ELECTRICAL EXCITEMENT BY AIR, OIL, POWDERS, ETC. 
29 
let suddenly out against the brass or the wood cone ( 20 77.), it rendered the cone 
negative, exactly as the steam and water had done (2097-)- This I attributed to the 
particles of water suddenly condensed from the expanding and cooled air rubbing 
against the metal or wood : such particles were very visible in the mist that appeared, 
and also by their effect of moistening the surface of the wood and metal. The elec- 
tricity here excited is quite consistent with that evolved by steam and water : but the 
idea of that being due to evaporation (2083.) is in striking contrast with the actual 
condensation here. 
2131. When however common air was let out against ice it rendered the ice positive , 
again and again, and that in alternation with the negative effect upon wood and 
metal. This is strongly in accordance with the high positive position which has 
already been assigned to water ( 2107 .). 
2132. I proceeded to experiment with dry air (2129.), and found that it was in all 
cases quite incapable of exciting electricity against wood or sulphur, or brass, in the 
form of cones (2077- 2097.) ; yet if, in the midst of these experiments, I let out a por- 
tion of air immediately after its compression, allowing it no time to dry, then it ren- 
dered the rubbed wood or brass negative (2130.). This is to me a satisfactory proof 
that in the former case the effect was due to the condensed water, and that neither 
air alo?ie nor steam alone can excite these bodies, wood, brass, &c., so as to produce 
the effect now under investigation. 
2133. In the next place the box C was attached to this air apparatus and experi- 
ments made with different substances introduced into it (2108.), using common air 
as the carrying vehicle. 
2134. With distilled water in C, the metal cone was every now and then rendered 
negative, but more frequently no effect was produced. The want of a continuous 
jet of air sadly interfered with the proper adjustment of the proportion of water to 
the issuing stream. 
2135. With common water (2090.), or a very dilute saline solution, or very dilute 
sulphuric acid (2091.) or ammonia, I never could obtain any traces of electricity. 
2136. With oil of turpentine only in box C, the metal cone was rendered positive; 
but when both distilled water and oil of turpentine were introduced, the cone was 
very positive, indeed far more so than before. When sent against ice, the ice was 
made positive. 
2137- In the same manner olive oil and water in C, or resin in alcohol and water 
in C, rendered the cone positive, exactly as if these substances had been carried for- 
ward in their course by steam. 
2138. Although the investigation as respects the steam stream may here be con- 
sidered as finished, I was induced in connection with the subject to try a few experi- 
ments with the air current and dry powders. Sulphur in powder (sublimed) rendered 
