ic Sia^cm 



29 G Dr. W. Huggins on Photographic Sfi^csia of the Stars. [Feb. 6, 



The same is true of the planets Mars and Jupiter. These two 

 last-named planets do show indications of atmospheric absorption in 

 the visible part of the spectrum. Similar photographs taken of 

 different small areas of the moon under different conditions of 

 illuffiinatioii are negative as to any lunar atmosphere. It must not 

 be supposed that such observations are necessarily antagonistic to the 

 existence of a lunar atmosphere. They simply tell us nothing as to 

 its existence. 



There are many other directions in which the photographic 

 arrangements I have described may be doubtless successfully em- 

 ployed. I hope to photograi>h any lines that may exist in the ultra- 

 violet part of the spectra of the gaseous nebulae. The apparatus will 

 give us the spectra of different portions of a sun-spot. It may enable 

 us to deteimine the difference of velocity in the line of sight of two 

 stars ; and also we may record by it the sun's rotation by the altera- 

 tion in refrangibility of the lines of the spectra of opposite limbs. 



One of the great charms of the study of Nature lies in the 

 circmnstance that no new advance, however small, is ever final. 

 There are no blind alleys in scientific investigation. Every new 

 fact is the opening of a new path. As the descrijption of a first step 

 in a new and broad highway, I venture to hope the last hour's 

 discourse has not been wholly wanting in interest. 



[W. H.J 



