Some further points must be referred to in describing the climatic conditions we experienced. The temperature of the air is doubtless the most important element in the study of climate; but it seems to me that its importance is relatively less in polar regions than in other parts of the globe. In polar latitudes the human organism is chiefly influenced by the absence of the sun during the night of winter. In the summer, on the other hand, the radiant heat of the sun is so strongly concentrated that the temperature of the air scarcely measures the warmth we feel. Further, the action of the solar rays is directly beneficial--the sun strengthens and reanimates. And besides direct insolation, the diffused daylight itself must be considered. One feels quite different under a cloudless vault and under a sky overcast and sombre. The presence or absence of the sun is a much more important matter to us than the state of the thermometer. The wind is another extremely important factor from the physiological point of view. In calm weather a temperature of -20° C. (-4° F.) is quite tolerable, even agreeable if the sun is shining; but with a light breeze one feels the cold at once, and in strong wind it is impossible to remain long in the open air with so low a temperature. It appears to me that humidity plays a quite secondary part in the physiology of the polar climate--at least, at low temperatures; in any case, the humidity of the atmosphere rarely makes itself felt. Some actinometric observations will serve to indicate the intensity of radiant heat. At 2 P. M. on December 30, the temperature of the air being -0.2° C. (31.6° F.), the black-bulb thermometer read 45.1° C. (113.2° F.) in the sun, which explains why in reality the weather felt very warm. The sky was usually overcast, most frequently with a thick layer of stratus, which formed a uniform gray covering, and often persisted for days or even weeks together, with only short breaks. Table IX. shows the state of the sky during each month of the year. The number of days during which the air was not saturated, i.e., on which the hygrometer indicated humidity less than ninety per cent., was, in October, 12; November, 18; December, 22; January, 15; and February, 11. If we include ice-deposits from fog and similar precipitation, we find that snowfall is recorded on 257 days of the year, made up as shown on the first column of Table X. The second column of Table X. shows the number of days on which rain (even a few drops) was recorded. Speaking generally, it may be said that the weather was extremely cloudy, that fogs were frequent, that snow fell on many days, and that the air was saturated nearly the whole time. Table XI. gives particulars with regard to wind force. TABLE I.--MEAN TEMPERATURE.