3902.] 
order to write again, on the fame parch- 
ments, church books, and treatifes of 
theology. 
The refearches of Cit. Mongey are ter- 
minated by the collation of fome antient 
texis, whcre mention is made of feeds of 
torrified hemp, by the fmoke of which cer- 
tain barbarous nations were wont to intox- 
icate themfelves—=the fame feeds as they 
now chew, with the fame defign, in fome 
parts of Afia and Europe. 
MANCHESTER LITERARY AND PHILO- 
SOPHICAL SOCIETY. 
In Mr. Joun Datton’s apparently 
very accurate experiments and obferva- 
tions on the power of fluids to conduét 
heat, with reference to Count Rumford’s 
theory on the fubject, we find feveral 
things deferving the attention of the natu- 
ral philofopher. 
Mr, Dalton found that water is of the 
ereateft denfity at 424° Fahrenheit’s ther- 
mometer :—that from 41° to 40° the va- 
riation is fo {mall as to be barely percepti- 
ble on the fcale:—but that, above and 
below thofe degrees, the expanfion has 
an increafing ratio, and at 32° it amounts 
to 160th part cf the whole expanfion from 
424 to 212. . He alfo found that the ex- 
panfion of water was the fame for any 
number of degrees from the point of 
greateft condenfation, whether above or 
below that point; thus at 32° the den- 
fity was the fame as at 53°, the one 
being 104 below, the other roi above 
‘the point of the great denfity. 
Count Rumford infers, that water, and 
other fluids, do not tranfmit heat in the 
manner that folids do, but circulate it 
folely by the internal motion of their par- 
ticles. Mr, Dalton admits the exifence 
of this internal motion, but proves, by a 
number of ingenious and well-conceived 
experiments, that water 1s a conduétor of 
heat ;—-that other fluids conduét it, and 
that they communicate it one to another. 
He acknowledges, however, that water 
is a bad conduétor of heat, and that in an 
experiment, in which hot and cold water 
are ufzd, a flight agitation, for a fingle 
fecond, will do as much to induce the 
equilibrium, as ftanding (till an hour. 
He farther fays, that in the courle of his 
experiments he has known water half an‘ 
inch deeper to differ 50° in temperature 
' from the incumbent water. On the whole, 
he concludes, that the guick circulation 
of heat in water over the fire, &c. is prinz- 
cipally, but not wwhelly, owing to the ime | 
Mon tuiy Maga. No. gt. 
Proceedings of Learned Societies. 
133 
ternal motion excited by an alteration in 
the {pecific gravity. - . 
* From other experiments made by the 
fame ingenious gentleman, on heat and 
cold, produced by the mechanical cone. 
denfation and rarefaction of air, he infers, 
with Meflrs. Lambert, Sauffure, and 
Piet, that a vacuum has its proper ca- 
pacity for heat, the fame 4s air, or any 
other fubftance ; and that the capacity of 
a vacuum for heat is J/efs than that of 
an equal volume of atmofpherical air ; 
alfo that the denfer the air is, the fs is 
its capacity for heat; and upon thele 
principles, he conceives, the phenomena 
are eafily referable to that clafs of chemi- 
cal faéts in which heat and cold are gene- 
rated by the mixture of two different 
bodies. 3 
According to Mr. Dalton’s firft Effay 
on the Conftitution of Mixed Gaffes, &c. 
it appears that the atmofphere is chiefly . 
compofed of four diftinét elaftic fluids, in- 
dependent of one another:—viz. the 
azolic, which is the largeft and mol 
cenfe of all, and which fupports the mer- 
cury in the barometer at a medium of 
21.2 inches:—the oxygenous, the preflure 
of which is about 7.8 inches at a me- 
dium :—the aqueous vapour, which is va- 
riable, according to the temperature: in 
the torrid zone its preflure varies in force 
from 0.6 inch to s.0 inch of mercury 5 
in this climate it is feldom more than 
0.6, and in winter it is often as low as 
0.1 of an inch of mercury: the carbonic 
acid has not been accurately aicertained, 
but may amount too.5 of an inch. Be- 
’ fides thefe four, there is the sydrogenous 
atmofphere, which is very fimall, and hag 
never yet been appreciated ;. and probably - 
in the higher regions, a ferruginous fluid 
that poflefles magnetic properties. 
The object of the fecond Eflay is to de- 
termine the force of fteam from water 
and various other liquids, in diiferent 
temperatures. The refult of Mr. Dal- 
ton’s many experiments on this fubjeét 
can be had only from the tables which he 
has given. ‘ 
In his Effay on Evaporation he has at- 
tempted to determine the effect that a va- 
riation of temperature has upon the quan- 
tity evaporated:—-the ratio of evapora- 
bility of different fluids :—to find a rule by 
which the quantity and effe& of the pre-~ 
vious humidity in the air may be afcer- 
tained, and thereby to obtain a true theory 
of evaporation. 
From the fourth Eflay on the Expan. 
fion of Elafiic Fluids by Heat, Mr. Dal- 
ten is willing to conclude, ‘that all 
U elaftig 
