The recent expedition wintered as near as possible to the region of maximum winter cold in the western hemisphere, and pushed their journey northwards athwart the region of maximum summer cold. Along the course pursued by Parry’s route the cold is far less intense, in corresponding latitudes, than along the American route; and cold is the real enemy which bars the way towards the Pole. All the difficulties and dangers of the journey either have their origin (as directly as the ice itself) in the bitter Arctic cold, or are rendered effective and intensified by the cold. The course to be pursued, therefore, is that indicated by the temperature. Where the July isotherms, or lines of equal summer heat, run northwards, a weak place is indicated in the Arctic barrier; where they trend southwards, that barrier is strongest. Now there are two longitudes in which the July Arctic isotherms run far northward of their average latitude. One passes through the Parry Islands, and indicates the sea north-east of Behring’s Straits as a suitable region for attack; the other passes through Spitzbergen, and indicates the course along which Sir E. Parry’s attack was made. The latter is slightly the more promising line of the two, so far as temperature is concerned, the isotherm of 36° Fahrenheit (in July) running here as far north as the 77th parallel, whereas its highest northerly range in the longitude of the Parry Islands is but about 76°. The difference, however, is neither great nor altogether certain; and the fact that Parry found the ice drifting southwards, suggests the possibility that that _may_ be the usual course of oceanic currents in that region. North of the Parry Islands the drift may be northwardly, like that which Payer and Weyprecht experienced to the north of Novaia Zemlia. There is one great attraction for men of science in the route by the Parry Islands. The magnetic pole has almost certainly travelled into that region. Sir J. Ross found it, indeed, to be near Boothia Gulf, far to the east of the Parry Islands, in 1837. But the variations of the needle all over the world since then, indicate unmistakably that the magnetic poles have been travelling round towards the west, and at such a rate that the northern magnetic pole has probably nearly reached by this time the longitude of Behring’s Straits. The determination of the exact present position of the Pole would be a much more important achievement, so far as science is concerned, than a voyage to the pole of rotation.