82 Mr. J. Brown. [June 16, 



lamp from one side of the cell to the other. A silver chloride cell of 

 the same form gave a similar result. Lead was tested in the fused 

 state in two asbestos-plugged tubes, like B, fig. 1, immersed in a 

 V-tube containing fused lead chloride. The other easily fusible 

 metals, tin, cadmium, and zinc, were tested in W-shaped tubes, open 

 at the apex in the middle, for introduction of the chloride after the 

 metal had been fused in the two lower bends. With all the easily 

 fusible metals, except zinc, the tubes were made sufficiently long to 

 allow the portion of metal surrounding the copper connecting wire 

 to remain solid, so as to avoid risk of alloying from long fusion in 

 contact with the copper. 



In all cases, except cadmium, with which in three carefully-made 

 experiments, I found no decided effect, the hotter metal was found 

 to be the negative pole of the arrangement. Zinc was somewhat 

 doubtful, and may have been influenced by alloying with the copper 

 connection. 



To give some idea of the magnitudes of the electromotive forces of 

 these thermal cells, the results of these rough experiments are given 

 in column A below. In column B are the corrections employed in 

 Table II for comparison. 



A. B. 



Silver O07Daniell 0'273 



Copper 0-10 0*23 



Tin 0-01 0-093 



. Lead 0-015 0-099 



Cadmium O'OO O'OO 



Zinc 0-02? 0-049 



There is a kind of rough correspondence between the numbers in 

 the two columns, but the inexact nature of the experiments of column 

 A precludes a strict comparison. 



I had no means of measuring, otherwise than by rough estimation, 

 the difference of temperature between the two sides of the cells ; but 

 as a mere approximation it might be taken for tin as rather less than 

 the difference between the freezing and boiling points of stannous 

 chloride, or say 300 C. ; for zinc and copper it was rather more than 

 this, and for lead and silver less, as their chlorides are less easily 

 fusible, and the higher temperature was limited to the softening point 

 of the glass tube. 



Besides the experiments of Gladstone and Tribe mentioned above, 

 others bearing less definitely on the subject have been made by 

 Andrews,* Hankel,f and more recently by Mr. T. Andrews,! of 

 Sheffield. 



* ' Phil. Mag.,' ser. 3, vol. 10, p. 433, 1837. 

 t ' Pogg. Ann.,' vol. 103, p. 612, 1858. 

 $ ' Eoy. Soc. Proc.,' vol. 38, p. 216, 1885. 





