Chemistry and Physics. 139 
cial use in examining faint positive* spectral lines. : 
In another paper the author points out a method of applying 
one of the slits, for example the upper, has a colored glass or 
ese absorbing medium placed in front of it, the spectrum 
of the light will gradually diminish until it becomes exactly equal 
for the two halves of the spectrum at a given part or region of 
once for all. The author promises hereafter a work on the appli- 
cation of the spectroscope to quantitative chemical analysis.—Die 
Anwendung des Spectral-Apparates fir Messung und Vergleich- 
ung der Starke des farbigen Lichtes, Tubingen, 1871; Berichte 
der Deutschen Chem. Gesellschaft, 4ter Jahrgang, No. 6, Pp. a. 
* To avoid cireumlocution, it seems desirable to employ the terms positive and 
negative, to denote respectively bright or dark lines or bands.—w. 6. 
