296 A. W. Wright—Spectroscopic Examination 
these lines, with very faint carbon bands, probably due to fatty 
matters employed in lubricating the stop-cocks, invariably ap- 
peared toward the limit of the exhaustion, while lines due to the 
mercury were generally visible during the later stages of the 
rarefaction, having greater or less brilliancy according to the 
temperature of the room. The red hydrogen line is frequently 
dimly visible when the tension has fallen to four or five milli- 
meters, but is neither distinct nor relatively bright until the 
pressure is much less than that, while the other hydrogen lines 
appear distinct only after a much higher degree of rarefaction 
is attain 
containing some carbon, 0°50.+ The chips produced by the 
borer were mostly very small particles. Much of the metal 
* Profs. B. Silliman and T. 8, Hunt, this Journal, II, ii, 370. + Loe. cit. 
