S. P. Langley—The Actinic Balance. 193 
this is particularly noticeable in the strips which offer large 
resistance in small compass. There is then a practical limit 
beyond which we cannot go without the battery heating of the 
strips becoming prejudicial, but the paradox we have alluded 
to is so near to fact, that it is found to be the case in actual 
ance, and a relatively strong current. The latter construction 
is far easier, but particular considerations have determined the 
actual trial of the former plan (of higher resistance and feeble 
currents) in the instruments employed. 
ing cylinder is warmed or cooled, each system is warmed or 
cooled in an equal degree, and the galvanometer needle remains 
unmoved. 
It is found in practice often more convenient not to use the 
In the prolongation of its axis enters it, the galvanometer 
Strument will instantly respond, while it remains unmoved 
all accidental surrounding radiations. A still further im- 
provement in the disposition of the strips is made by leading 
one of them in the center of the cylinder and by dividing the 
other into two equal parts, which are left one either side of the 
