The investigations of the Swedish naturalist in this field are of exceeding interest. His first attempt to obtain meteoric dust was at Stockholm, where, in December, 1871, there was a great fall of snow, the heaviest ever known. On the last days of the storm, after the atmosphere had been presumably purified of extraneous substances, he collected a cubic metre of snow, melted it over a fire, and found that after the water had evaporated a residue of black powder remained, in which were many grains of metallic iron, that were attracted by a magnet. In 1872 his brother made a similar examination of the snow, in a quiet locality near the remote village of Evois, Finland. The snow upon being melted also gave the same black powder and metallic iron. The investigations of Nordenskjöld himself, conducted in Spitzbergen, as previously mentioned, were the most satisfactory. The observations were made in 80° north latitude, and 13° to 150° east longitude, in the layer of snow that covered the ice. An imaginary section was as follows: (1), new fallen snow; (2), a layer of hardened old snow, eight millimetres in thickness; (3), a layer of snow, conglomerated to a crystalline granular mass; and (4), common granular hardened snow. Layer three was full of small black grains, among which were found numerous metallic particles, that were attracted by the magnet, and found to contain iron, cobalt, and possibly nickel also. In his visit to Greenland in 1870, Nordenskjöld found in the dust that lay on the inland ice, grains of metallic iron and cobalt. “The main mass,” he says, “consisted of a crystalline, double refracting silicate, drenched through with an ill-smelling organic substance. The dust was found in large quantities at the bottom of innumerable small holes in the surface of the inland ice. This dust could scarcely be of volcanic origin, because by its crystalline structure it differs completely from the glass dust that is commonly thrown out of volcanoes, and is often carried by the wind to very remote regions; as also from the dust which, in March, 1875, fell at many places in the middle of Scandinavia, and which was proved to have been thrown out by volcanoes in Iceland.” Professor Nordenskjöld’s estimate of the quantity of dust shows that it has been in past ages a not unimportant factor, perhaps, in its addition to the crust. He says, “I estimate the quantity of the dust that was found on the ice north of Spitzbergen, at from .01 to 1 milligram per square metre; and probably the whole fall of dust for the year far exceeded the latter figure. But a milligram on every square metre of the surface of the earth amounts for the globe to five hundred million kilograms (say half a million tons). Such a mass, collected year by year during the geological ages, of a duration probably incomprehensible by us, becomes a consideration too important to be neglected, when the fundamental facts of the geological history of our planet are enumerated.