560 DEEP-SEA DEPOSITS. 



globules collected .in atmosj)lieric dust arises from the discovery that 

 has beeu made of quite siiuilar globules iu sedimeuts anterior to the 

 existence of man, several of which date even from very remote geolog- 

 ical periods. To limit our exainples, we will mention, according to 

 Messrs. G. Tissandier and Stanilas Meunier,* the abundance of the 

 small bodies in question in the green sand and the clays under the sheet 

 of bubbling water of the artesian wells of Paris. 



This cosmic origin makes it clear how similar dust would abound in 

 regions far removed from any inhabited place. At the summit of the 

 highest mountains, upon Mont Blanc, for example, the melted snow 

 water gives a sediment in Miiich the globules we speak of are not 

 wanting. 



The presence of nickel in certain dust seems to confirm their extra- 

 terrestrial origin. Such was the case with those which Mr. Albert 

 Tissandier collected on the col des Tours at 2,710 meters of altitude, on 

 the occasion of his ascension in 1877. 



From the limited number of falling meteorites, the products of which 

 are collected each year, a very incomplete idea is formed of their fre- 

 quency. The enormous majority necessarily escapes the most eager 

 search even in the midst of the densest populations, either being dis- 

 guised in the vegetation, on account of their usual smallnessof size, or 

 else because they enter the soil. The largest number also fall in unin- 

 habited or savage countries and specially in the basin of the seas. 



It is thus recognized <i iwiori that cosmic dusts must exist not only 

 on the surface of continents, but also on the basin of oceans. 



Without diminishing the incontestable importance of the facts just 

 set forth, there must also be taken into account certain geological 

 plienomena to which the mineral globules may owe their birth. Such 

 is the opening of vertical canals like volcanic chimneys, which under 

 the names of (liatrones traverse the terrestrial crust, the production of 

 which I liave recently realized by the experimental method,! 



The perforation of different rocks, traversed by currents of gas which 

 has at the same time a very strong pressure, a great swiftness, and a 

 high temperature must have produced dusts, the spheroidal grains of 

 which, often hollow, are very abundant. 



CHEMICAL AND MINERALOGICAL PRODU' TIONS FORMED ON THE 

 GREAT OCEAN BOTTOMS. 



We see every day on the continents rocks of very different kinds 

 chemically modified under the mere action of air and water, and tlnis 

 giving birth to new substances. In the same way the deposits formed 

 iu the depths of the sea have not escaped certain chemical actions, in 

 spite of the temperature near zero which reigns there. A state of 



* Comptes Revdus of ihe Academy of Sciences; 1878; vol. lxxxvi, p. 450. 

 iExperiniciits upon the possible effects of subteiTauean gases. Comptes Bendus oj 

 the Academy of Sciences, 1891; vols, cxiand cxil. 



