Some Microscopic Builders. 



inspiring do they become ! Who can gaze upon their 

 towering mass unmoved, or help recalling Tennyson's 

 exquisite lines ? 



" There rolls the deep where grew the tree. 

 O earth, what changes hast thou seen ! 

 There, where the long street roars, hath been 

 The stillness of the central sea." 



Living in the sea throughout untold ages, the Fora- 

 minifera have had, and probably still take, the largest share 

 of any forms of animal life in building up and main- 

 taining the solid calcareous portion of the earth's crust, 

 by separating from its solution in sea water the car- 

 bonate of lime continually brought down by rivers from 

 the land. Vast deposits of Foraminifera exist, and may 

 be said to spread over thousands of square miles of the 

 earth's surface. Nummulitic limestone, which is com- 

 posed of disc-shaped Foraminifera called Nummulites, 

 held together by a matrix formed of the finely crushed 

 particles of their shells and of other small Foraminiferae, 

 is known to attain a thickness of several thousand feet. 

 It has a wide geographical distribution, extending 

 through Southern Europe, Greece, Asia Minor, Egypt, 

 Persia, to China and Japan. The Pyrenees, the Car- 

 pathians, Apennines, Alps, and Himalayas, are moun- 

 tain ranges into whose composition nummulitic lime- 

 stone largely enters, while, as already stated, the large 

 deposits of chalk are chiefly composed of the remains 

 of Foraminifera. The vast accumulation of animal 

 remains that this represents staggers the imagination, 

 for it is very difficult to realize the long ages through- 

 out which these remains steadily, unceasingly sank 



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