186 C H E M ] 
be alfo necefiary to know the capacities of the bodies for 
caloric. The conducing powers would be diredtly as the 
capacities, and inverfely as 1 the times, when the chan¬ 
ges of temperature were equal. But in the attempts that 
have been hitherto made to calculate the permeability of 
bodies to caloric, the confideration of their capacities 
has been uniformly negledted ; and in many of Sir B. 
Thompfon’s experiments, unequal weights of different 
fubilances were ufed, and no attention afterwards paid 
to this difference in calculating the conducting powers, 
Be makes, for example, the conducting power of mer¬ 
cury : conducting power of water : : 1000 : 313; but in 
the experiments from which this eftimate is taken, he 
had ufed equal volumes of the water and mercury, and 
conlequently had communicated the fame increafe of 
temperature to more than thirteen times as much mat¬ 
ter in the one experiment as in the other. 
The following table of the condudtingpowers of differ¬ 
ent fubilances is taken from the Journal de Fhyfique for 
OCfober 1793. It is there given as the tranflation from the 
German of an efihy by Humboldt, on the Conducting 
Powers of different Bodies for Caloric. From the fliort ac¬ 
count prefixed to it in the Journal de Phyfique, it would 
appear to be defective in this refpeCt, that the conduct¬ 
ing powers of the fubilances which it contains have been 
calculated without regard to the differences of their ca¬ 
pacities; but, as it is the lateit and molt co'mprehenfive 
table of the kind, it has been thought the molt proper 
for inlertion. It is necefiary to mention, that the con¬ 
cluding powers given in the table refer to the fame vo¬ 
lumes, and not to the fame weights, of the fubilances 
enumerated. 
TABLE OF CONDUCTING POWERS. 
Conducing Media. 
Specific 
Gravities. 
C rowI? e Authorities. 
Torricellian vacuum 
o'i76oSirB.Thomp- 
Atmolpheric air, denfity 
= 1 
*0012 
o-2 55oThefame[fon 
Rarefied air, denfity= 
1“ 
24th 
0-2490 The fame. 
Wood allies . . • 
1-556° 
0-7072 Humboldt. 
Sulphuric acid . . 
1*7000 
0-7764 
Rult of iron . . . 
4*5000 
0*8889 
Copper .... 
8-5760 
0-8970 Richmann. 
Iron. 
7-8076 
0*9430 
Brafs. 
8-3960 
.0-9430 
Cow’s milk . . . 
1*0300 
0-9727 Humboldt. 
Vinegar .... 
1*01 TO 
0-9900 Mayer. 
Water .... 
I OOOO 
1*0000 
Gold. 
I 9*0400 
1-0504 Humboldt. 
Moilt air . . . 
1-0543 Tliompfon. 
Nitrous acid . . 
1-5800 
1-0989 Humboldt. 
Silver. 
10*0010 
1-2195 
Muriatic acid . . 
1*1 500 
1-2787 
Calcareous earth . 
2-8570 
*•3674 
Olive oil ... . 
0-9130 
1-547-2 
Tin. 
7-2910 
1-5410 Richmann. 
Zink. 
6-8620 
1-5455 Humboldt. 
Oxyd of lead . . 
8-9400 
1-6474 
Antimony . . . 
6-86oo 
1-6952 
Alcohol .... 
o-8i 50 
2*0379 
Lintleed oil . . . 
09280 
2*04I2 
Pitcoal .... 
1*5000 
2-4003 Humboldt. 
Mercury .... 
iV 5 8o ° 
1-9700 Mayer. 
Lead ..... 
u '4459 
0-3138 Richmann. 
Bifmuth .... 
98610 
2-3584 Humboldt. 
E {fence of turpentine 
0*7920 
2-67 52 
Sulphur .... 
I'Sooo 
3-0358 Humboldt. 
Ice. 
0-9160 
1*21 30 
Mercury .... 
13-5800 
3-1948 Tliompfon. 
II. The capacities of bodies for caloric have been fuc- 
cefsfully inveftigated by a variety of chemifts. The fol¬ 
lowing table exhibits the principal conclufions refulting 
from thofie experiments. But it is necefiary, in the firlt 
place, to explain, what is meant by the permanence of 
S T R Y. 
the capacities of bodies for caloric. The capacity of a 
body for caloric is faid to be permanent , while the fame 
quantity of caloric that has railed its temperature any 
given number of degrees, continues to be fufficient to 
raife its temperature an equal number of degrees. The 
capacity of a body for caloric is faid, on the contrary, to 
increafe, when more caloric is required to raife it a cer¬ 
tain number of degrees than was required to raife it an 
equal number of degrees, when it had a different tempe¬ 
rature ; and the capacity is faid to decreafe, when lefs 
caloric is required for that purpofe. Dr. Crawford has 
made a variety of experiments on this fubjedt. He found 
that the capacity of water is permanent from the freezing 
to the boiling point; and afterwards, making ufe of wa¬ 
ter as a ftandard, he tried fimilar experiment with molt 
of the metals and metallic oxyds. The general refult 
of thefe experiments tended to prove, that the capaci¬ 
ties of bodies, while they retain the fame form, are not 
liable to be varied by a change of temperature. This 
conclufion is corroborated by the uniformity of the law 
which bodies obferve in parting with caloric, when they 
are placed in a temperature inferior to their own. This 
law, firfi invefiigated by Sir Ilaac Newton, and fince cor- 
redted and tried experimentally by Martine and MufT- 
chfenbrock, fliovvs, from its application to the cooling of 
different bodies, that the capacities of thefe bodies are 
either permanent, or, if they change, that the changes 
are precifely fimilar in all of them. 
But thefe experiments embrace only a fmall number 
of natural bodies; and Dr. Crawford’s in particular were 
neceflarily confined to a mere point in the fcale of tem¬ 
perature. It is, therefore, departing from the ft rift lie fs 
of induction to conclude, as Dr. Crawford has done, 
that the capacities of all bodies are permanent at all 
temperatures, provided they do not change their -form. 
We have, indeed, the molt complete proof that this 
principle is riot to be received-without many limitations. 
The capacity of air is increafed by mechanically expand¬ 
ing it, and diminifhed by mechanically condenfing it. 
(Pidtet fur le Fen, and Darwin’s Frigoric Experiments on 
the Mechanical Expanfion of Air, Philofophical Tranfac- 
tions for 1788.) Mr.Wedgwood’s clay thermometer has 
its capacity for caloric diminifhed one-third, when burnt 
to 120° of his fcale; and as it loles in weight, during 
this operation, little more than two grains on a pound, 
while its volume is reduced one-half, the diminution of 
capacity rauft be attributed to its condenfation. Thefe 
fadts prove decifively that the capacity of a body may be 
changed without any change of form ; and the free ca¬ 
loric evolved from fo many bodies by fridtion and attri¬ 
tion, while its produdtion is iiluftrated by thefe obfer- 
vations, ferves at the fame time to multiply the examples 
of a change in the capacity of bodies without a change 
in their form. See Wedgwood’s Paper on the Light pro¬ 
duced by Attrition, Philofophical Tranfadtions for 1792. 
It is proper to mention, that Lavoifier and La Place, in 
their Memoires fur la Chaleur, had called inqueltion, upon 
very plaufible grounds, the fuppoied permanence of the ca¬ 
pacities. Reafoning from the known effedts of fufion and 
evaporation upon the capacities, they fuggefted, as ex¬ 
tremely probable, that the capacities would alfo vary 
with the degree of dilatation, and poffibly according to 
a different law for every different body. Subfequent ob- 
fervations feem to juftify their conjedture with refpedt to 
many bodies at lead. 
TABLE OF CAPACITIES. 
Authorities. 
Hydrogen gas. -4000 Crawford, 
Oxygen gas.4-7490 
Atmolpheric air.1-7900 
Steam or aqueous vapour .... 1 5500 
Carbonic acid gas..1- 4.54. 
Arterial blood . ..1-0300 
Water 
