ALTERATIONS OF THE BOLAR LIGHT. \££ 



of imperfect conductors is to be overcome, the combination 



must be great, but the "size of the plates may be small; but 



it' quantity and intensity Be both required, then a large 



number of lar^e plates will be necessary. For general pur- 4 inches square 



poses, four inches square will be found to be the most con- a . conven »« lit 



venient size. 



Of the two methods usually employed, that of having the Phtesjeined 

 copper and zinc plates joined together only in one point, together in one 

 and movable, is much better thtm the old plan of soldering f eia 5i Cm 

 them together, through the whole surface, and cementing 

 them into the troughs : as, by the new construction, the ap- 

 paratus can be more easily cleaned and repaired, and a dou- 

 ble quantity of surface is obtained. For the partitions in Troughs of 

 the troughs, glass seems the substance best adapted to se- Wedgwood's 

 cure a perfect insulation ; but the best of all, will be troughs 

 made entirely of Wedgwood's ware, an idea, 1 believe,first 

 suggested by Dr. Eabington. 



XL 



Report of a Memoir of Mr. Hassenfratz, respecting the 

 Alterations, that the Light of the Sun undergoes in tra- 

 versing the Atmosphere. By Mr. Hauy*. 



Jl HE class of physical and mathematical sciences having 

 directed Mr. Laplace and me to examine a paper of Mr. 

 Hassenfratz on the changes that the solar light undergoes 

 in passing through the atmosphere, we shall proceed to give 

 an account of it. 



The light of the sun being composed of an infinite imm- Thesun would 

 ber of rays of different tints, the union of which forms always appear 

 white, we should always see it white, if it came to us in the w '. te ' [J u . 



* •* ray?* v/ ere not 



state in which it is emitted from that body. But in passing affected in 

 through the atmosphere it frequently undergoes alterations, [he^atmo^ 

 that change its appearance, so that there are circumstances sphere. 

 \n which it appears to us with its natural whiteness, and 



* Journal de Physique, vol. LXVI, p. £56. 



other* 



