CHALK UNDER THE MICROSCOPE, 



BY 



CHARLES UPTON. 

 (Read February 14th, 1898.) 



In the early clays of Geology chalk was thought to be a 

 chemical precipitate of carbonate of lime. The micro- 

 scope, however, long ago proved this a mistake : it is 

 almost entirely composed of the remains of minute 

 organisms. 



Of these microzoa the Foraminifera are by far the most 

 important, numerically, in fact it may safely be asserted that 

 our chalk hills are composed of countless millions of the 

 shells of these minute creatures. Ehrenberg endeavoured 

 to form an estimate of the number of their shells in a 

 given mass : he came to the conclusion that a cubic foot 

 of the material contains something like 200 millions. 

 Dr. M. C. Cooke also experimented on several samples : 

 and his conclusions were similar to those of Ehrenberg. 



These investigators only estimated the number of the 

 shells of Foraminifera. I venture to assert that the 

 coccoliths (which are usually taken to be organic bodies) 

 outnumber the Foraminifera by a million to one. The 

 number of Foraminifera which can occupy the space of a 

 drop of water can be counted with some approximation to 

 truth, but the coccoliths which may be taken up in a drop 

 of water are absolutely beyond computation. 



