384 Proceedings of Scientific Societies. 



of a pipe connected with the stop-cock on the boiler, a portion of about 

 ten inches in length, near the upper end, being of glass, to produce insu- 

 lation, and the remainder of lead, wound into a helix, like the worm of a 

 still. This helix was immersed in a bucket of water and snow. When 

 the steam was admitted, it became entirely condensed within the pipe, so 

 that there was no rush through the air; yet the production of electricity 

 was as abundant as with the former arrangements. 



Dr. P. took notice of experiments made, half a century ago, by Volta 

 and Saussure, and afterwards by Cavallo, which proved, to their satisfac- 

 tion, that electricity was evolved during evaporation and condensation, 

 but which have since been called in question by Pouillet and others, who 

 assert that a mere change of state, not accompanied by chemical change, 

 never gives rise to electricity. He considered the experiments, now 

 made on a large scale, as favoring, if not confirming, the first opinions 

 entertained on tliis subject. 



Dr. P. referred to the satisfactory manner in w^hich these new experi- 

 ments seem to explain the sources of electricity in the thunder storm, and 

 in volcanic eruptions. 



He then related an experiment in which an insulated iron ball, and 

 afterwards a bar of gold, was heated, and a small stream of water poured 

 on it, so as to be formed into steam at its surface. The first experiments 

 seemed to show that the metal was charged with negative electricity, but 

 subsequent trials threw doubts upon this conclusion. 



Dr. P. also described experiments made to determine whether electri- 

 city was given off during the solidification of liquids, — the sub.stances 

 used being melted lead, silver, and gold. In every case, however, the 

 gold-leaf electroscope failed to exhibit the presence of any electricity. 



Prof. Henry stated that he had not seen the sparks from steam ; but 

 that he had obtained feeble electricity from a small ball, partly filled with 

 water, and heated by a lamp. He agreed with Dr. Patterson in the opin- 

 ion, ti)at the source of the electricity was the change of state, but from 

 water to vapor. There was, however, some doubt on the subject ; Pouil- 

 let had denied the evolution of electricity from the evaporation of pure 

 water. The facts were interesting, particularly on account of the great 

 intensity of the electricity. The results, obtained by the philosophers, 

 which had been mentioned, indicated electricity of very feeble tension, 

 which could only be observed by the most delicnte instruments, but here 

 the sparks w'ere an inch in length. If the vaporization of the water 

 were shown to be the source of the electricity, Prof Henry thought that 

 the phenomena might be readily explained by the beautiful theory of Bec- 

 querel, in regard to the production of the great intensity of the electricity 

 in the thunder cloud. According to this theory, each particle of the 

 vapor carries up with it into the atmosphere the free electricity, which it 

 receives at the moment of the change of state : this, being diffused 



