Column II. of the following Table, calculated by Mr. Meech,[43] represents the quantity of heat received from the sun on the 15th of June at every 10° of latitude. To simplify the Table, I have taken 100 as the unit quantity received at the equator on that day instead of the unit adopted by Mr. Meech:—
+-----------+---------+-----------+-------------+ | | I. | II. | III. | | | | | | | |Latitude.| Quantity | June | | | | of heat. | temperature.| +-----------+---------+-----------+-------------+ | | ° | | ° | |Equator | 0 | 100 | 80·0 | | | 10 | 111 | 81·1 | | | 20 | 118 | 81·1 | | | 30 | 123 | 77·3 | | | 40 | 125 | 68·0 | | | 50 | 125 | 58·8 | | | 60 | 123 | 51·4 | | | 70 | 127 | 39·2 | | | 80 | 133 | 30·2 | |North Pole | 90 | 136 | 27·4 | +-----------+---------+-----------+-------------+
The calculations are, of course, made upon the supposition that the quantity of rays cut off in passing through the atmosphere is the same at the poles as at the equator, which, as we know, is not exactly the case. But, notwithstanding the extra loss of solar heat in high latitudes caused by the greater amount of rays that are cut off, still, if the temperature of the arctic summers were at all proportionate to the quantity of heat received from the sun, it ought to be very much higher than it actually is. Column III. represents the actual mean June temperature, according to Prof. Dove, at the corresponding latitudes. A comparison of these two columns will show the very great deficiency of temperature in high latitudes during summer. At the equator, for example, the quantity of heat received is represented by 100 and the temperature 80°; while at the pole the temperature is only 27°·4, although the amount of heat received is 136. This low temperature during summer, from what has been already shown, is due chiefly to the presence of snow and ice. If by some means or other we could remove the snow and ice from the arctic regions, they would then enjoy a temperate, if not a hot, summer. In Greenland, as we have already seen, snow falls even in the very middle of summer, more or less, nine days out of ten; but remove the snow from the northern hemisphere, and a snow-shower in Greenland during summer would be as great a rarity as it would be on the plains of India.