98 Di". Schafhaeutl on the Circumstances under ixhicli 



the increase of the wind rose to the highest degree of wet ; 

 the thermometer at the same time falling, which was followed 

 immediately by a separation of water and a flash of lightning, 

 either at the same moment, or following each other at short 

 intervals. It therefore appears that the column of vapour 

 rising from the crater of a volcano seems to be in a similar 

 condition to the fluttering steam issuing from the jet of 

 Marcet's boiler, and the flashes of lightning attributable to 

 the separation of the liquid water from steam and smoke, as 

 I hinted in m}' first communication on this subject, before I 

 was enabled to make these experiments. 



In continuing the above-mentioned experiments, I found 

 that the bundle of wires connected with the electroscope for 

 the absorption of the supposed electricity of the steam, might 

 be dispensed with, and nothing more was necessary than to 

 hold the glass bell against the jet of issuing steam ; and as 

 soon as the peculiar rushing noise commenced, the jet of 

 steam at the same time changing from transparency to a milk- 

 white opacity, the interior of the bell became immediately 

 charged with electricity, whether the bell was 9 or 18 inches 

 distant from the metallic jet. If the inside of the bell be 

 brought whilst in this state into contact with the knob of the 

 electroscope, the gold leaves immediately diverge very vi'idely, 

 and by repeating this experiment several times, a spark may 

 easily be obtained. 



A copper wire inserted through the jet into the boiler^ 

 forming the axis of the pencil of issuing steam, such wire 

 approaching even within an inch of the glass bell, did not in 

 the slightest degree affect the results described ; a further 

 proof that the free electricity which manifested itself was not 

 contained in the issuing steam, but was developed during con- 

 densation in the glass bell. A tinfoif coating on the outside 

 of the bell, reaching within an inch and a quarter of the edge, 

 very considerably diminished the quantity of electricity. When 

 an inch and a half of this coating was removed, the bell acted 

 the same as when entirely uncovered, which may, perhaps, be 

 simply ascribed to the steam on rushing out of the bell coming 

 into contact with the foil when it is so near the edge. 



If the water in the boiler was saturated with common salt 

 or with sulphate of lime, and even a slight excess of sulphuric 

 acid, the angle between the diverging gold leaves remained 

 the same as if distilled water was used. 



From these experiments we may safely infer that the ob- 

 served free positive electricity in this case was solely attribu- 

 table to the sudden condensation and separation of water from 

 steam, caused in my experiment by its coming into contact 



