416 Prof. Wheatstone o?i the Thermo-electric Spark, SfC. 



timony formed into a cylindrical bundle | of an inch in dia- 

 meter and Ij inch in length; the poles of this pile were con- 

 nected by means of two thick wires with a spiral of copper 

 ribbon 50 feet in length and 1^ inch broad, the coils being 

 well insulated by brown paper and silk. One face of the pile 

 was heated by means of a red-hot iron brought within a short 

 distance of it, and the other face was kept cool by contact 

 with ice. Two stout wires formed the communication be- 

 tween the poles of the pile and the spiral, and the contact 

 was broken, when required, in a mercury cup between one 

 extremity of the spiral and one of these wires. Whenever 

 contact was thus broken a small but distinct spark was seen, 

 which was visible even in daylight. Professors Daniell, Henry, 

 and Bache assisted in the experiment, and were all equally 

 satisfied of the reality of the appearance. 



At another trial the spark was obtained from the same 

 spiral connected with a small pile of 50 elements, on which 

 occasion Dr. Faraday and Prof. Johnston were present, and 

 verified the fact. On connecting two such piles together so 

 that the similar poles of each were connected with the same 

 wires, the same was seen still brighter*. 



I conclude, therefore, that the experiment of Antinori is a 

 real addition to our knowledge of electrical phasnomena, and 

 though it was far from being unexpected, it supplies a link 

 that was wanting in the chain of the experimental evidence 

 which tends to prove that electricity, from sources however 

 varied, is similar in its nature and effects, a conclusion ren- 

 dered more than probable by the recent discoveries of Fara- 

 day. The effects thus obtained from the electric current ori- 

 ginating in the thermo-electric pile may no doubt be easily 

 exalted by those who have the requisite apparatus at their 

 disposal. It is not too much to expect, seeing the effects pro- 

 duced by a pile of such small dimensions, that by proper com- 

 binations the effects may be exalted to equal those of an ordi- 

 nary voltaic pile. 



1 shall close this hasty communication with a notice of some 

 experiments on the chemical action of the thermo-electric pile 

 made earlier by Prof. G. D. Botto, of the University of Turin. 

 The form of the pile he employed may suggest some useful 

 hints to those who are inclined to continue the inquiry, as it 

 admits of the application of much higher degrees of heat than 

 one of the ordinary construction does, though the difference of 

 the thermo-electric relations of the two metals employed is not 



• The two piles here employed were made by Mr. Newman of Regent- 

 street. 



