Scientific Intelligence — Meteorology and Geology. 185 



in North America, from New York to Labrador. Similar species 

 of the broad and small many-toothed species of Himaiitidmm and 

 Eunotia only occur on the north coast of Asia, at Senegal in Africa, 

 and in Cayenne in South America. The genus Tetragramma is 

 found only in Libya and in the Ladrone Isles, and the same species 

 occurs at both places. 



" 7. There is distributed over all parts of the eai-th a consider- 

 able number of perfectly identical forms, among which are {Navi- 

 cula), Pinnularia viridis, Himantidum arcus, and Eunotia amphi' 

 oxys. These common forms appear to be the most important in 

 their relations to the economy of nature, 



" 8. The so-called inorganic constituents of tiie body, and shells 

 of animalcules, ai-e chiefly carbon, silica, lime, and iron, with traces 

 of alumina and manganese ; magnesia and other substances are pro- 

 bably only present as mechanical mixtures. 



" 9. The quantity of iron in the minutest organisms is sometimes 

 surprisingly great. It is never united with the lime, but only with 

 the silica, appearing to be rather mechanically than chemically com- 

 bined, and sometimes it seems to exist, in a very peculiar, colourless, 

 and chemically inexplicable state. This mechanical union of iron 

 and silica appear to be chiefly an organic deposition of the metal in 

 closed siliceous cells. 



" 10. In consequence of the uniform and extensive development 

 of minute organic life, it must exert a great and important influence 

 upon other conditions of the surface of the earth, and particularly 

 upon the formation of humus in the valleys of rivers. If the larger 

 organic bodies have direct relations to the condition of the atmosphere, 

 the widely extended and immensely developed minuter forms cannot 

 be without a great influence on those I'elations. 



"11. But the evidence of the influence of microscopic life is not 

 confined to the surface of the earth. The same incomprehensible 

 formation of rocks from the siliceous or calcareous shells of animal- 

 cules which is seen in the chalk formation of Europe, occurs also on 

 a gigantic scale both in the north-east and north-west of Africa 

 (Egypt, Oran). It occurs in the north-west of Asia (Bir Hamam, 

 Ante-Libanus, Libanus), and, according to recent observations, in 

 perhaps still greater development in North America (Mississippi, 

 Missouri, New Jersey). The Jura limestones of Europe also shew 

 generally, and sometimes quite distinctly, an intimate connection with 

 organic life; and the very ancient limestones, and included calce- 

 dony, said to occur directly beneath the coal at Lakes Tula and 

 Onega in Russia, occasionally shew quite distinctly, that microscopic 

 life had as extensive development in that ancient epoch as at any 

 more recent period. Rocky masses of infusoria are presented by 

 the polishing slates of Lucon and Caucasus ; and extensive earthy 

 beds of siliceous infusoria occur, not only in the edible clay of the 

 Amazon, and the very extensive (fifteen to twenty foot thick) infu- 



