STUDYING THE SUN'S HEAT ON MOUNTAIN 

 PEAKS IN DESERT LANDS. 



By C. G. Abbot. 



[With 7 plates.] 



As a little boy it used to please me greatly to see the potatoes in the 

 cellar toward spring begin to stretch out long sprouts which had to be 

 rubbed off from time to time. Sometimes one of the potatoes would 

 fall through some crack where it became inaccessible, and its sprouts 

 would grow and grow, sometimes a yard or more, till they came to a 

 little streak of light, always white until the light was reached, but then 

 tending toward green. Again it was a pleasure at the time, and is now 

 a greater pleasure, to look back upon the march of the seasons with the 

 northward and southward excursions of the sun, which changed the 

 New England landscape by a gradual progress from the glories of 

 winter to the beauties and f ruitfulness of spring and autumn. 



In a world where the very life of all the plant kingdom depends 

 upon sunlight, and where the existence of the temperature fit for 

 all life of the animal kingdom depends upon the sun's rays, it may 

 seem an extraordinary statement that until the beginning of the 

 twentieth century no exact measurements of the intensity of the solar 

 radiation on which all things depend had ever been obtained. Some- 

 times one hears the inquiry as to whether the sun's beams are gradu- 

 ally losing their strength and the sun declining toward the condition 

 of a cold body devoid of life-giving energy. It is impossible to answer 

 this question other than to refer to the fact that the crops which were 

 raised in Egypt and Syria in the most ancient recorded times were 

 substantially identical with those that are raised there now, so at least 

 the decline of the sun's radiation has been very little in the last 6,000 

 years. The ancients, although having much astronomical knowledge, 

 never measured, so far as we know, the intensity of the sun's radiation, 

 so that there are no accurate measurements to fall back upon in order 

 to answer this question. 



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