A~]'l PHILOSOPHICAL TRANSACTIONS. [ANNO 1 784. 



the sun exceeds that of a wax candle in no less a proportion than that of 8000 

 to 1. If therefore the brightness of any of the fixed stars should not exceed that 

 of our common candles, which, as being something less luminous than wax, we 

 will suppose in round numbers to be only one 10000th part as bright as the sun, 

 such a star would not be visible at more than an 100th part of the distance, at 

 which it would be visible, if it was as bright as the sun. Now because the sun 

 would still appear, I apprehend, as luminous, as the star Sirius, when removed 

 to 400000 times his present distance, such a body, if no brighter than our 

 common candles, would only appear equally luminous with that star at 4000 

 times the distance of the sun, and we might then begin to be able, with the best 

 telescopes, to distinguish some sensible apparent diameter of it ; but the appa- 

 rent diameters of the stars of the less magnitudes would still be too small to be 

 distinguished even with our best telescopes, unless they were yet a good deal less 

 luminous, which may possibly however be the case with some of them ; for, 

 though we have indeed very slight grounds to go upon with regard to;the specific 

 brightness of the fixed stars compared with that of the sun at present, and can 

 therefore only form very uncertain and random conjectures concerning it, yet 

 from the infinite variety which we find in the works of the creation, it is not 

 unreasonable to suspect, that very possibly some of the fixed stars may have so 

 little natural brightness in proportion to their magnitude, as to admit of their 

 diameters having some sensible apparent size, when they shall come to be more 

 carefully examined, and with larger and better telescopes than have been hitherto 

 in common use. 



26. With regard to the sun, we know that his whole surface is extremely lu- 

 minous, a very small and temporary interruption sometimes from a few spots 

 only excepted. This universal and excessive brightness of the whole surface is 

 probably owing to an atmosphere, which being luminous throughout, and in 

 some measure also transparent, the light, proceeding from a considerable depth 

 of it, all arrives at the eye ; in the same manner as the light of a great number 

 of candles would do, if they were placed one behind another, and their flames 

 were sufficiently transparent to permit the light of the more distant ones to pass 

 through those that were nearer, without any interruption. 



27. How far the same constitution may take place in the fixed stars we do not 

 know ; probably however it may do so in many ; but there are some appearances 

 with regard to a few of them, which seem to make it probable, that it does not do 

 so universally. Now, if I am right in supposing the light of the sun to proceed 

 from a luminous atmosphere, which must necessarily diffuse itself equally over 

 the whole surface, and I think there can be very little doubt that this is really 

 the case, this constitution cannot well take place in those stars, which are in 

 some degree periodically more or less luminous, such as that in Collo Ceti, &c. 



