138 Experiments en the Oxidation of Metals by EUHrlcltj. 



be fet into tlie water, care being taken to let it remain a fufficient length of time that the 

 air in the infide may become of the fame temperature, which will be {hewn by the gages 

 being (lationary. If this circumftance be not obferved with great attention, errors in the 

 conclufion will be the confequence. 



EXPERIMENT I. 



A fufficient quantity of leaden wire, of ^'gth part of an inch diameter, was bound to a 

 cord at different places about four inches dillant, as has been already mentioned, and 

 wound upon the axis of the wheel in p q-, the end of it, by means of the long brafs needle, 

 was drawn out at the top of the receiver through the tube' in, which was fcrewed in its 

 place, and the cord drawn tight, as reprefented at A. The cocky was then clofed, and the 

 whole inftrument fet in the water fo deep, that the brafs plate was about one inch under 

 the furface Qf the water. The cocks n were opened to admit the external air into the 

 receiver, as the air within became condenfed by the coldnefs of the water. When it had 

 remained nine minutes under the water, the gages were fcrewed on to the cocks perfeftly 

 air tight, and both appearing flationary, the docks were fliut. The inftrument was then 

 taken out, wiped dry, and fet as near the ele£lrometer, Fig. 2, as poflible, not to in- 

 fluence the motion of the ball A, namely, at the diftancc of about one foot. One end of a 

 wire, a h, was hooked to the cock w, and the other to the hook of the electrometer.* One 

 end of another brafs wire, s t-, was hooked to the cocky", and the other end made to 

 touch the outfide of the battery, Fig. i, whicli is compofed of fifteen jars, containing 

 about feventeen fquare feet f coating, and connedled with the eledlrometer by means of a 

 wire L. The battery was charged till the ball A of the eleftrometer, which was loaded 

 with twenty-fix grains, defcended and dire£ted the difcharge through the wire h, which 

 was converted into a bluellh white impalpable powder, at firft appearing like a white 

 cloud, and filling the whole receiver (the cord was left entire) ; the inflrument was then 

 releafed from the ele£l:rometer, and fet in the water as before. After it had remained 

 there five minutes, the cocks under the gages were opened. No change could be perceived 

 in the mercury gage, but a motion in the water gage was juft perceptible. Hence I 

 concluded that the powder thus produced had abfoibed no air. 



EXPERIMENT II. 



The apparatus was taken out of the water, and another length of wire drawn forward, 

 and placed at the eleftrometer and battery as before ; the battery was charged till the elec- 

 trometer caufed the difcharge, which again produced the powder. The apparatus was not 

 put into the water as before, but was left to remain till another length of wire was drawn 

 iorward, and the difcharge direded through it. And this procefs was repeated in the 



* For a defcription of this eleiStrometer, fee this Journal, II, 528, 

 f For an account of this battery, fee Journal, II. 5SC. 



whole 



