CHAP. IIL. ] TENERIFFE TO SOMBRERO. 215 
Nature of the Bottom. Nature of the Bottom. 
No. of No. of bel 
eed Glob. Ooze. | Red Clay. sion Glob. Ooze. Red Clay. 
1 1890 ee 13 1900 
2 1945 iS Die 14 1950 oS 
4 2220 Sesto 15 ee 2325 
5 2740 16 Severs 2435 
6 2950 17 Sy ialiene 2385 
q 2750 18 Boake 2675 
8 2800 19 Soret 38000 
9 3150 20 Siohenc 2975 
2720 21 eee 38025 
Pana ts 2575 22 1420 
2025 Ae | 23 450 
The nature and origin of this vast deposit of clay are a ques- 
tion 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 globige- 
rina ooze. Several circumstances seemed, however, to nega- 
tive this mode of origin. The formation seemed too uniform ; 
whenever we met with it, it had the same character, and it only 
varied in composition in containing less or more carbonate of 
lime. 
Again, we were gradually becoming more and more con- 
vinced that all the important elements of the globigerina ooze 
lived on the surface; and it seemed evident that, so long as 
the conditions on the surface remained the same, no altera- 
tion of contour at the bottom could possibly prevent its accu- 
mulation; and the surface conditions in the Mid-Atlantic were 
very uniform, a moderate surface current of a very equal tem- 
perature passing continuously over elevations and depressions, 
and everywhere yielding to the tow-net the ooze-forming fo- 
raminifera in the same proportion. The Mid-Atlantic swarms 
