90 GENERAL HISTORY OF 



observes, that from 1790 to 1819, there fell of the latter, stones 

 whose weight amounted to 600 cwt., while in a single dust shower at 

 Lyons in 1846, the material weighed full 7200 cwt. Other storms 

 of dust in Italy, at Cape Verd, and other places, have even exceeded 

 that at Lyons, in the amount of solid matter which fell on the earth, 

 and Ehrenberg asks, how many millions of tons weight of micro- 

 scopic organisms have reached the earth since the time of Homer. 

 He adds, " I cannot longer doubt, that there are relations according 

 to which living organisms may develope theniselves in the air." 



He supposes the atmospheric dust cloud region is of vast extent, 

 and at a height of more than 14000 feet. Ehrenberg considers these 

 phenomena cannot be traced to mineral substances from the earth, nor 

 to revolving masses of dust material in space, nor simply to atmo- 

 spherical currents, but to some general law connected with the 

 earth's atmosphere, according to which, there is a self-development 

 within it of li\-ing organisms. 



The following, are selected from the showers of Infusorial organ- 

 isms recorded ; — 



1. In the Atlantic, latitude ll"" 43' K. and longitude 26* W. 

 about 500 miles from the coast of Africa, the dust, as it fell, wa» 

 eoUected by Mr. Darwin, fixim the deck of the ship. The wind at 

 the time being from the coast. It resembled ashes. On examina- 

 tion, one-sixth of it consisted of the silicious fresh water Infusoria 

 and Phytolites — 18 species of each. Most of them were European, 

 and none exclusively African. Also a South American species, 

 Surirella Peruviana, and the Himantidium papilio. The inference 

 formed by Ehrenberg is, that this shower came from the upjier 

 regions of the air from South America, othermse those species are 

 yet to be discovered in otlwi^r countries. 



2. Dust from other showers in the Atlantic were collected by the 

 same naturalist, between the years 1834 and 1838. These collec- 

 tions contain 30 additional forms of Infusoria, also the two species 

 above named. Three of the species of Eunotia have only been met 

 with in Senegambia and Guiana, also the South American AmpM- 

 fiiscus obtusus. No species- peculiarly African was foimd in any of 

 the dust. 



S. Dust from Malta, which fell on May 15, 1830, contained 43 



