890 
A variety from Derbyshire, in minute 
pale yellow crystals, consisted of 
Carbonicacid - - 34.8 
Oxyd of zinc - - 68.2 
100.0 
The electric calamine of Regbania, in 
Hungary, afforded, - 
Quartz - - - - 25.0 
Oxyd of zine - - 68.3 
Water -%+'+ - (4.4 
97.7 
Loss - - - - - 2.3 
00.6 
Tt deserves to be noticed, that the 
quartz, though in so large a proportion, 
was rendered soluble by means of the 
‘metallic oxyd in dilute sulphuric acid, as 
after a time the solution became gelati- 
nous. 
&. Experiments on the Quantity of Gasses ab- 
sorbed Ly Water at different Temperatures 
‘and under different Pressures. By Mr. 
W. Henry. 10. Appendix to ditto. 
The first section of this paper relates 
to the absorption of gasses by water, 
under the usual atmospheric pressure. 
In this Mr, Henry has observed, that the 
proportion of carbonic acid gas absorbed 
by water, by means of agitation, depends 
greatly on the purity of the gas made 
mse of. 'Fhus when at the temperature 
of 55°, 20 measures of carbonic acid are 
agitated with ten of water, at least half 
the gas is absorbed; but from a mixture 
of YO measures of carbonic acid with 10 
of atmospheric air, 10 parts of water take 
ap only 6 of carbonic acid. The cause 
.of this diminished absorption is merely 
stated. to be “connected with the pro- 
portion of common air contained in the 
unabsorbed residuum.” Undoubtedly it 
is; but surely we may make a nearer 
approach to the true reason of the fact 
by supposing that a partition of the car-, 
bonic acid between the water and air 
takes place in the compound ratio of 
their respectiye quantities and chemical 
w{Hnities ; whereas, when pure carbonic 
acid is employed, the water unites with 
the acid to perfect saturation, on account 
of the absence of antagonist affinities. 
But Mr. Henry is disposed to believe, 
with Mr. Dalton, that the ‘¢absorption 
of gasses by water is purely a mechanical 
effect,”? a supposition, in our opinion, 
very incapable of accounting for many 
well-known facts. Common air cannot 
GENERAL SCIENCE. 
be entirely expelled from water by long 
boiling and the action of the air-pump, 
but if water having been so treated is 
impregnated with pure carbonic acid, 
the small quantity of air contained in the 
water will be liberated, obviously on ac- 
count of its affinity with the water being 
overcome by that of the carbonic acid. 
The second section of Mr. Henry’s pa- 
per treats of the influence of pressure in 
promoting the absorption of gasses, and 
presents us with the following very im- 
portant general law, deduced from a 
series of fifty experiments on various 
gasses, that ‘‘ under equal circumstances 
of temperature water ‘takes up, in all 
cases, the same volume of condensed gas 
as of gas under ordinary pressure.” 
4. Experiments and Qlservations en the va- 
rious Alloys, on the specific Gravity, and 
on the comparative Wear of Gold; being 
the Substance of a Report made to the Right 
Honourable the Lords of the Committee of 
Privy Council, appointed to take into Con- 
sideration the State of the Coins of this 
Kingdom, and the present Establishment 
and Constitulion of his Majesty's Mint. 
By Cuarves Harcuerr, Esq, ERAS. - 
This highly interesting paper is the 
joint production of Mr. Hatchett and 
Mr. Cavendish, and will be found, in all 
respects, worthy of the high reputation 
and acknowledged abilities of these phi- 
losophers. The experiments were un- 
dertaken at the desire of the privy coun- 
cil, in consequence of a considerable loss 
which the gold coin appeared to have 
sustained by wear within certain periods, 
which induced them to have an inquiry 
instituted, in order to ascertain whether 
this loss was occasioned by any defect.in 
the quality, or figure, or impression of 
the coins. 
The subject naturally divides itself 
into an enquiry concerning the effects 
produced upon gold by various metals 
when alloyed with it in different propor- 
tions; concerning the specific gravity of 
gold variously alloyed, and the modifi- 
cations to which it is liable; and cons 
cerning the effects of friction in various 
circumstances. These are made the sub- - 
jects of three sections, which we shall 
proceed to give some account of. 
First, Of the effects produced upon 
gold by combination with other metals. 
Arsenic, though it is. with difheulty 
united with gold when the two sub- 
stances are in small quantity and mixed 
in an open crucible, yet combines easily 
with this meta) when applied to it at @ 
