INDUSTRIAL PROGRESS DURING THE YEAR 1875. 1 XV 



the divisions noted by Wollaston. Moreover, Young seems 

 never to have made any experiments to test his theory until 

 some time after he had, on theoretical grounds, adopted it. 



Bunsen has given an account of some new methods in 

 spectrum analysis, in which he has sought to render the use 

 of the spark for obtaining spectra as easy and as general as 

 that of the gas-flame. The first portion of his paper is de- 

 voted to a description of the battery coil and spark appa- 

 ratus required; the second gives the results of his investiga- 

 tions in this way, particularly with the rarer elements. The 

 memoir is accompanied by three spectrum plates, uncolored, 

 showing the spectra of thirty elements and compounds. 



Watts has described a new form of micrometer for use 

 with the spectroscope, in which one of the lines of the spec- 

 trum itself is substituted for the cross wires. This line may 

 be the sodium line, which is almost always present in gas- 

 flame spectra, a hydrogen line with vacua tubes, or a Fraun- 

 hofer line in solar work. This standard line is displaced by 

 a micrometer screw, by which the amount of motion neces- 

 sary to move it from one point of a spectrum to another may 

 be ascertained. The micrometer screw is attached to the 

 upper half of a divided line placed between the prism and 

 the observing telescope, and moves this half over the lower, 

 which is fixed. 



Lockyer and Roberts have investigated the absorption 

 spectra of metals volatilized by the oxyhydrogen flame. 

 They employed a block of lime, in which the metal to be 

 examined was placed, and in which it was volatilized by 

 the oxyhydrogen jet. Through a tube cut in the block the 

 beam of electric light passed, which was viewed by the spec- 

 troscope placed opposite. In this way the absorption pro- 

 duced by the metallic vapor could be observed. They con- 

 clude that in passing from the liquid state to that of perfect 

 gas the molecules pass through diflerent orders of complex- 

 ity, this complexity being diminished by the action of heat, 

 so that each molecular simplification is marked by a dis- 

 tinctive spectrum. 



Goldstein has made some investigations upon the spectra 

 of rarefied gases, which seem to contradict the views of 

 "Wullner. But the latter physicist, in replying to the state- 

 ments of Goldstein, claims that his view, that a line spec- 



