172 SCIENTIFIC ILLUSTRATIONS [Ins 



to Ehrenberg, a cubic inch of the Tripoli sand, which is still in 

 course of formation in the environs of Bilin, in Bohemia, 

 contains eleven millions of the shells of the infusorias which 

 produce this friable substance. The same naturalist states that 

 so great is their power of reproduction, one million of these 

 animalcules are born in ten days of a solitary individual. 

 Bearing these facts in mind, it is not difficult to understand 

 what immense masses of matter must have been deposited by 

 the innumerable generations which have succeeded one another 

 during the long periods of the primitive epochs, and which 

 have covered with accumulated strata, mingled with sedimentary 

 earths, the rocks of igneous origin that formed the first crust of 

 the earth. The fossil debris of such shells as ammonites, nautili, 

 and mummulites, are also found in vast masses, which suffi- 

 ciently indicate the infinite multiplication of life in the dense 

 warm waters of the primeval seas. The illustrious geologist, 

 Dr. Buckland, affirms that the mummulites form a considerable 

 portion of the entire mass of several mountains ; as, for instance, 

 the tertiary calcareous deposits of Verona and Monte Bolca, and 

 the secondary stratified earths in the cretaceous formations of 

 the Alps, the Carpathians, and the Pyrenees. The famous 

 colossal Sphinx, and the hugest of the Egyptian pyramids 

 that which is generally distinguished by the name of Cheops 

 are constructed of a limestone wholly composed of these forami- 

 nifera, which are everywhere widely distributed, and which, by 

 their countless legions, seem to have sought a compensation for 

 their extreme diminutiveness. "The sand of the sea-shore," 

 says Dr. Chenu, "is so filled with foraminifera that one may 

 justly say it is half composed of them. In an ounce of sand in 

 the West Indies were nearly four millions of individuals. The 

 banks formed by these beings impede navigation and render it 

 dangerous, obstruct the gulfs, fill up the harbours, and in con- 

 junction with the madrepores construct those islands which 

 from time to time emerge in the warm regions of the great 

 ocean ; and this role, actually played out to-day by living 

 species, was formerly filled by those which are now found only 

 in a fossil condition. At the epoch of the coal-measures (or 

 carboniferous formation), a single species of Fusulina built up 

 in Russia enormous beds of limestone. The cretaceous deposits 



