FOSSIL INFUSORIA. 431 



violently shaken, in order to break up the minute frag- 

 ments of dirt, and set free the siliceous Diatoms. After 

 shaking, allow the vessel to stand for half an hour or 

 more according to the size and density of the valves : the 

 Diatoms having subdivided, the dirty water is drawn off 

 by a syphon, and fresh water added, and the shaking re- 

 peated. The whole secret depends upon getting rid of 

 the impurities by this violent shaking and washing ; when 

 quite free from all impurities the material may be trans- 

 ferred to a test tube, washed in distilled water, and finally 

 mounted." 1 



Fossil Infusoria. — Startling and almost incredible as the 

 assertion may appear to some, it is none the less a fact, 

 established beyond all question by the aid of the micro- 

 scope, that some of our most gigantic mountain-ranges, 

 such as the mighty Andes, towering into space 25,250 feet 

 above the level of the sea, their base occupying so vast an 

 area of land ; as also our massive limestone rocks, the sand 

 that covers our boundless deserts, and the soil of many of 

 our wide-extended plains; are principally composed of 

 portions of invisible animalcules. And, as Dr. Buckland 

 truly observes : " The remains of such minute animals 

 have added much more to the mass of materials which 

 compose the exterior crust of the globe than the bones of 

 elephants, hippopotami, and whales." 



The stratum of slate, fourteen feet thick, found at Bilin, 

 in Austria, was the first thatwas discovered to consist almost 

 entirely of minute flinty shells. A cubic inch does not 

 weigh quite half an ounce ; and in this bulk it is estimated 

 there are not less than forty thousand millions of indi- 

 vidual organic remains ! This slate, as well as the Tripoli, 

 found in Africa, is ground to a powder, and sold for 

 polishing. The similarity of the formation of each is 

 proved by the microscope ; and their properties being the 

 same, in commerce they both pass under the name of 

 Tripoli : one merchant alone in Berlin disposes annually of 

 many hundred tons weight. The thickness of a single shell 

 is about the sixth of a human hair, and its weight the hun- 



(1) G. Norman, Esq. Micros. Journ. 'vol. iv. p. 238. For other methods of 

 cleaning and preparing Diatoms, see Smith's Synopsis of the British Diato- 

 macece; also Quar. Journ. Micros. Science, vol. vii. p. 107, and vol. i. N. S. 1S61, 

 p. 143. 



