320 



THERMO-ELECTJRIC MEASUREMENT OF HEAT. 



it is then suddenly cooled, and shaken at the same time, so that the thread of mercury is 



_^^_____ TTT __^ thereby suddenly broken 

 vvm ,iHuun i r M.M u i .ii n. i ii,.n. .i.p..|.. T "r"i ~ ^\ a |j 0ve 40. The tube is so 



* < W5 1* ^ narrow that 1 C. is equal 



Fig. 228. 

 A, C'assella's "infallible," B, "Ferris' perfect," and C, Evans' and Wormull's "standard" 



clinical thermometers. 



to about 10 centimetres of the length of the tube, so that T ^ C. is still 1 millimetre in 

 length. The scale is divided empirically, but the value of the divisions must be com- 

 pared with a normal ther- 

 7 mometer. 



T Kronecker and Meyer 



used very small maximal 

 "outflow thermometers," 

 and caused them to pass 

 through the intestinal 

 canal, or through large 

 blood-vessels. The mer- 

 cury flows out of the short 

 open tube, and of course 

 more Hows out the higher 

 the temperature. After 

 these small bulbs have 

 passed through the animal, 

 a comparison is instituted 

 with a normal thermo- 

 meter, to determine at what 

 temperature the mercury 

 reaches the free margin of 

 the tube. 



B. Thermo-electric Me- 

 thod. This method en- 

 ables us to determine the 

 temperature accurately and 

 rapidly (fig. 230, I). The 

 thermo-electric galvano- 

 meter of Meissner and 

 Meyerstein consists of a 

 circular magnet (in), sus- 

 pended by a thread of silk 

 (c), to which a small 

 mirror (S) is attached. A 

 large stationary bar mag- 

 net (M) is placed near the 

 magnet (m), so that the 

 north poles (n and N) of 

 both magnets point in the 

 same direction, and it is so 

 arranged that the sus- 

 pended magnet is caused 

 to point to the north by a 

 minimal action of M. A 

 thick copper wire (b, b) is 

 coiled several times round 

 m (although in the fig. it 

 is represented as a single 

 coil), and the ends of the 

 wire are soldered to two thermo-elements, each composed of two different metals iron and 



Fig. 229. 

 Walferdin's 

 metastatic 

 thermo- 

 meter. 



A B 



Fig. 230. 



Scheme of thermo-electric arrangements for 

 estimating the temperature. 



