AND ON A SIMPLE PHOTOMETER. 367 



Now, let us imagine this stratum to be transferred to the surface of the sun. 

 It would there be spread over 46,275 times less area ; consequently, its thickness 

 would be increased that number of times, and would therefore amount to about 

 1132 inches, or about 94 feet, embracing 138,825 layers of flame, equal in bright- 

 ness to an electric light of the above-mentioned intensity, and it would at its 

 outer surface possess a brilliancy equal to that of the surface of the sun. 



It is evident, however, that there might be a very considerable addition made 

 to the thickness of such a stratum, without affecting, in any appreciable degree, 

 its proportion to the planetary distances. If then, the thickness of the stratum 

 were increased 520 times, making it 49,000 feet, then it might embrace 72,000,000 

 layers, each of them having an individual brilliancy not greater than that of a 

 wax candle. The real thickness of the stratum in which the luminous property 

 of the sun resides, may be very considerably greater than the above estimate, 

 which is somewhat over 9 miles ; and the luminosity of each individual film com- 

 posing the stratum may be very considerably less, without affecting the general 

 result, 



VOL. XXI. PART III. - _ 



O Cr 



