118 ANNUAL OF SCIENTIFIC DISCOVERT. 



of CO couples. These crowns are isolated, and spaced between by 

 washers of amianthus, the whole is stronc^ly bound, by means of 

 3 iron ])iiis, between two circles of iron. The piles constitute then 

 a hollow cylinder, the interior of which it is necessary to heat. 

 The cooling of the junctions, the temperature of which ought to 

 be very low, is effected by simple radiation in the air. The inte- 

 rior cylinder measures 50 millimetres in diameter to as much in 

 height ; the heated surface is, therefore, 78 square centimetres. 



The apparatus is heated by gas, b}'^ means of a specinl burner, 

 which is, properly speaking, only an iron cylinder of 56 millime- 

 tres in diameter, closed at the top, opened at the base, and 

 l)ierccd by little holes upon its convex surface. This cylinder is 

 placed in the centre of the pile. A l)ipe, pierced with little holes, 

 surrounds this cylinder, and distributes the gas in a uniform man- 

 ner around it. 



The gas, arriving opposite the holes of the burner, meets the 

 air, which is blown out by the draught from the iron pipe which 

 surmounts the apj^aratus. Each hole of the burner accordingly 

 forms a blow-pipe, the flame-point of which strikes the opposite 

 side. 



Forty couples of galena and iron have an electro-motive force 

 neighboring that of a Bunsen element. The apparatus that we 

 have described then possesses a force equivalent to one and a half 

 that of a Bunsen element. Between the two electrodes quite visible 

 sparks are obtained. The current reddens a platinum thread of 

 3mm. in diameter at a distance of 35 millimetres; it decomposes 

 water. 



This pile working during 6 consecutive hours consumed 785 

 litres of gas, at a cost of nearly two centimes and a half per hour. 



M. Edm. Becquerel, in some o!)servations on the above pile, 

 says: "The results obtained with the j)receding pile, the dimen- 

 sions of which are restrained, which offers some interest in a sci- 

 entific point of view, and which is of easy use, show that the 

 thermo-electric piles are not yet so economic as one supposes. 

 It is true that the heat produced b}'^ the burner can be better util- 

 ized by putting a greater number of elements around the chim- 

 ney; but, in this condition, as happens with the other thermo-elec- 

 tric piles, the portion of the heat which is utilized in the produc- 

 tion of the thermo-electric current is only a small fraction of that 

 which is communicated to the elements. TJie greater part of 

 the heat is lost by radiation. — Comptes liendiis, May 31, 1809. 



ACTION OF HEAT UPON THE ELECTROMOTIVE FORCE OF PILES. 



Heat exercises a very variable influence upon the electromotive 



force of piles. 



The results of the researches of M. Crova are ; — 



1. That the electromotive force of the elements of the first kind 



(the Daniell type) diminishes regularly when the temperature 



rises. 



