baeus.] METHODS OF PYROMETRY. 41 
At this point Pouillet 1 took up these researches. He measured the 
specific heat of platiuum between 0° and 1,U00°, by direct comparisons 
with liis platinum air-thermometer. The data found were so nearly 
constant as to give the calorimetric method of temperature measure- 
ment considerable importance. After a scientific basis had thus been 
given, the method was soon practically developed and many special 
forms of application were devised. Miller 2 describes an apparatus in 
which iron or platinum is quenched in mercury. This apparatus is 
discussed by Schubarth. 3 In an apparatus due to Wilson, 4 platinum or 
even clay is cooled in water. Schinz 5 recommends platinum and water. 
Siemens's 6 data are based on calorimetric measurements with copper and 
water. Bystrom 7 describes a platinum water pyrometer. Weinhold, 8 
who reinvestigated the specific heat of platinum at high temperatures, 
found an anomalous behavior, while that ot iron was quite regular. 
From these results for iron Schneider 9 calculated an extensive table. 
In view of the known anomalous behavior of iron at red heat, the 
regular variation of its specific heat, as compared with that of platinum, 
is certainly very remarkable, and quite at variance with more recent 
results of Pionchon (see below). Salleron's 10 pyrometer makes use of 
copper cooled in water. Special attention is to be given to Carnelley 
and Williams's 11 calorimetric work, in view of the many valuable data 
which these observers deduce by means of it. In their experiment a 
platinum vessel of special form is heated to the unknown temperature 
and then quenched in water. Fischer's 12 calorimeter again is adapted 
to furnace uses — cooling in water. Hobson 13 and, more thoroughly, 
Bradbury, 14 endeavored to apply a new method of calorimetric pyrome- 
try. They cool the hot air of the blast with a known amount of cold air 
and measure the resulting temperature. 
Thereupon Violle 15 began to publish the researches to which refer- 
ence has already been made. By investigating formulated relations 
1 Pouillet: C. R., vol. 3, 1836, p. 782. 
2 Miller : New Philos. Jour. Edinburgh, vol. 44, 1848, p. 126 ; Dingler's Jour., vol. 108, 
1848; p. 115. 
3 Schubarth : Dinger's Jour., vol. 110, 1848, p. 32. 
4 Wilson: Philos. Mag., London, 4th series, vol.4, 1852, p. 157; Dingler's Jour., vol. 
158, 1860, p. 108. 
5 Schinz : Warme-messkunst, 1858, p. 53. 
^Siemens: Dingler's Jour., vol.217, 1875, p. 291. 
7 Bystrom: Mechanics' Jour., 2d series, vol. 8, 1862, p. 15 ; Fortschritto d. physik, 
1862, p. 344; ibid., 1863, p. 355. 
b Weinhold: Pogg. Ann., vol.149, 1873, p. 186. 
9 Schneider: Zeitschr. des Vereins Deutscber Ingen., 1875, p. 16. 
10 Salleron : Sci. Am., 1875, p. 50. 
11 Carnelley and Williams : Jour. Chem. Soc. London, vol. 1, 1876, p. 489. 
12 Fischer: Dingler's Jour., vol. 225, 1877, p. 467. 
13 Hobson: Ibid., vol.222, 1876, p. 46. 
14 Bradbury: Ibid., vol. 223, 1877, p. 620. 
16 Violle: C. R., vol. 85, 1877, p. 543; Philos. Mag. Lond., 5th series, vol. 4, 1877, p. 
318; C. R., vol. 87, 1878, p. 981; Ibid., vol. 89, 1879, p. 702. 
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