238 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



low band; and, second, the spectrum of the glowing wire, 

 which is continuous except where crossed by the dark D line. 

 Other metallic lines may be shown dark in the same way. 



Duboscq has called attention to the appearance of relief 

 obtained by projecting a spectrum with a direct- vision 

 prism, using a cross, a V, a ring, or a spiral as the opening 

 for the light. The illusion of relief is very strong in two 

 rectangular planes, a cylindrical surface, etc. The effect is 

 due to the great difference in intensity between the red rays 

 forming the prominent parts of the image and the violet rays 

 which form the more shaded portions of the figure. 



Moser has examined the question whether each chemical 

 compound has a spectrum of its own, as characteristic and 

 definite for it as are those of the elements for them. After 

 giving a resume of what had already been done, mainly with 

 emission spectra, he goes on to describe his own experiments 

 made with the absorption spectra of iodine and bromine as 

 elements, and of nitrogen tetroxide as a compound. From 

 the results obtained he justifies the conclusion that com- 

 pounds have definite spectra, which are measurably inde- 

 pendent of mass and temperature. 



Stoney and Reynolds have studied the peculiar absorption 

 spectrum of the vapor of chlorochromic oxide, which is of 

 special interest because it supplies information as to the 

 duration and character of the motion of the molecules of the 

 vapor which produces it. The spectrum consists of lines of 

 various intensities, but uniformly distributed. Of these 105 

 have been examined, and from their position it has been as- 

 certained that they are all to be referred to one motion in. 

 the molecules of the gas, of which motion they are all har- 

 monics or quasi-harmonics. On the first supposition this 

 motion is repeated 810,000,000,000 times every second in 

 each molecule. From the succession of intensities it is sur- 

 mised that this motion is in some way related to that of a 

 particular point in a violin string vibrating under the influ- 

 ence of the bow, *. e. y a point nearly but not quite two fifths 

 of the string from one of the ends. 



Ilurion has examined in the laboratory of Mascart the 

 spectrum of iodine vapor, and shows that, as Le lioux had 

 observed, this spectrum is produced by anomalous disper- 

 sion, the blue, contrary to the usual order, being less devi- 



