Origin of Flint. 171 



proved of chalk, may now be regarded as true of common clay, viz.: 

 that it is the ashes of former organizations of minute life. 



Professor Huxley showed the important bearing of these discoveries 

 on the geological construction of the earth. And he further states that, 

 supposing we had a globe covered with water, wdth no dry land at all, 

 there could be uo wear and tear of coasts, no denudations, and no depos- 

 it of sedimentary rocks. The sea surrounding the North and South 

 poles Avould then be covered with thick layers of these auimalculie, 

 able to draw silica from the water, transmute it into skeletons, and 

 then rain a perpetual shower of such siliceous skeletons to the bottom of 

 the water on the sponge spicules. In the intermediate zones a per- 

 petual shower of calcareous shells would fall in the same way. If the 

 sea bottom were depressed until these were entirely dissolved, or the 

 bottom raised, there would be six different kinds of rocks, such as make 

 the larger part of the earth, that would be attril)uted to the work of 

 these infinitesimal builders alone. These conclusions of Huxley, 

 Newberry, and others, may embrace the correct theory of some 

 siliceous formations. 



The soft mud, found by the Challenger — entire shoaLs of shells, so 

 light that the plummet sunk into it almost as if it had been water — 

 may explain the case referred to by Mantel in his Pictorial Atlas of 

 Fossils, of a stream of liquid flint encasing organic forms. 



But other questions arise, to which I have not found satisfactory 

 answers. If diatoms and animalculae clothe themselves with shields 

 and shells of silica, and finally fall to the bottom of the sea, as uncon- 

 nected particles, how is the additional gelatinous form of siKca gen- 

 erated that gives cohesion and compact structure to these infini- 

 tesimal particles and forms them into solid masses of flint, as we now 

 find it? 



Inasmuch as diatoms have not the power of solidification, cohesion 

 and crystallization, but depend upon some other agent for these condi- 

 tions, may not that other force separate and arrange silica from the 

 water, and precipitate it to the bottom in a condition to produce 

 the uustratified form flint presents to us, without the aid of 

 diatoms or animalculie? And if it Ls conceded that some flints are 

 properly attributed to diatomaceous origin, is it therefore necessary to 

 conclude that they must contribute to the formation of all flint beds 

 that have been discovered ? Some specimens of flint that I have col- 

 lected, and present for your examination, seem to have been formed 

 under a high degree of heat, and are tinged with various colors. 

 Others represent inclosed fossils, mollusks and corals ; others, large and 

 beautiful quartz crystals — transparent, pellucid, ferruginous and drusy, 



