230 W. Halloclc — Very on Atmospheric Radiation. 



Art. XIX. — Very on Atmospheric Radiation;* by William 



Hallock. 



It will i-equire no long consideration to recognize that the ques- 

 tion of atmospheric radiation and absorption is one of funda- 

 mental importance in meteorology, and an equal reflection will 

 convince any physicist of experience of the extreme complexity 

 and difficulty of the search for its answer. 



The problem is naturally divided into two parts: First, the 

 absorption, transmission and re-radiation by the atmosphere of 

 that energy which reaches it direct from the sun ; that is, from a 

 source at a very high temperature. Second, the absorption, 

 transmission and re-radiation of the energy which comes to the 

 atmosphere from terrestial sources ; that is, from a source at 

 medium temperatures. The curve of distribution of energy with 

 reference to wave length is radically different in the case of the 

 two sources, the maximum for the sun lying in much shorter 

 wave lengths than in that for the earth. Here at the outset 

 is the difficult necessity of considering not only the total absorp- 

 tion or radiation, but its distribution as to wave length. Add to this 

 the presence of water vapor in varying relative humidity, and 

 absolute quantity, and of C0 2 , and trouble enough is at once 

 apparent. 



Such a research as this is one properly suited to the resources 

 of a Government Bureau, where a long series of exhaustive inves- 

 tigations may be carried on uninterruptedly by a competent 

 physicist, with liberal provision for all money needed for expen- 

 sive apparatus. In the present case the physicist alone with his 

 zeal, and but little money, seems to have been relied upon to 

 solve the riddle. 



Prof. Very has carried out, with much skill and industry, a 

 highly laborious piece of experimental work, and this, with his 

 theoretical discussions, certainly constitute a most valuable con- 

 tribution to this important subject. At the same time, no one 

 better than he, can realize the still outstanding doubts which 

 cluster about the subject, and which leave the final solution of 

 the problem still indefinite. 



Naturally the bolometer was chosen as the measuring instru- 

 ment, since Prof. Very had already had such valuable experience 

 with it. The Boys radio-micrometer or the Nichols radiometer 

 would have been more sensitive, but too often added delicacy is 

 purchased at the expense of serious disturbances and errors. 



In "Method A," fig. 1, two masses of air at different tem- 

 peratures, confined in long tubes with open ends, were alter- 

 nately interposed between a concave mirror and the bolometer 



* Atmospheric Radiation: a Research conducted at the Allegheny Observatory 

 and at Providence, R. I. : submitted to Willis L. Moore, Chief U. S. Weather 

 Bureau, by Frank W. Yery. Pp. 134, 4to, Washington. 1900— Bulletin G, 

 Weather Bureau, No. 221 (U. S. Dept. of Agriculture). 



