METEOROLOGY. 307 



178. Dr. Maurer contributes to the Archives of Geneva a study upon 

 the theory of the absorption of the soUir rays by the atmosphere. He 

 attempts to compute more accurately the thickness of the stratum 

 traversed by the rays at any altitude; his figures are slightly larger 

 than those of Laplace, but they are still not beyond criticism. {Z. 0. 

 G. M., XIX, p. 203.) 



179. Prof. S. P. Langley, of Allegheny Observatory, has finally pub- 

 lished the full text of his extensive researches into solar radiation and 

 atmospheric absorption as a professional paper of the Signal Service. 

 Preliminary' to this full publication, be has communicated some of his 

 results to the scientific world through the Philosophical Magazine, the 

 Comptes Eendus, and the American Journal of Science ; a Memoir bear- 

 ing on the same subject also appears in volume 2 of the Memoirs of 

 the National Academy of Sciences. In general he finds the following 

 l)oints established : 



1. After the passage of the solar rays through the atmosphere the 

 maximum of heat in the diffraction spectrum lies near the wavelength 

 O.OOOG of a millimeter, and therefore in the orange portion, agreeing 

 with the maximum intensity of light. 



2. Before its passage through the atmosphere the maximum of heat 

 intensity was near the blue. 



3. The red and ultra-red rays, especially the latter, suffer the least ab- 

 sorption by the atmosphere, while the blue and ultra-blue suffer the 

 most. 



4. The energy in the solar rays, before entering the atmosphere, is 

 1.569 times the energy for a vertical sun after passing through ttie at- 

 mosphere, but this latter corresponds to 1.81 calories, wherefore the true 



'solar constant is 2.84 calories, and Langley believes that the correct 

 value may even be 3. {Z. 0. G. M., xviii, ]). 233; and Sifjnal Service 

 Professional Paper No. xiv.) 



180. O. Frolich contributes to the question of the constancy of the 

 solar heat an important series of observations made with apparatus of 

 his own invention, being a modification of the thermopile, with which 

 he conducted his investigations into the temperature of space and of 

 the sky. As a constant source of heat with which to compare the 

 radiation from the sun he used a surface heated to a temperature of 

 lOOo 0. His observations were made in September, 1879, on the sum- 

 mit of the Faulhorn, in Switzerland ; in the winter of 1879-'80, at the 

 Koyal Observatory at Berlin ; then, to the end of 1882, at the villa of 

 G. Hansemann : and in 1883, in a tower at West-end, near Berlin. This 

 constitutes the most extensive series of observations hitheito available, 

 and they have been discussed with great care Among his results we 

 quote the following : 



In a perfectly clear sky the atmosphere absorbs a variable quantity, 

 as shown by the variations in the so-called atmospheric constant, which 

 has the least value on the loth of October and the greatest on the 12th 



