238 Cincinnati Society of Natural History. 



side, as it wore, of a,n ideal line, the red clay contains more and more 

 of the material of the calcareous ooze, while on the other the ooze is 

 mixed with an increasing proportion of red cla^-. 



" From Teneriflfe to Sombrero, the depth goes on increasing to a dis- 

 tance of 1,150 miles from Teneriffe, when it reaches 3,150 fathoms ; 

 there the clay is pure and smooth, and contains scarcely a trace of 

 lime. From this great depth the bottom gradually rises; and with de- 

 creasing depth the gray color and the calcareous composition of the 

 ooze return. Three soundings in 2,050, 1,900, and 1,950 fathoms, on 

 the 'Dolphin Rise,' gave highly characteristic examples of the glo- 

 bigerina formation. Passing from the middle plateau of the Atlantic 

 into the western trough, with depths a little over 3,000 fathoms, the 

 red clay returned in all its purity; and our last sounding, in 1,420 

 fathoms, before reaching Sombrero, restored the globigerina ooze with 

 its peculiar associated fauna. 



" The distance from Teneriffe to Sombrero is about 2,700 miles. 

 Proceeding from east to west, we have about 80 miles of volcanic mud 

 and sand ; 350 miles of globigerina ooze; 1,050 miles of red clay; and 

 330 miles of globigerina ooze; 850 miles of red cla^'; and 40 miles of 

 globigerina ooze, 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 1 think there can be no doubt 

 that it is in the main solved, yet some matters of detail are still involved 

 in difficult}'. My first impression was, that it might be the most 

 minuteh' divided material, the ultimate sediment, produced by the 

 disintegration of the laud b}^ rivers, and by the action of the sea on 

 exposed coasts, and held in suspension and distributed \)y ocean cur- 

 rents, 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; whenever we 

 met with it, it had the same character, and it only varied in composi- 

 tion in containing less or more carbonate of lime. 



"Again, we 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 conditions on the surface 

 remained the same, no alteration of contour at the bottom could pos- 

 sibly prevent its accumulation; and the surface conditions in the ]Mid- 

 Atlantic were very uniform, a moderate surface current of a ver^y equal 

 temperature passing continuously over elevations and depressions, 

 and everywhere yielding to the tow-net the ooze-forming foraminifera 



