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X. On the Heat produced by Chlorine., and on a singular Effect 

 produced by Lightning, By John Murray, F.L.S. M. W.S. 

 Sfc. 4c- 



To Dr. Tilloch. 



Sir, — JLIr. Hare, of Philadelphia, is stated to have found 

 that tlioughthe thermometer immersed into a volume of chlorine 

 gas is not affected, the sensation of heat on the skui announces 

 it to be 90"* to 100" F. This however I believe only takes 

 place on opening the vessel in contact with atmospheric air. 



This phaenomenon is very ingeniously, and I believe justly, 

 ascribed to a chemical action between the gas and the insensi- 

 ble perspiration of the skin. 



Allow me to add that the same phaenomena are manifested 

 when a volume of nitrous gas is opened into the atmosphere : 

 the thermometer rises only a fraction, but the sensation of heat 

 on the hand is equal to that superinduced by chlorine. 



My feelings deceive me if the same thing does not occur in 

 the case of muriatic acid gas : the quantity which I collected 

 over the mercurial cistern was contained in a small cylinder, 

 and would not admit the immersion of my whole hand. 



I have been much interested in reading an account of " a 

 singular effect produced by a stroke of lightning on the 3d 

 July last, communicated by Professor Pictet to the Helvetic 

 Society." The lightning is represented as having done n<» 

 damage to the house, but " it perforated a piece of white iron 

 with two holes of an inch in diameter, and five inches distant ; 

 and, what was very remarkable, the burs at the edges of the 

 holes were in opposite directions" Professor Pictet draws the 

 conclusion, that either two electric currents had moved simul- 

 taneously, and in opposite directions, or that, alter it had per- 

 forated the metal and moving five inches along it, had pene- 

 trated the plate in an opposite direction. I must confess, how- 

 ever, that to me the latter opinion seems to violate the princi- 

 ples of probability. 



You may remember, sir, that some years ago you were 

 go<Kl enough to insert in the Philosojihical Magazine a com- 

 munication of mine which detailed experiments y>/(r»sf/y simi- 

 lar in the phaenomena pi-esented. 



It may not be irrelevant to advert to two of them. A wire of 

 tlie thickness of a knitting-needle rested on the table, one end 

 iKiiiig ill contiict with the exterior coaling oftlio charged Leyden 

 jar, a card rested on the wire, and a jiatch oftinloil was placed 

 over the further end of tliis wire: another card succeeded, 

 and a liimilar patch oftinloil with a caid and wire al)o\»', ter- 

 minated 



