34-4 Chlorine — Radiation, fyc. 



from some thunderstroke, from whose effect, the experi- 

 menter is happy if he escape uninjured. — Editor. 



N. B. In the first experiment, related in this notice, the 

 flask was not covered while filling, but it was done in an 

 under-ground laboratory, where the light was imperfect J- 

 in the second experiment, the flask was filled in an upper 

 room, when the sun shone out of doors, but the flask was 

 covered by a thick towel: in the third, although in an upper 

 room, it being a very dim light, no precaution was used, and 

 the glass was not covered ; on the other hand, there was no 

 heat from any adventitious cause, nor could the effect be at- 

 tributed to any thing peculiar, for we had made this mixture 

 many times before, under similar circumstances, without any 

 explosion. — Ed. 



2. Chlorine produces heat in the skin. 



(Communicated, in a letter, dated Philadelphia, Oct. 9, 1820, from Professor 

 Hare to the Editor.) 



I find, among the obvious quahties of chlorine, one which, 

 I believe, has never been mentioned as such. The air 

 around being at about 60, it produces a sensation of heat 

 equal to 90 or 100, on immersing the hand in it, though the 

 common thermometer should not be affected when im- 

 mersed. The differential thermometer shewed the gas 

 slightly warmer; but the effect thus indicated was too small 

 to have affected the hand, and possibly may arise from 

 chemical action on the atmospheric air, with which it com- 

 municates, or the moisture in it. Perhaps a sort of chemical 

 action takes place, between the gas and the insensible per- 

 spiration of the skin, as the power of chlorine in decompos- 

 ing animal effluvia is well known. 



3. Radiation of Heat through Glass. 



I neglected to mention to you, that I had, about two years 

 ago, two large brass mirrors, sixteen inches diameter, one 

 foot focus, accurately turned by a fixed radius of two feet. 

 By these, an incandescent ball of iron, about three inches 

 diameter, being placed in one focus, phosphorus was igni- 

 ted, in that of the other, at the distance of sixty feet. But 



