A. W. Wright on the cganit of the Electrical Machine. 381 
oral requires 18°66 per cent nitrogen and 6°66 per cent 
- seams cham 
Tt can hardly be doubted that further improvements in the 
process will render it possible to determine in a single analysis, 
carbon, hydrogen and nitrogen with greater facility and accu- 
racy than nitrogen alone can be determined by the older methods. 
In conclusion I may state that the Sprengel pump may be ap- 
plied with great advantage to the determination of the amount 
gas given off from various substances by the simple applica- 
tion of heat. 
Art. XLV.—On a peculiar form of the discharge between the 
sr rs the Electrical Machine ; ; by ArtHuR W. WRIGHT, 
Prof. of Physics and Chemistry in Williams College. 
WHEN the Holtz electrical machine is —re at a high ten- 
a but without the — if _ istance between the 
high tension may attain a length of several at aC it 
If now the finger or some other gene be interposed between 
~~ poles, the a is interru and a silhouette of the object 
the dthelike. € 
of nin andthe may be called an el-ctrical shadow, to 
a real a that I had many times noticed it casually, a 
‘using the machine in a dimly ighted room, without suspecting 
