HANDS PLUNGED IN MELTED COPPER. 351 



to arise from the abundant volatile vapour which is 

 evolved " carrying off rapidly the caloric in a latent state, 

 and intervening between the tar and the skin, so as to 

 prevent the more rapid communication of heat." He con 

 ceives also, that when the hand is withdrawn, and the hot 

 tar adhering to it, the rapidity with which this vapour is 

 evolved from the surface exposed to the air cools it im- 

 mediately. The workmen informed Mr. Davenport, that, 

 if a person put his hand into the cauldron with his glove 

 on, he would be dreadfully burnt, but this extraordinary 

 result was not put to the test of observation. 



But though the conjurers with fire may have availed 

 themselves of these singular properties of individual 

 bodies, yet the general secret of their art consisted in 

 rendering the skin of the exposed parts callous and in-- 

 sensible to heat an effect which may be produced by 

 continually compressing or singeing them till the skin 

 acquires a horny consistence. A proof of this opinion is 

 mentioned by Beckmann, who assures us that in September, 

 1765, when he visited the copper-works at Awestad, one 

 of the workmen, bribed by a little money to drink, took 

 some of the melted copper in his hand, and after showing 

 it to the company, threw it against a wall. He then 

 squeezed the fingers of his horny hand close to each other, 

 held it a few minutes under his arm-pit to make it perspire, 

 as he said, and taking it again out, drew it over a ladle 

 filled with melted copper, some of which he skimmed off 

 and moved his hand backwards and forwards very quickly 

 by way of ostentation. During this performance M. 

 Beckmann noticed a smell like that of singed horn or 

 leather, though the hand of the workman was not burned. 

 This callosity of the skin may be effected by frequently 

 moistening it with dilute sulphuric acid. Some allege 

 that the juices of certain plants produce the same effect, 

 while others recommend the frequent rubbing of the skin 



