posed to a radiation of 30° of the thermomultiplier, have furnished the following results:
|Order of the screens.||Deviations of the
These transmissions present nothing extraordinary: the quantity of heat which passes through the medium is greater in proportion as the surface is more finely polished, as it happens in respect to light. The only thing to be remarked is, that in the high degrees of polish a slight difference produces a very slight effect. This is evident from the observations made on Nos. 7 and 8.
Similar processes enable us to determine the influence of thickness, which is one of the elements most necessary to be known in the theory of transmission.
Four pieces cut out of a fine mirror were reduced with great nicety to different degrees of thickness in the ratio of 1, 2, 3, 4: particular care was taken to give to their principal surfaces a perfect parallelism, and the highest polish possible. The following are the deviations which they successively produced in the index of the galvanometer under the action of the same radiation, namely 30°:
|Thickness of the screens
|Deviations of the