PROFESSOR MILLER, ON SPURIOUS RAINBOWS. 



281 



(B) 



Secondary bow, seen through red glass, for which it has been assumed 

 that « = 1.3318, and .-. tt + 2 ^ - 6 v// = 50°.34'. Diameter of the cylinder 

 of water = 0.0206 inch. 



In a third series of observations, the Sun's light, after being trans- 

 mitted through a vertical slit 0.25 inch wide, was received upon a prism 

 distant about 24 feet, having its edge vertical. A second slit also 0.25 

 inch wide being placed immediately behind the prism, a tolerably pure 

 spectrum was formed. The stream of water was then placed at the dis- 

 tance of about 18 feet from the prism, nearly in the brightest part of 

 the spectrum : and the index of refraction of the rays that fell upon 

 the stream, determined in the same manner as that of the light trans- 

 mitted through the red glass. 



