The original composition and origin of this substance appears to me exceedingly enigmatical. It was not common carbonate of lime, for the crystals were rhombohedral and did not show the cleavage of calcite. Nor can there be a question of its being arragonite, because this mineral might indeed fall asunder "of itself," but in that case the newly-formed powder ought to be crystalline. Have the crystals originally been a new hydrated carbonate of lime, formed by crystallising out of the sea-water in intense cold, and then losing its water at a temperature of 10 deg. or 20 deg. above the freezing-point? In such a case they ought not to have been found on the surface of the _snow_, but lower down on the surface of the _ice_. Or have they fallen down from the inter-planetary spaces to the surface of the earth, and before crumbling down have had a composition differing from terrestrial substances in the same way as various chemical compounds found in recent times in meteoric stones? The occurrence of the crystals in the uppermost layer of snow and their felling asunder in the air, tell in favour of this view. Unfortunately there is now no possibility of settling these questions, but at all events this discovery is a further incitement to those who travel in the High North to collect with extreme care, from snow-fields lying far from the ordinary routes of communication, all foreign substances, though apparently of trifling importance. As this question can be answered with the greatest ease and certainty by investigations in the Polar regions, I shall here, for the guidance of future travellers, enumerate some discoveries of a like nature which have been made by me, or at my instance. 1. In the beginning of December, 1871, there happened at Stockholm an exceedingly heavy fall of snow, perhaps the heaviest which has taken place in the memory of man. Several persons perished in the snow in the immediate neighbourhood of Stockholm. During the last days of the snowfall I had about a cubic metre of snow collected and melted in a vessel. It left a residue of black powder, which contained grains of metallic iron that were attracted by the magnet. 2. In the middle of March, 1872, a similar investigation was made by my brother, KARL NORDENSKIOeLD, in a remote forest settlement, Evois, in Finland. Here, too, was obtained, on the melting of the snow, a small residuum, consisting of a black powder containing metallic iron. [Illustration: SECTION OF THE UPPER PART OF THE SNOW ON A DRIFT-ICE FIELD IN 60 deg. N.L. One-half the natural size. ]