DEEP-SEA DEPOSITS. 557 



MINERAL SUBSTANCES OF EXTRA-TERRESTRIAL ORIGIN. 



Amoug- tlie substances which have been met in deep-sea deposits, 

 there are some to which it does not seem to the authors possible to 

 attribute a terrestrial origin. On account of their rarity they form 

 only an insignificant portion of the deposits; but the interest they 

 present results from the cosmic origin which we are led to attribute to 

 them. In 1876 Mr. Murray called attention to the singular character 

 of these particles. 



In the midst of the portions which can be extracted by the magnet 

 from certain muds of the abyss black microscopic globules are found, 

 the interior of which consists of metallic iron, and they are covered 

 with a pellicle of magnetic oxide. Traces of cobalt are found in them. 



With these metallic spherules are associated others of the nature of 

 stones; they are brown and of a bronze luster; their diameter aver- 

 ages a half a millimeter and never reaches twice that dimension. 

 Microscopic examination proves that they are not strictly spherical, 

 that their surface instead of being smooth is striated, and that their 

 structure is laminated, taking an eccentric arrangement. These small 

 bodies have then the texture as well as the form of those which 

 abound in stony meteorites and which are characteristic of them. 

 Like the latter, which (lustav Rose has designated under the name of 

 chondrnles, they consist of a silicate belonging to the species enstatite 

 or bronzite. If we assume a meteorite to fall into the sea and become 

 disintegrated, it will be easy for us to understand that such globules 

 would l)e disengaged. 



The metallic globules resemble wholly, in exterior appearance, those 

 which are produced when bits of iron at white heat tiy into the air, 

 such for instance as are prod^^iced by the blow of the lianmier on the 

 anvil. Similar ones are doubtless produced when meteorites throw off 

 sparks in traversing the atmosphere with great rapidity heated to 

 incandescence. Messrs. Murray and Kenard consider themselves, there- 

 fore, authorized to designate the metallic dusts, as well as the stony 

 globules, as cosmic dusts. 



It appears from a great number of examples that the cosmic dusts 

 are found specially in the red clay which occupies the great depths of 

 the Pacitic, for from all continental land. Under these conditions the 

 deposit seems to be of slight thickness and to be effected with extreme 

 slowness. Facts which we witness daily render it easy to understand 

 a cosmic co-operation in the building up of sub-marine deposts. 



Every one has noticed the abundance of dust contained in the atmos- 

 phere that a ray of sun entering a dark room suffices to reveal. Such 

 dust is still more apparent in the layer which settles upon all the objects 

 in an uninhabited place, and even in the open country where the air is 

 comparatively tranquil. It is more and more the unanimous opinion 

 that the atmosphere is no less active a vehicle than water in the forma- 

 tion of sedimentary deposits. 



