Dr, Matthiessen 07i the Thermo-electric Series. 221 



power of No. 1 is owing, as Professor Bunsen thinks, to a small 

 quantity of suboxide being dissolved up in it. 



Graphite No. 1 is the so-called pure Ceylon ; No. 3 purified Ger- 

 man, and No. 2 a mixture of both. The specimens were purified by 

 Brodie's patent and pressed by Mr. Cartmell, to whom 1 am indebted 

 for the above. 



The conducting power for gas-coke, graphite, and Bunsen' s bat- 

 tery-coke increases by heat from 0° to 140° C. ; it increases for 

 each degree 0-00245, i. e. at 0° C, the conducting power =100, and 

 between the common temperature and a light red heat about 12 per 

 cent. The following metals were chemically pure : — Silver, gold, 

 zinc, cadmium, tin, lead, antimony, quicksilver, bismuth, tellurium. 

 Those pressed were sodium, zinc, magnesium, calcium, cadmium, 

 potassium, tin, lead, strontium, antimony, bismuth, tellurium, and 

 the alloys of bismuth-antimony and bismuth-tin. The way in which 

 these wires were made is described in the 'Philosophical Magazine' 

 for February 1857. 



" On the Thermo-electricSeries." By Augustus Matthiessen, Ph.D. 

 Being enabled by the method described in the ' Philosophical Ma- 

 gazine' (Feb. 1857) to obtain wires of the metals of the alkalies and 

 alkaline earths, I have determined their places, together with those 

 of most of the other metals, in the thermo-electric series. 



If A, B, C are different metals, and (AB), (BC), (CA) the 

 electromotive powers of thermo-elements formed out of each two of 

 these metals, whose alternate soldering points are at two different 

 temperatures, so is (AB) -|- (BC) -i- (CA) = 0, and therefore 

 (AB)=a-i, 

 (BC) = i-c, 

 (CA) = c— a, 

 where the values a, b, c not only depend on the two temperatures, but 

 also on the nature of each of the metals A, B, C. As the differences 

 of the same constitute the electromotive powers, the value for either 

 of these metals may be put = 0. 



If the temperatures of the soldering points of a thermo-element 

 only vary slightly, the electromotive powers may be said to be in 

 ratio with the difference of the two temperatures, and under the 

 same conditions the values a, b, and c are also in ratio with the 

 difference of the temperatures, and their relations to each other 

 therefore independent of the same. 



If now the value of the second metal relative to the above value 

 of the first be taken equal to 1, the values of the others, in relation 

 to these, become constants, and only depend on the nature of each 

 metal ; these values I will call the Thermo-electric Constants. The 

 results obtained are given in the following Table, where the thermo- 

 electric constant of chemically pure silver is taken = 0, and that of 

 a certain commercial sort of copper = 1 . 



Bismuth (commercial, pressed wire) -|-35'81 



Bismuth (pure, pressed wire) -f 32"91 



Alloy of 32 parts of bismuth and 1 part of antimony (cast) -(-290G 



