There seems to be a good field before electricians to catch the smoke on the wing and deposit its dust on a large scale. This seems to be a matter beyond our reach at present, except in the scientist's laboratory; but certainly it is a "consummation devoutly to be wished." CHAPTER XXVI RADIATION FROM SNOW One night a most interesting paper by Dr. Aitken, on "Radiation from Snow," was read by Professor Tait to the Fellows of the Royal Society of Edinburgh. I remember that Dr. Alex. Buchan--the greatest meteorologist living--spoke afterwards in the very highest terms of the subject-matter of the paper. This was corroborated by Lord Kelvin, Lord MacLaren, and Professor Chrystal. Dr. Aitken had been testing the radiating powers of different substances. Snow in the shade on a bright day at noon is 7 deg. Fahr. colder than the air that floats upon it, whereas a black surface at the same is only 4 deg. colder. This difference diminishes as the sun gets lower; and at night both radiate almost equally well. I select, among the careful and numerous observations, the notes on January 19, 1886; for I took note of the cold of that day in my diary. It was the coldest day of the whole of that winter. The barometer was 28.8 inches, and the thermometer 4 deg.--that is, 28 deg. of frost. According to Dr. Buchan, that January had only two equal in average cold for fifty years. On January 19, at 10 A.M., when the air was at 20 deg. and the sky clear, a black surface registered 16 deg. and the upper layer of snow 12 deg., showing a difference of 4 deg. when both surfaces were colder than the superincumbent air. It is curious to note that, on February 5 of the same year, at the same hour, when the sky was overcast, the air was at 23 deg., the black surface registered 29 deg., and the snow 25 deg., showing again the difference of 4 deg.; but, in this case, both surfaces were warmer than the air. In both cases the radiation at night was equal. This small absorbing power of snow for heat reflected and radiated from the sky during the day must have a most important effect on the temperature of the air. The temperature of lands when covered with snow must be much lower than when free from it. And, when once a country has become covered with snow, there will be a tendency towards glacial conditions.