On the Power of Glass of Antimony to refect Light. 7 



timony, I noted down (as usual) only to degrees and tenths of 

 degrees ; and where minutes are set down in the Tables other- 

 wise than such even tenths, it has arisen from averages of 

 different trials. 



Having now a regular series of reflections, most pro- 

 bably equally accurate with any which could be obtained by 

 the infinitely more tedious and laborious method of lamps, we 

 may examine the curve which those reflections indicate, and 

 find the equation which will give the intensity of the reflection 

 for glass of antimony at any required incidence. 



Accordingly, taking the abscissa x of rectangular poordi- 

 nates equal to the sine of incidence to radius (r) as 100, which 

 is the number of rays we suppose incident, and the ordinate 

 u, equal to the intensity of the reflection at that incidence, 

 we have the formula I formerly discovered for glass, as fol- 



lows, namely, y = a -\- 



7+6- 



, which is the equation of a 



rectangular hyperbola, becoming similar to d cf'tn the figure, 

 by adopting for the constants a, b, c these values, a = 7"4, 



