THE ROCKS OF THE EARTH'S SURFACE SHELL 39 



these deposits are the so-called " ooze," composed of the cal- 

 careous or chitinous parts of algae and of minute animal organisms. 

 The pelagic or surface waters of the ocean are, as it were, a great 

 meadow of these plant forms, upon which the minute Crustacea, 

 such as gldbigerina, foraminifera, and the pteropods, feed in count- 

 less myriads. The hard parts of both plant and animal organisms 

 descend to the bottom and there form the ooze in which are some- 

 times found the ear bones of whales and the teeth of sharks. 



In the deeps of the ocean, none of these vegetable or animal 

 deposits are being laid down, but only the so-called " red clay," 

 which is believed to represent decomposed volcanic material 

 deposited by the winds as fine dust on the surface of the ocean, or 

 the product of submarine volcanic eruption. From the absence 

 of the ooze in these profound depths, the conclusion is forced upon 

 us that the hard parts of the minute organisms are dissolved while 

 falling through three or four miles of the ocean water. 



READING REFERENCES FOR CHAPTER IV 



J. S. DILLER. The Educational Series of Rock Specimens collected and 



distributed by the United States Geological Survey, Bull. 150 



U. S. Geol. Surv., 1898, pp. 1-400. 



L. V. PIRSSON. Rocks and Rock Minerals. Wiley, New York, 1908. 

 SIR JOHN MURRAY. Deep-sea Deposits, Reports of the Challenger 



expedition, Chapter iii. 

 L. W. COLLET. Les depdts marins. Doin, Paris, 1907 (Encyclopedic 



Scientifique). 



