SUPPLEMENTARY NOTES. 459 



contain living species of Infusoria, of the same kind that occur 

 in sea water, near Havre in France, and near Wismar on the 

 Bahic; and also that a kind of siliceous paste called Kieselguhr, 

 found in nests of the size of a man's fist or head, in a Peat Bog 

 at Franzenbad, near Eger, consists almost entirely of minute 

 siliceous shields of a species of Navicula, N. viridis, which is 

 now living in fresh-water, near Berlin, and widely diffused else- 

 where. The remains of Infusoria also almost entirely compose the 

 Kieselguhr of the Isle of France, and a similar substance called 

 Bergmehl, from San Fiore, in Tuscany. Nine existing species 

 have been recognised in the Kieselguhr of Franzenbad; in that 

 of the Isle of France five species; in the Bregmehl of San Fiore 

 nineteen species; in the Polierschiefer of Bilin four species. In 

 each of these cases, the greater number of the species are the 

 same that now live in stagnant fresh-water; some inhabit saline 

 mineral waters, and a few live in the sea. The total number of 

 fossil species observed is twenty-eight, fourteen of which agree 

 with living fresh-water species of Infusoria, and five with living 

 marine species. The other nine probably belong to living species 

 not yet discovered. In each of these four localities one species 

 preponderates largely over the rest, and in no two cases is it the 

 same species. The Polierschiefer of Bilin occupies a surface of 

 great extent, probably the site of an ancient lake, and forms 

 slaty strata of fourteen feet iu thickness, consisting almost entirely 

 of an aggregation of the siliceous shields of Gaillondla Distans. 

 The size of one of these is about ^\j of a line which is about i of 

 the thickness of a human hair, and nearly of the size of a globule 

 of the human blood; about twenty-three millions of animals are 

 contained in a cubic line of the Polierschiefer, and 41,000 millions 

 in a cubic inch; a cubic inch of Polierschiefer, weighs 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 jI^ mil- 

 lionth part of a grain. Siliceous remains of Infusoria have recendv 

 been found also in the Polierschiefer of Planitz and Cassel. 



M. de Humboldt has recently communicated to the Academy 

 of sciences at Paris (February 20, 1837,) a letter from Professor 

 Retzius of Stockholm, in which he informs Ehrenberg that a sub- 

 stance called Bergmehl, {Farine de monlagne,) analyzed and 



