42 MEASUREMENT OF HIGH TEMPERATURES. 
between specific beat and temperature almost as far as 2,000°, be made 
silver, gold, copper, palladium, platinum, and perbaps iridium, availa- 
ble for tbermal measurement. V. Meyer 1 before adopting Graft's sug- 
gestion bad measured bis temperatures calorimetrically. In America, 
practical calorimetric temperature measurement was studied witb mucb 
success by Hoadley, 2 wbo describes an apparatus and tbe precautious 
to be observed. Like Violle, be endeavors to arrive at tbe melting 
point of platinum, and finds a small value of about 1,600 0. Mr. 
Hoadley, however, questions tbe purity of bis platinum. An elaborate 
research published by Ehrhardt 3 proposes to find the specific heat of 
"iodides, bromides, aud chlorides throughout large ranges of tempera- 
ture. Ehrhardt measures his temperatures with the porcelain air- ther- 
mometer and carries his investigations as far as 600°. 
Finally, I desire to advert to an important research by Pionchon. 4 
This observer makes a special study of the specific heat of iron between 
0° and 1,000°, and finds a regular cubical formula to obtain between 0° 
and 655°. Between 660° and 723° the increase is much more rapid, 
and between 723° and 1,000° the relation is nearly linear. This inter- 
esting result adds a new anomaly to the behavior of iron at red heat, for 
in the last mentioned interval (723°-l,000°) the specific heat of iron 
is nearly double that which holds for tbe first interval. 
Ebullition. — Eeference to high temperature boiling points has already 
been made in the sections on air thermometry. Full data are given in 
the tables of Carnelley and of Landolt u. JBcernstein, just mentioned. In 
this place I desire to call attention to the data of Crafts, 5 in which, by 
using napthaline and benzophenol, temperatures of ebullition between 
140° and 350° are obtainable by tbe mere variation of pressure from 
8.7 cm to 230 rm . 
Heat conduction. — A simple device for a thermostat is made by 
Jourdes 6 who inserts a bar of metal into the furnace and measures tbe 
temperatures at points cold enough for the mercury thermometer. Heat 
is conveyed along tbe bar by conduction, and there are cavities to re- 
ceive the thermometers, A somewhat different attempt of this kind is 
due to Main, 7 who surrounds a mercury thermometer bulb with asbes- 
tos and exposes it for stated lengths of time. Very elaborate attempts 
to determine the temperature on the inner surface of a furnace wall, by 
measuring the temperature of the outer surface under known conditions 
of conductivity, were published by Scbinz. 8 Following a method origi- 
1 Meyer: Berl. Ber., vol. 12, 1879, p. 1426. 
2 Hoadley: Jour. Franklin Inst., 3d series, vol. 84, 1882. 
3 Ehrhardt: Wied. Ann., vol. 24, 1885, p. 215. 
4 Pionchon: C. R., vol. 102, 1886, p. 1454. 
6 Crafts: Nature, vol. 26, 1882, p. 466. 
6 Jourdes: C. R., vol. 51, 1860, p. 68; Dingler's Jour., vol. 157, 1860, p. 151. 
7 Main: Ibid., vol 221, 1876, p. 117. 
8 Schinz : Dingler's Jour., vol. 163, 1862, p. 321 ; ibid, vol. 177, 1865, p. 85. 
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