THE MICROSCOPE IN GEOLOGY. I J I 



teen fathoms. Whatever be their nature, whether 

 organic or not, it is certain that these bodies abound 

 in extraordinary numbers in chalk and in the ooze at 

 the bottom of the Atlantic, and seem to indicate a 

 similar origin and an essential identity of the chalk 

 with modern deep-sea mud. But besides these cocco- 

 liths and coccospheres so called, chalk contains other 

 bodies round in form, having many chambers in 

 communion with each other, of microscopic size and 

 beautiful construction. These calcareous bodies are 

 of various forms. Professor Huxley very aptly com- 

 pares one of the commonest to a badly-grown rasp- 

 berry, being formed of a number of nearly globular 

 chambers of different sizes congregated together. These 

 bodies have hence been called Globigerincz, and some 

 specimens of chalk consist of little else than Globi- 

 gerinae and the granular bodies already mentioned. 

 What a subject for contemplation have we here ! 

 Immense chalk cliffs extending for hundreds of miles, 

 the vast fabric the work of minute creatures invisible 

 to the naked eye ! In England this chalk formation 

 extends diagonally from Lulworth, in Dorset, to Flam- 

 borough Head, in Yorkshire, a distance of over 280 

 miles "as the crow flies. In some places it is more 

 than a thousand feet thick. Nevertheless, as Pro- 

 fessor Huxley says, "it covers but an insignificant 

 portion of the whole area occupied by the chalk forma- 

 tion of the globe ;" for if all the points at which true 

 chalk occurs were circumscribed, they would lie within 

 an irregular oval about 3,000 miles in long diameter, 

 the area of which would be as great as that of Europe, 

 and would many times exceed that of the largest exist- 

 ing inland sea the Mediterranean ; and all this wide- 

 spread component of the earth's surface consists for 

 the most part of the skeletons or calcareous shells of 

 Globigerinae ! But recent investigations have shown 



