giving a total of 1,900 miles of red clay to 720 miles of Globigerina ooze.

“The nature and origin of this vast deposit of clay is a question of the very greatest interest; and although I think there can be no doubt that it is in the main solved, yet some matters of detail are still involved in difficulty.  My first impression was that it might be the most minutely divided material, the ultimate sediment produced by the disintegration of the land, by rivers and by the action of the sea on exposed coasts, and held in suspension and distributed by ocean currents, and only making itself manifest in places unoccupied by the Globigerina ooze.  Several circumstances seemed, however, to negative this mode of origin.  The formation seemed too uniform:  wherever we met with it, it had the same character, and it only varied in composition in containing less or more carbonate of lime.

“Again, the were gradually becoming more and more convinced that all the important elements of the Globigerina ooze lived on the surface, and it seemed evident that, so long as the condition on the surface remained the same, no alteration of contour at the bottom could possibly prevent its accumulation; and the surface conditions in the Mid-Atlantic were very uniform, a moderate current of a very equal temperature passing continuously over elevations and depressions, and everywhere yielding to the tow-net the ooze-forming Foraminifera in the same proportion.  The Mid-Atlantic swarms with pelagic Mollusca, and, in moderate depths, the shells of these are constantly mixed with the Globigerina ooze, sometimes in number sufficient to make up a considerable portion of its bulk.  It is clear that these shells must fall in equal numbers upon the red clay, but scarcely a trace of one of them is ever brought up by the dredge on the red clay area.  It might be possible to explain the absence of shell-secreting animals living on the bottom, on the supposition that the nature of the deposit was injurious to them; but then the idea of a current sufficiently strong to sweep them away is negatived by the extreme fineness of the sediment which is being laid down; the absence of surface shells appears to be intelligible only on the supposition that they are in some way removed.

“We conclude, therefore, that the ‘red clay’ is not an additional substance introduced from without, and occupying certain depressed regions on account of some law regulating its deposition, but that it is produced by the removal, by some means or other, over these areas, of the carbonate of lime, which forms probably about 98 per cent. of the material of the Globigerina ooze.  We can trace, indeed, every successive stage in the removal of the carbonate of lime in descending the slope of the ridge or plateau where the Globigerina ooze is forming, to the region of the clay.  We find, first, that the shells of pteropods and other surface Mollusca