1086 THE MICROSCOPE IN GEOLOGICAL INVESTIGATION 



the more recent explorations of the deep-sea with the dredge ; which, 

 bringing up half a ton of this deposit at once, has shown that it is 

 not a mere surface-film, but an enormous mass whose thickness cannot 

 be even guessed at. ' Under the microscope.' says Professor "WYville 

 Thomson l of a sample of 1^ cwt. obtained by the dredge from a depth 

 of nearly three miles, ; the surface-layer was found to consist chiefly 



FIG. 810. Microscopic oryanisrns in Levant, mud: A, C, D, silk-ions 

 spiculcs of '/>/////.; B, H. spiculcs of (ifmTni; ]}, calcareous spiculc of 

 < : rxiili/i ; F, G, M, O, portions of calcareous skeleton of l-'.rhinoflermatu \ 

 I, calcareous spicule of i <>!</, mln ; K, L, N, silicions spiculcs of s 

 P, portion of prismatic layer of shell of PiiDia. 



of f'rag- 



of entire shells of Globigerina l>nllt>i(1<>. large and small, an . .., 



incuts of such shells mixed with a quantity of amorphous ndcaivoii> 

 matter in fine particles. ,-i little line sand, and nianv spirule,-. pm-1 ioio 

 of sjiiciiles, and shells of Hml'inlii ,',. .-, |',.\\ spicules of spmiges. and a 



few frustules of diatoms. Below the surface-layer the sediment lie 

 comes gradually more compact . and a slight grey colour, due proliaUv 



i The Depths of the Sea, y. no. s ( .<- also \'n//,if/r ,,i choUnnjo-, di. iii., and 

 ger Reports, e&peci&Ui Deep Sea Deposes (Murraj and 



