Page:Philosophical Transactions of the Royal Society A - Volume 184.djvu/21

Rh

It will be seen that on such days the same order of change in the coefficients is to be found.

Other coefficients were obtained on moderately bright days, which are higher than the above for the varying heights of the barometer. These observations are given to show the great variations which may occur owing to atmospheric conditions.

It thus appears that the light acting on platinum paper at any altitude up to those observed can be expressed by = le-H, M.:/80 where h is the height of the barometer and My is the coefficient of absorption. In the case of the most transparent atmosphere My = ·453 at a barometer of 30 inches in height. Therefore I'=le-000503812 The coefficient for the visual absorption is ·341'. A = Ae-000171672 where A and A' are the original and transmitted lights.

We thus arrive at the following results:—