82 Dr. W. A. Miller on some Cases of Lines 



crossed through a great portion of its extent by numerous 

 equidistant lines, corresponding both in number and position 

 in the two substances. 



This remarkable similarity of action upon light, between 

 bodies whose chemical properties are in many respects so 

 closely allied, induced me, as the subject appeared to have 

 been completely laid aside by the philosophers to whom these 

 observations are due, to examine a variety of other coloured 

 compounds. I was in hopes of discovering, amongst other 

 bodies, and particularly amongst compounds of similar nature 

 and properties, a correspondence, if not in the colorific posi- 

 tion, at least in the general arrangement of the lines (if any 

 were produced), which are rendered visible by a prismatic 

 analysis of the light that has been transmitted through the 

 different coloured media. This hope, however, I have not 

 been able to realize to any considerable extent. But though 

 the lesults obtained are many of them negative, as the cases 

 in which no lines occur are much more numerous than 

 those in which they are produced, I have met with some facts 

 which I believe are not generally known, and which may, 

 therefore, possess sufficient interest to warrant my submitting 

 them to the consideration of men of science. The mere enu- 

 meration of the substances in which I have failed to discover 

 them may, besides saving others some fruitless labour, be of 

 some value. 



My observations may be referred principally to two heads, 

 those which relate to the effect of coloured gases and vapours 

 upon transmitted light, and those which arise from expe- 

 riments on the spectra produced by tiames of different co- 

 lours. 



Before detailing the mode in which the following experi- 

 ments were conducted, I will briefly state the principal results 

 which I have obtained from the first series. 



1. In no case where colourless gases are employed, have I 

 detected any additional lines. Fourteen different substances 

 were employed, varying in density from that of hydrogen, 

 0*069], to that of aether, 2'586', and hydriodic acid, 4-388. 

 Of these bodies three were simple, viz. oxygen, hydrogen and 

 nitrogen, and eleven were compounds, varying greatly in their 

 mode of condensation, as in binoxide of nitrogen, where the 

 elements unite without condensation ; protoxide of nitrogen, 

 where three volumes of the gases become two; and ammonia, in 

 which two volumes are condensed into one; in chemical pro- 

 perties they differed not less widely. Five of these gases were 

 acid, the carbonic, hydrosulphuric, hydrochloric, hydriodic, 

 find sulphurous acid. One ammonia is alkaline, one cyano- 



