6o ESSAYS AND OBSERVATIONS 



ance of coloured bodies ? Further, are not 

 the intervals of the 6ts, in rays of any one 

 colour, the fame in the fame medium^ from 

 whatever luminous body they are emitted ? 

 For, if thefe intervals were different, would 

 there not be changes in the colours of bodies 

 not to be accounted for by the compofitions of 

 the lights with which they are illuminated* ? 

 'QuER. II, Do not all luminous bodies, 

 the moft languid as well as moft bright, emit 

 their lights of any one colour with one de- 

 terminate velocity ; lince it is found by ex- 

 perience that they are all equally refraded by 

 the fame medium ? And therefore, does not 

 the different fplendor of luminous bodies 

 proceed wholly from the different denfity of 

 their light at equal diftances ? And is not 

 this confirmed by the equality of Bradley^ 

 aberration of light in fixed ftars of all mag- 

 nitudes -f- ? If this be fo, the comparative 

 flrength of different lights, fuch as of the 

 fun, moon, a candle, &c. may be eafily 

 cftimated by finding the greateff diftances to 

 which the fame opaque body is vifible when 

 illuminated by each of them, or the limits be- 

 yond 



» See Art. 



+ i^aro^j's Abridg. of- tranfaft. voj. i, p. 15S. 



