REPORT ON THE DEEP-SEA DEPOSITS. 
XXVll 
The dredgings and soundings along the coast of America, taken by the U.S. Coast 
Survey in 1867, were subsequently examined by Pourtales. He found among the 
deposits two well-marked varieties, siliceous and calcareous ; the siliceous deposits 
extended along the coast as far as Cape Florida. The calcareous deposits are divided 
into Coral and Foraminiferous formations, the latter found in the greatest depths. He 
also distinguished a muddy deposit, which he considered quite subordinate and related to 
the Tertiary formations.^ 
Pourtales also gives a description of the different stages in the formation of glauconite. 
He says : — “We find, side by side, the tests perfectly fresh, others still entire, but filled 
with a rusty-coloured mass, which permeates the finest canals of the shells like an 
injection. In others, again, the shell is partly broken away, and the filling is turning 
greenish ; and finally we find the casts without trace of shell, sometimes perfectly 
reproducing the internal form of the chambers ; sometimes, particularly in the larger 
ones, cracks of the surface or conglomeration with other grains obliterates all the 
characters. They even coalesce into pebbles, in which the casts can only be recognised . 
after grinding and polishing.” ^ Pourtales observes that these glauconitic grains are 
deposited in depths of 50 to 100 fathoms near the coasts of Georgia and South Carolina, 
L. Agassiz discussed the results of Pourtales’ observations, and states that what he 
had seen of deep-sea deposits seemed to indicate that no recent or ancient formation ever 
occurred in very deep water. He concludes that the present continental areas within 
the 200-fathom line, as well as the oceans, have preserved their outlines and positions 
from the earliest times.^ 
In the Eeports of Carpenter, Wyville Thomson, and Gwyn Jeffreys, on the cruises of 
H.M.SS. “ Lightning,” “ Porcupine,” and “ Shearwater,”* there are many references to the 
marine deposits collected in the sounding tube and dredges. A comparison is especially 
drawn between the White Chalk and the Atlantic mud or ooze ; in the earlier Eeports it 
was suggested that “ we are still living in the Cretaceous epoch,” and in later ones that 
the Atlantic mud “ might have been accumulating continuously from the Cretaceous or 
even earlier periods to the present day.”® 
In 1871 Delesse published his work “Lithologie du Fond des Mers,” treating more 
particularly of coast sediments from the seas of France ; it forms an important contribu- 
tion to our knowledge of marine deposits, and contains lithological charts founded upon 
the official charts published by the European and American Governments. 
The Challenger Expedition left England in 1872, and during the cruise, which lasted 
nearly three and a half years, many preliminary notices were published by Wyville 
1 E«port of tlie Superintendent of the United States Coast Survey for 1869, pp. 220-225, Washington, 1872. 
^ Loc. cit., p. 224. 
^ Bull. Mus. Comp. Zcol., vol. i. pp. 368, 369, 1869. 
^ From 1868 to 1870 ; published in Proc. Boy. Soc. 
® Thomson, The Depths of the Sea, p. 470, London, 1874. 
