DIA TOMS. 419 



The diatoms are placed on the plate by the aid of an ingenious device called 

 a mechanical finger, by means of which the shells can be picked up singly and 

 given the desired position. Mailer's Typenplatte No. i has twenty-four lines in 

 each of four groups, comprising about 500 individuals of 395 distinct species and 

 17 genera. The cost, with printed. catalogue, is forty dollars. 



Some microscopists are so fond of the study of these minute forms that they 

 scarcely do any other work than to observe, collect, classify, and describe them. 



When it is stated that the names of more than 4,000 distinct species of dia- 

 toms are given in a catalogue published by Frederic Habirshaw, of New York,, 

 each of which has some feature by which it may be distinguished, that this ■ vast 

 kingdom, so to speak, is invisible to the human eye, or nearly so, that when 

 highly magnified many of the species are extremely beautiful, and all of them in- 

 teresting, it is easy to understand why so much interest is taken in them the wide 

 world over, and why every new discovery is heralded, and calls for samples come 

 from the whole scientific world. 



It is an established fact, strange as it may seem, that some of the greatest 

 mountain chains, such as the Andes, and the very soil beneath our feet are 

 chiefly composed of the remains of animalcules, invisible to the eye; that is to 

 say, the matter has been used by animated beings, and returned again to the 

 mineral kingdom, retaining the form which it assumed while a part of their mi- 

 nute bodies. Byron has written with more truth than he probably realized that 

 "The dust we tread upon was once alive," and the remark of Dr. Bucklan.d is 

 often quoted: ''The remains of these minute animals have added more to the 

 mass of minerals which compose the exterior crust of the globe than the bones 

 of the elephants, hippopotami, and whales." 



In the tertiary age, beds of diatomaceous or infusorial earth were deposited, 

 consisting almost wholly of these microscopic organisms. The extent of some of 

 these deposits is almost incredible, and is regarded as an evidence of the great 

 age of the world. The Bohemian deposit in Europe is fourteen feet thick, and, 

 by the estimation of Ehrenberg, contains 40,000,000,000 diatoms to the cubic 

 inch. 



Darwin observed in Patagonia, along the coast for hundreds of miles in ex- 

 tent, a bed of tertiary sedimentary formation, 800 feet in thickness, overlaid by a 

 stratum of diatomaceous earth. At Bilin, in Austria, a bed of infusorial earth, 

 fourteen feet thick, occurs.' One merchant sells annually many hundred tons of 

 it. The Be7'gmehl, or mountain meal, of Lapland and Norway, is from beds 

 thirty feet in thickness. It must be remembered that these deposits extend over 

 many thousands of square miles. Notwithstanding the astonishing fact that vast 

 areas of the earth's surface are built of these minute forms, the true nature of 

 these deposits was not known until 1837, when Ehrenberg pubUshed his celebrat- 

 ed work on that subject. The same deposition is taking place at the present 

 time. In certain lakes in the United States and elsewhere, deposits several inches 

 in thickness accumulate, composed wholly of the remains of recent diatoms. 

 When thoroughly dried a chalky powder is obtained, which, under the micro- 



