100 
THE VOYAGE OF H.M.S. CHALLENGER. 
continents have always been areas of gradual upheaval, with weak oscillations, while 
the oceans have always been areas of subsidence. Geologists, he says, have often had 
recourse to the hypothesis of marine currents to explain the presence of incoherent 
matters scattered over the sea-bottom, but lie sought in vain in the trough of the Gulf 
Stream for traces of the characteristic mud thrown out by the Amazon, which discolours 
the sea for a long distance seaward. It has often been supposed that the absence 
of fossils denotes a deep sea, but, he remarks, we now know that organisms exist 
even at the greatest depths. Taken in its ensemble, the basin of the Gulf Stream, 
between Cuba and Florida and further north and east, with its very abrupt slopes, 
presents features of configuration differing widely from continental areas of like extent. 
Speaking of the formation of the rocks of the Keyg, especially the oolitic rocks, he con- 
cludes that no rock of the Jurassic formation could have been built up of the materials 
found in the deepest parts of the Atlantic basin ; the vast area occupied by the Keys, 
the reefs of Florida, and the inclined coralline plateau on the American edge of the Gulf 
Stream basin, may be compared with the Jurassic formations of the European and 
Asiatic continents, but their stratigraphic relations show that, during the geological 
middle ages, the Jurassic rocks were formed on the submarine border of a growing 
continent, just as the Pourtales Plateau forms to-day the southern border of North 
America. Returning to the idea of the permanence of continents and ocean basins, he 
concludes by saying : “ If this view is correct, it naturally follows that the main outlines 
and circumscription of the continents and of the oceans must have been determined at 
the very beginning of the formation of inequalities upon the earth’s surface, and remained 
essentially the same through all geological ages, varying only as to their relative height 
and depth, as well as to their respective extension.” 1 
Dr r«>t h Charts In 1871 Deles3e published his work on the lithology of the bottom of the sea, 2 em- 
th® results of long, laborious, and methodical researches, dealing more especially 
f ‘ the Bottom of with the coast sediments of the seas of France. He takes account of the agents assisting 
' u the formation of these deposits, and indicates the samples collected up to that time 
by the hydrographic offices of various countries. His charts are founded upon the charts 
published by the maritime nations of Europe and America, and where the soundings are 
sufficiently numerous he represents the contours of the bottom by curves ; he also 
represent - the orography of the bottom corresponding to the orography of the neighbour- 
ing land, and indicates the limits of the hydrographic basins, the annual rainfall, and 
indeed nil the data bearing directly on the formation of marine deposits, such as currents, 
tide-, prevailing direction of the winds, &c. He divides recent deposits into sand, 
gravel, gravelly sand, boulders, ooze, clay or argillite, slimy sand, sandy mud, gravelly 
mud, e deareous ooze, and coralline ground. In addition to the deposits of the coasts of 
• Ibid., p. 377. 
M. Delesse, Litliologie du fond des mere, with folio atlas, Paris 1871. 
