ee eet ee et 
fT. A. Etlison— Ose of the Tasimeter. 53 
was exposed to heat from any source, it expanded, producing 
pressure upon the carbon button, decreasing its resistance and 
destroying the balance; a current was thus allowed to pass 
amount of this current of course being proportional to the 
expansion of the rubber and to the strength of the battery. 
e form of instrument here described was only finished two 
days before leaving for the west ; hence I was unable to test it. 
However, I set it up upon my arrival at Rawlins, but foun 
that it wasa very difficult matter to balance so delicate an instru- 
the result and also to increase the effect by using two cells in 
place of a single one his device consisted of a rheostat 
formed of two rows of . The rows were about one-half an 
en 
nometer was then shunted, a very feeble current passed through 
it. If the spot of light was not at zero it was brought there by 
either increasing or decreasing the pressure upon the vuleanite 
of the tasimeter by the adjusting nut. When thus brought to 
zero the copper wire of the shunt rheostat was taken off of one 
