306 SCIENTIFIC RECORD FOR 1881. 



V. — [a) Solar radiation and atmospheric absorption; (6) Tem- 

 perature OF THE AIR, THE WATER, AND THE GROUND. 



173. Hirn proposes au apparatus for determiuiug the total absolute 

 amount of solar heat on the principle of the surface condenser of the 

 steam engine, namely, a saturated vapor contained within a closed re- 

 ceiver h-ds the tension corresponding to that for the lowest temperature 

 of any part of the walls of the receiver. Hirn fills a copper cylinder 

 with bisulphide of carbon, the evaporation of which by solar heat fills 

 a space within which is a cooling surface; the liquid cooled upon this 

 tlows into a receiver and is measured. {Z. 0. G. M., xix, p. 548.) 



174. Prof. Balfour Stewart, secretajy of the committee appointed by 

 the British Association for the Advancement of Science to consider the 

 best methods of recording the direct intensity of solar radiation, re- 

 ported at the Montreal meeting in j884 that the committee has chiefly 

 devoted its attention to the subject of a self-recording actinometer. It 

 was suggested that a modification of Stewart's actinometer might be 

 adapted to self registration by taking for the quantity to be observed, 

 not the rise of temperature of the inclosed thermometev after exposure 

 for a given time, but the excess of its temperature when continuously 

 exposed over the temperature of the envelope. Professor Stokes showed 

 that in such a static method the inclosure should be of such a nature as 

 to change its temperature very slowly, and that the various portions of 

 the interior should be at the same time of the same uniform tempera- 

 ture. The committee therefore proposed to make an inclosure of suc- 

 cessive layers of [)o!ished plates and somenonconductor ; in the center 

 of this is placed a thermometer of green glass with a flattened bulb, on 

 which the sun's light falls continuously, while in the inclosure near by, 

 but unaflected by the direct sunlight, is a second thermometer. 



175. [This proposed arrangement for continuous self-registration ap- 

 parently embodies tliC same principles that are incorporated in Yiolle's 

 absolute actinometer, where the object sought by Professor Stokes's 

 arrangement is perfectlj' attained by using a jacket of circulating cold 

 water.] {Nature, xxx, p. 498.) 



176. J. Ericsson, of New York, describes a motor for utilizing the sun's 

 radiant heat. This device is less expensive than others hitherto de- 

 scribeil, and was able to generate steam enough to work a steam-engine 

 of inch cylinder and 8 inch stroke, under a pressure of 35 pounds per 

 square inch, at the rate of 120 oscillations per minute. He reasserts 

 liis belief that the solar temperature cannot be less than 1,000,000 de- 

 grees Fahrenheit. {Nature, xxix, p. 217.) 



177. J. Ericsson describes some of his results on the heat of the solar 

 rays as determined by a large solar pyrometer. His computed tem- 

 perature of 3,000,000 depends upon the assumed law of radiation, but 

 the apparatus and observations have some good features. {Nature^ xxx, 

 p. 407.) 



