the mud taken at less depths. Thus, it was proved that the 

 red clay was the ashes of the plants and animals which had been dis- 

 solved at that great depth. In the opinion of Dr. Thompson, this was 

 due to the fact, as shown by observation, that the deeper strata are 

 very rich in carbonic acid, this, forming more than one third of the 

 gaseous component of the water. This composition, together with the 

 very great pressure exercised, causes a rapid solution of carbonate (jf 

 lime, leaving only the other constituents. Therefore, what Ehrenberg 



