52 T. A. Edison— Use of the Tasimeter. 
tT. V.—On the use of the Tasimeter me meote : the Heat of the 
eet and of the Sun’s Corona ;* by THomas A. Epison, Ph.D. 
To Professor Henry Draper M.D., Director of the Draper Eclipse Expedition :— 
Dear Sir: The instrument which I used at Rawlins, Wyo- 
ming, during the solar eclipse of July 29, 1878, for the purpose 
of measuring the heat of the sun’s corona, was devised by me a 
to allow me to give it as thorough a test as was desirable to 
ascertain its full capabilities and characteristics. 
This instrument I have named the tasimeter, from the Greek 
words taozc, extension, and petpor, measure, because primarily 
the effect is to measure extension of any kind. The form of in- 
strument which I used is shown in the annexed wood-cut (fig. 1.) 
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With this instrament was aed a Phossen's Selina galva: 
nometer, on a tripod, and having a resistance of three-fourths of 
an ohm. The galyanometer was placed in the bridge wire of 9 
W heatstone balanee, two of the branches of which had constant 
resistances of t ms each, while of the other two one had 3 
constant of stiles eee and the other contained the tasimete! 
which was adjusted by means of the screw to three ohms § 
When thus balanced if the strip of vulcanized rubber placed f 
between the fixed point and the carbon button (seen in fig. 2) 4 . 
* Read, by permission of Dr. Draper, at the St. Louis meeting of the Americal o 
sgociation. c 
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