272 THREE CRUISES OF THE " BLAKE." 



one hundred fathoms they equal in bulk the grains of sand, and in 

 greater depths they become the chief constituents of the sea bottom, 

 thus gradually passing into and leading us to the true calcareous globi- 

 gerina ooze, and finally disappearing into the red clay formation, in the 

 deeper parts of the Atlantic basin. 



'' In the mud of the ' Block Island soundings,' and of the ' mudholes ' 

 off New York, we find very little besides a few Guttulinae. 



" The' same general distribution pi-e vails all the way to Cape Florida, 

 with few exceptions. Interruptions are rare in this great sandy jjlain 

 of the continental shelf. We find only one or two small rocky patches 

 in the neighborhood of the entrance to New York Bay." 



A triangular area of clayey bottom, of considerable extent, 

 within the hundred-fathom line, extends within the usual limits 

 of the siliceous sands south of Block Island. The northern 

 and southern extensions of this clay deposit, as it gradually 

 fades, or is covered by globigerina ooze, can be traced many 

 miles along the slope of the continental shelf. 



Professor Bailey noticed in the soundings off Montauk Point, 

 in fifty-one fathoms, an exti-aordinary development of forami- 

 nifera, rivalling in abundance, as he says, the vast accumula- 

 tions of analogous forms constituting the marls under the city 

 of Charleston, S. C. In the more southerly soundings of sim- 

 ilar depths, a greater number of globigerinae are found, as well 

 as other genera known to occur in large numbers round the 

 shores of Florida and the West India Islands. Professor Bailey 

 also caUs attention to the fact that these Mexican and Caribbean 

 types are not represented in the chalk, but are very common in 

 the tertiary deposits ; their absence from deep-sea soundings 

 seems to afford additional evidence of the difference in depth 

 at which cretaceous and tertiary beds have been deposited. He 

 further suggests that the immense development of globigerinae 

 and other pelagic foraminifera, forming a perfect milky way 

 along the course of the Gulf Stream, may be due to the high 

 temperature of its surface waters ; and that the deposits under 

 Charleston may have been produced under the similar influence 

 of an ancient Gulf Stream. According to Bailey, the sound- 

 ings around the Atlantic shores and in the course of the Gulf 

 Stream present no analogy to the vast accumulations of infusoria 

 which occur in the miocene marls of Virginia and Maryland. 



