On the other hand, it may be that ranges of mountains covered with perpetual snow, and valleys piled up with huge glacial accumulations, extend all the way to the Pole, and thus give to our globe an arctic ice-cap like that displayed on the planet Mars. This, however, is very improbable, for, if it were the case, we ought to find a circumpolar ice-wall like that of the antarctic regions; the Arctic Ocean beyond the North Cape should be crowded with icebergs instead of being open and iceless all the year round. With such a configuration the ice-wall should reach Spitzbergen and stretch across to Nova Zembla; but, instead of this, we have there such an open stretch of arctic water, that in the summer of 1876 Captain Kjelsen, of Tromsö, sailed in a whaler to lat. 81° 30´ without sighting ice. He was then but 510 geographical miles from the Pole, with open sea right away to his north horizon, and nobody can say how much farther. These problems may all be solved by the proposed expedition. The men are ready and willing; one volunteer has even promised 1000_l._ on condition that he shall be allowed to have a seat in one of the balloons. All that is wanted are the necessary funds, and the amount required is but a small fraction of what is annually expended at our racecourses upon villainous concoctions of carbonic acid and methylated cider bearing the name of “champagne.” Arrangements are being made to start next May, but in the meantime many preliminary experiments are required. One of these, concerning which I have been boring Commander Cheyne and the committee, is a thorough and practical trial of the staying properties of hydrogen gas when confined in given silken or other fabrics saturated with given varnishes. We are still ignorant on this fundamental point. We know something about coal-gas, but little or nothing of the hydrogen, such as may be used in the foregoing expedition. Its exosmosis, as proved by Graham, depends upon its adhesion to the surface of the substance confining it. Every gas has its own speciality in this respect, and a membrane that confines a hydrocarbon like coal-gas may be very unsuitable for pure hydrogen, or _vice versâ_. Hydrogen passes through hard steel, carbonic oxide through red-hot iron plates, and so on with other gases. They are guilty of most improbable proceedings in the matter of penetrating apparently impenetrable substances. The safety of the aeronauts and the success of the aerial exploration primarily depends upon the length of time that the balloons can be kept afloat in the air.