Dr. Hare's Defiagraior and Calnrimotor. 101 



charcoal, or potash. Upon these substances, the excite-' 

 ment by water has no influence, but to the sensation is pain- 

 ful, though it maybe borne longer, than when acid is used* 

 Neither is the shock greater, in any sensible degree, at the 

 moment of immersion, than afterwards. The effect upon 

 the electrometer, is at least as great, with water, as with 

 acid. Immediately over any of the most turgid veins, where 

 the skin is tender, as on the back of the hand, will be found 

 the greatest sensibility. The positive pole, is most capable 

 of producing pain. This I had frequent opportunities of 

 ascertaining, by the observations of those who, not knowing 

 how to distinguish it from the negative pole, could not have 

 been biassed in their opinion. Upon a common gold leaf 

 electrometer,a defiagratorofSOOpairswill havenoinfiuence. 

 I have constructed one by means of a bottle, a single slip of 

 gold leaf, and a knob at right angles to it, supported by a 

 screw, so as to be easily moved nearer to or further from the 

 leaf. The wire from which the latter is suspended, passes 

 through a cork in the neck of the bottle. The screw en- 

 ters through a nut, cemented into a hole drilled on one side. 

 When the wire which supports the leaf, is fastened to one 

 of the poles, every time the screw is touched by the other, 

 the leaf v^^ill strike the ball provided the distance be very 

 small, perhaps not greater than the tenth of an inch. This 

 result was obtained at a greater distance when the coils had 

 been recently withdrawn from the acid, than when they are 

 covered by it. I have known a piece of dry sealing wax, as 

 big as a chesaut, without friction, to affect this electrometer 

 as much as my largest deflagrator. 



A magnetic needle was very powerfully disturbed by the 

 deflagrator, under all its forms. The celerity with which 

 the galvanic surfaces may be immersed in, or withdrawn 

 from the acid, contributes much to economy, and to the 

 ease of the operator in galvano-magnetic enquiries. 



The prevalent notion, that the intense light and heat 

 produced by galvanic action, are results secondary to elec- 

 tricity, the presence of which is at times only indirectly dis- 

 coverable, the more surprises me ; since it does not in the 

 smallest degree, elucidate the primary operation, by- which 

 this principle is alleged to be evolved. According to 

 some philosophers, the contact of the metals alone, accor- 

 ding to others this contact accompanied by their solution, 

 <^volves electricity in quantity sufficient to extricate heat 



