560 Mr. 8, C. Laws on the Thomson Effect 
(6) Applying experimental results to the expression given 
by J. J. Thomson for the loss of energy per centimetre (due 
to radiation) in passing through a medium containing ions, 
; sn (Re 
and taking the negative corpuscles with — =7x10° and 
m 
e=10-° as the sources of the radiation, the number of these 
corpuscles or electrons per c.c. for air under normal conditions 
is of the order 10”. 
(7) * Quantitative results show that the secondary radiation 
from metals, though of different penetrative power, is of the 
same nature as the primary X-radiation. 
(8) Results of the order of magnitude of those given above 
have been obtained with all metals experimented upon, though 
the secondary radiation from them differs considerably in 
character from the primary. 
University of Liverpool. 


LXII. The Thomson Effect in Alloys of Bismuth and Tin. 
By 8. C. Laws, B.A., B.Sc., St. John’s College, Cambridge; 
1851 Evhibition Scholar ™*. : 
I. Introductory. 
XPERIMENTS on some of the electrical properties of 
Bismuth-Tin alloys have already been made by Roll- 
mann t, von Httingshausen and Nernst f, Hutchins §, 
Spadavecchia ||, and Schulze 4. 
The very interesting nature of the results obtained seemed 
to warrant a further study of the electrical behaviour of these 
alloys. 
The present communication contains an account of some 
experiments on the Thomson effect, or the amount of heat 
evolved or absorbed by a current in passing along a conductor 
in which a temperature-gradient is maintained, in such 
alloys. 
As is well known, this effect was first observed by 
Lord Kelvin **, who found that heat was evolved by a current 
passing down a temperature gradient in copper, whilst in 
iron an absorption of heat took place under similar circum- 
stances. 2 
“4 
* Communicated by Prof. J. J. Thomson. / “Wy 
+ Rollmann, Pogg. Ann. lxxxiil. p. 78 (1851). 
{ Von Ettingshausen & Nernst, Wied. Ann. xxxiii. p. 477 (1888). 
§ Hutchins, Amer. Jour. of Sci. xlvili. p. 226 (1894). 
|| Spadavecchia, Nuov. Cim. ix. p. 482 (1899). 
@ Schulze, Ann. der Phys. 1x. p. 558 (1902). 
*& W, Thomson, Phil. Trans. exlvi. p, 649 (1856). 
ee nnd 

