72 L. M. Rutherfurd on Astronomical Observations 
no appreciable dimensions, no light is lost and the spectrum 
Temains uniform an 
It will be easily seen that the lens spoken of is serviceable only 
in observations upon stars, and is of no use in the spectral inves- 
examined as to the zero point, the standard being that the “— 
line D should coincide with division 80 on the scale, and @ 
necessary corrections have been applied to all the observations. 
‘ 3 ae lin- 
! Fraunhofer used no condensing telescope ; he simply placed a prism and cy 
drical lens before the objective of a small telescope and received the wars light 
i upon ¢ ism; being thus to the dimensions of the prism 9s th® 
measure of the io of light examined, he discontinued his observations, propos 
ing to resume the subject at another time. 
