232 W. Hallock — Very on Atmospheric Radiation. 



filled the cross-section of the cylinder. This disk was supposed 

 to remain at the same constant temperature as the gas, a greater 

 or less thickness of which was allowed to radiate out the salt 

 window, according as the disk was near to, or far from, that end 

 of the cylinder. This apparatus, if it had been tight and provided 

 with thoroughly satisfactory means of heating, would have given 

 even better results than it did. By these means the effect of 

 varying temperatures and pressures, relative humidities, and car- 

 bonic acid gas could be determined. 



For example, it was found that for atmospheric pressure and 

 temperatures to 100° C. excess, and a thickness of 141 -8 cm , the 

 ratio of radiation, air : C0 2 = 0-1885/0-1254 = 1-50. The radia- 

 tion from steam was also tried, but the results were inconclusive. 

 " Method D " used the above cylinder to store compressed gases, 

 which after being heated in going through a hot brass tube were 

 caused to pass in front of the bolometer. In this way the rela- 

 tive radiation of air and steam, and clear and smoky air, were 

 studied. It appears that steam under certain conditions radiates 

 at least four times as much as air, and that the presence of con- 

 densed particles of water does not seriously affect the results. 

 A limited series of experiments seemed to show that the presence 

 of fine particles in the air, as in smoke, did not affect its radiation. 



It is manifestly impossible to refer ever so briefly to the mass 

 of details and discussions ; they must be studied in the original. 

 When we consider how much material for study is here presented, 

 and that too many government scientific publications are simply 

 narrations of undigested details, without proper consolidation and 

 abstraction, we must be grateful to Prof. Very for summarizing 

 his work as well as its extreme complexity will admit. Never- 

 theless it will only be practicable to extract here a few sentences : 



"The direct effect of the sun's rays is less on a normal surface 

 in the tropics than in temperate regions, and less at sea level than 

 upon a mountain top, owing to the difference in the aqueous 

 component of the air; and the ability of the solar radiation to 

 maintain a high temperature in the torrid zone or at sea level is 

 due to the accumulation of the thermal energy imparted to the 

 earth's surface by reason of the retention of the escaping radia- 

 tion from that surface by a moist and highly absorbent atmos- 

 phere rather than to the direct power of the sunbeam." (P. 125.) 



" ' Where the land is moist the changes in temperature are less 

 than where it is dry or arid,' but it is the condition of the air and 

 not that of the soil which makes the radiation possible or impos- 

 sible." (P. 127.) 



" Within moderate depths of only a few meters the radiation 

 of dry air, purified from carbon dioxide, increases quite uniformly 

 with the depth; the radiation of a 1-meter layer of purified air 

 at 50° O. and near atmospheric pressure (735 mm ) as compared 

 with one at 0° C, is 0*00068 radim, representing a transformation 

 and transfer of thermal energy of 0-00068 small calories every 

 second through each square centimeter of limiting surface ; the 



