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THE NATIONAL GEOGRAPHIC MAGAZINE 



The difference between the heat out- 

 side the earth's atmosphere and the sum 

 of the various parts of it indicated above 

 is 0.280 calory per sq. cm. per minute, 

 and this we may suppose represents ap- 

 proximately the loss of heat by reflection 

 from the atmosphere to space in the 

 summer of 1912. 



In former years similar experiments 

 to these have been made at Mount Wil- 

 son and Mount Whitney, and it was 

 found in each case that the sum of the 

 radiation: (A) of the direct solar beam, 

 (B) from the sky, and (C) lost by the 

 absorption in the atmosphere, lacked 

 less than 0.05 calory of the total heat- 

 ing effect outside the atmosphere. 



I am of the opinion that the difference 

 between these results of 1912 at Bassour 

 and those of earlier years at Mount Wil- 

 son and Mount Whitney (or about 0.20 

 calory) represents approximately the 

 radiation reflected away to space by the 

 volcanic dust of 1912, or, in other words, 

 the loss of heat available to warm the 

 earth, which we must attribute to the 

 great haziness which prevailed in 1912. 

 The difference is about 10 per cent of the 

 whole intensity of the sun's radiation 

 outside the atmosphere. Hence I con- 

 clude that the dust of Katrnai diminished 

 the heat available to warm the earth in 

 the north temperate zone by about ten 

 per cent during the summer of IQ12. 



In accordance with the laws of heat 

 and radiation, this might produce a fall 

 of 7° centigrade in the temperature of 

 the earth as a whole, if it was effective 

 for a long enough period of time, pro- 

 vided that there were no counteracting 

 influences, such as altered cloudiness or 

 decreased nocturnal earth radiation, 

 brought about at the same time with, 

 and perhaps by reason of, the increased 

 haziness of the atmosphere.* 



* The results here given on the combined 

 brightness of the sun and the sky must as yet 

 be regarded only as provisional. No experi- 

 ments were made at Bassour on the brightness 

 of the sky prior to the coming on of the haze; 

 hence we shall be obliged to wait until the 

 haze has entirely cleared before we can have 

 measurements strictly representative of the 

 conditions which would prevail there in a clear 

 sky. Dr. Dorno, observing at Davos, in Swit- 

 zerland, does not confirm my conclusion that 

 the total brightness of sun and sky was de- 

 creased by the presence of the haze, although 



world-wide; haze caused by terrific 

 eruptions in japan and iceland 



Having now given estimates of some 

 effects of the great haziness of 1912, we 

 shall next consider whether volcanoes 

 can really produce such world-wide 

 haze. To answer this we have only to 

 go back to the records of times of the 

 greatest volcanic actions of the last 150 

 3rears.* 



In the year 1783 occurred the eruption 

 of Asamayama, Japan, stated to be the 

 most frightful eruption on record. Im- 

 mense rocks were hurled in all direc- 

 tions and towns and villages buried. 

 One stone, said to be 264. X 120 feet, fell 

 into a river, and looked like an island. 



In the same year occurred the (if pos- 

 sible) still more extraordinary eruption 

 of Skaptar Jokull, in Iceland, beginning 

 near the end of May and producing the 

 most violent eruptions on June 8 and 18. 

 Arago records that the dry "fog of 1783 

 commenced about the same day (June 

 18) at places distant from each other, 

 such as Paris and Avignon, Turin and 

 Padua. It extended from the north 

 coast of Africa to Sweden and lasted 

 more than a month. 



The lower air did not seem to be its 

 vehicle, for in some parts the fog came 

 on with a south, in others with a north, 

 wind. Abundant rains and the strongest 

 winds did not dissipate it. In Eanguedoc 

 its density was such that the sun was not 

 visible in the morning up to 17° altitude 

 above the horizon. The rest of the day 

 the sun was red, and could be observed 

 with the unprotected eye. At the time i 

 of new moon the nights were so bright f 

 that the light was compared to that of 

 full moon, even at midnight." 



In 1814 occurred the great eruption of 

 the volcano of Mayon, in the Philippine 

 Islands, and on April 7 to 12, 181 5, the 



he found very strong effects of the haziness 

 in reducing the intensity of direct sun rays, 

 and noted even that the combined brightness 

 of sun and sky in the green had fallen off by 

 7 per cent as compared with that of the com- 

 bined brightness in the red. His measure- 

 ments of the combined brightness do not ex- 

 tend to the whole spectrum, so that it is possi- 

 ble that in this fact may lie the explanation of 

 the divergence between his results and mine. 

 * See Report of Krakatoa Committee of 

 Royal Society of Great Britain. 



