Condensation with Lightning and the Aurora. 105 



discharged with the steam, which was effected by giving the 

 condenser time to cool before an experiment was made. 



76. It is now seen that a simple alteration of the pressure 

 is sufficient to change the electrical state of the boiler from 

 negative to positive, and the steam from positive to negative ; 

 and this takes place not in any adventitious manner, for I 

 could as easily and with equal precision make the boiler posi- 

 tive as negative. 



77. A platinum blowpipe jet was united to the apparatus 

 for producing an artificial fountain by condensed air; the jet 

 was fixed rectangularly to the pipe of the fountain, and its 

 aperture was very fine ; so that when the water was ejected 

 under a pressure of four or five atmospheres, the stream be- 

 came divided, at a distance of about 12 to 18 inches, into a 

 stream of fine drops. It was found advisable to keep a very 

 fine piece of platinum wire in the aperture of the blowpipe 

 jet, as it prevented its becoming stuffed up, and by moving 

 the wire I could greatly vary the shape of the discharge. 

 The fountain itself consisted of a brass cylinder about 7 inches 

 long and 3 inches diameter, with the two fiat ends soldered 

 on. I think this construction should never be employed ; for 

 the varying flexion, though invisible, of the brass ends, the 

 thickness of which cannot be seen, appears gradually to de- 

 stroy the continuity of the solder, and the instrument becomes 

 liable to burst, as mine has done. 



78. The larger collector was held by a tube-holder, and 

 connected with the single-leaf electrometer, and water was 

 discharged from the fountain through the platinum jet so that 

 the drops might fall on the wire-gauze, the distance between the 

 gauze and the jet being from one to two feet ; the electrometer 

 became charged positively. The intensity of the charge was 

 very variable, depending on the form of the aperture of the 

 jet: when the water issued as a compact stream, the electri- 

 city was strong; but when the platinum wire was so placed 

 that the discharge flew into minute drops almost as soon as it 

 left the jet, there was always very little or no electricity ob- 

 tained. When the distance between the jet and gauze was 

 diminished to 3 or 4 inches, there was no electricity produced. 

 Distilled and common water were used with about equal effect 

 in these experiments ; and I found, too, a brass jet might be 

 substituted for one of platinum. This species of electricity 

 was during my experiments frequently so abundant, that I 

 doubt whether a jet of water, properly discharged, perhaps 

 through an Armstrong's jet, would not be a better source of 

 electricity than a jet of steam. 



79. The fountain being insulated, the discharge of the water 



