PROF. EHHENBERG ON FOSSIL INFUSORIA. 407 



infusoria, which serve also for moulds in founderies. These animals 

 which are so useful after death, and form entire rocks, have at present 

 a more special interest in their individuality. The size of a single one of 

 these infusoria, which form the Polirschiefer, amounts upon an average 

 and in the greater part to ^^ of a line, which equals -g^ of the thickness 

 of a human hair, reckoning its average size at ^j^ of a line. The glo- 

 bule of the human blood, considered at 3^, is not much smaller. The 

 blood globules of a frog are twice as large as one of these animalcules. 

 As the Polirschiefer of Bilin is slaty, but without cavities, these animal- 

 cules lie closely compressed. In round numbers, about twenty-three mil- 

 lions of animals would make up a cubic line, and would in fact be con- 

 tained in it. There are 1728 cubic lines in a cubic inch, and therefore a 

 cubic inch would contain on an average about 41,000 millions of these 

 animals. On weighing a cubic inch of this mass, I found it to be about 

 220 grains. Of the 41,000 millions of animals, 187 millions go to a 

 grain, or the siliceous shield of each animalcule weighs about the ywt 

 millionth part of a grain. 



The animalcules of the Raseneisen are only yuoo ^^^^ ^^ diameter, 

 or the 2V part of the thickness of a human hair, ^ of the diameter of a 

 globule of the human blood, -^ of the blood globule of a frog. A cubic line 

 of such animal iron-ochre would thus, in the same relation, contain one 

 thousand millions, one cubic inch one billion, and one cube of nine feet 

 diameter one drillion, of living beings. If we suppose only one fourth 

 of this multitude to be really present, and take no notice of the other 

 three fourths, there yet remain such enormous numbers as to merit the 

 greatest attention. 



Further Notices of Fossil Infusoria ; by Prof. Ehrenberg. 



From Poggendorff's Annalen der Physik und Chemie, vol. xxxviii. No. 6, 

 p. 4.i5, 1836. 



At has been announced as a well-ascertained fact, that the Polir- 

 schiefer of Bilin in Bohemia, which is a member of the tertiary forma- 

 tion, consists almost entirely of the siliceous shields of Gaillonella 

 distans and other infusoria, without any foreign cement. The recent 

 Kieselguhr and the Bergmehl from San Fiore, which are of less geolo- 

 gical interest indeed, consisting of larger infusoria shells, are better 

 adapted than the Polirschiefer (whose minute animalcules require a high 

 and clear magnifying power) to make these organic relations more ap- 

 parent and convincing. The kind exertions and reports of M. Alexander 



