194 S. P. Langley—The Actinie Balance. 
central one, so as to be in identical circumstances of environ- 
extent of range which it is not probable that any chemist’s 
balance can approach. 
Under any circumstances, in view of the measurements we 
expect to make, a very delicate galvanometer of moderate 
(though not the lowest) resistance, will be a suitable instrument. 
e one used is of the most recent form of the Thomson gal- 
vanometer pattern. This instrument, just made by Elliott 
Bros., is more sensitive than any the writer has before used, 
and to its excellence he is no doubt in part indebted for the 
dd 
results attained. 
enough to warm the strips, at the most, as much as 5° C. above 
the temperature of the environment, a 
with the strips actually used by an absolute current of less than 
7 Webers. Even with 4, Webers we have a greater force at 
isposal than the excitant radiation here dealt with could ever 
develop in a thermopile. 
It will be understood that experiments are ages iat (he 
pore to give the preceding description, without waiting for 
urther improvement. It may be observed that the three 
sufficiently to pronounce on with confidence, though it seems 
to promise well. 
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