CHEMISTRY. 
slwiiys exceeds, by about an eighth, the quantity of al¬ 
cohol conl'umed during the operation ; whence it appears 
that alcohol contains one of the elements of water, which 
is hydrogen ; and the atmofpheric air furnifties the other, 
which is oxygen. By an experiment fimilar to this, La- 
voilier found that fixteen parts of alcohol furnifhed by 
combuftion from feventeen to eighteen ounces of water. 
An ingenious apparatus for recompofing water by the 
combuftion of hydrogen gas in oxygen gas, has lately 
been invented by Mr. Cuthbertfpn, and is evidently an 
improvement upon that of Lavoifier. The letters ABCD, 
at fig. 4, in the laft-mentioned plate, reprefent the in¬ 
ftrument; and abcff Ihew the veflel to which it is af¬ 
fixed. The glafs balloon AD, which may contain 1000 
cubic inches of water, has a brafs-cap which fcrews off 
at the top, and is perforated at the botto* 5 > ? fai which the 
piece e f (fig. 5.) is fere wed. B and C are two glals re¬ 
ceivers, with proper mountings, the tops of which pafs 
through EF, a ftraight bar of brafis, are made faft to the 
bar by female fcrews put on thefe tops, which are per¬ 
forated perpendicularly, and have alio a fide-hole cor- 
refponding with a hole in the brafs-bar and with two 
holes in ef communicating with the large bottle. At m 
and n are two lion-cocks in the brals-bar, to fhut or 
open the communication between the receivers and the 
bottle. FR and EN are two flat pieces of brafs made' 
faft to the veflel containing the receivers, and which is 
nearly filled with water, by means of fcrews at a and b. 
O, a metallic wire, made faft to the brafs cap at A : the 
lower part of this wire is made of platina, and is brought 
as near as poflible to the piece ef, but not to touch it. 
When the inftrument is to be ufed, the ftop-cocks being 
kept fhut, the large veflel mull be detached from the re¬ 
ceivers, by unferewing the female fcrews Cf_Q, filled with 
oxygen gas by any of the common methods, and again 
put in its place. The receiver B, which has a hole in its 
fide at 0, mull then be filled with oxygen gas, and C with 
hydrogen; and, while electric fparks are made to pafs 
from the wire O to the aperture e, the qock n mult be 
opened, by degrees, till the gas takes fire. Stop the 
eleftric fparks and regulate the flame by turning the 
cock one way or the other. The cock m , which fupplies 
the oxygen gas, mu ft be kept quite open, and the re¬ 
ceivers be kept fupplied, C to its lip and B to the hole 
o, by known meafures of the gafes, from time to time, 
while the procefs is continued. The paflage that leads 
from the hydrogen ghs to the large veflel is made fmaller 
than that from the oxygen, that the gas may enter in a 
very fmall ftream. The hole in the fide of the receiver B 
is for the purpofe of preventing more oxygen gas being in-* 
trodyced than will fill it to that point, that the column 
of water may always be heavier upon the hydrogen gas, 
which has to force its way through a fmaller aperture 
than the oxygen gas. The fame end would be gained 
by making B only about half the depth of C. Both thefe 
receivers are open below, to receive the gas introduced 
under them. Several other inftruments for the recom- 
pofition of water lrave been lately projected ; but as they 
do not feem to poflefs any advantages over thofe we have 
mentioned, it were fuperfluous to delcribe them here. 
The folubility of water in air is a fact highly deferring 
the attention of chemifts, as this circumftance may often 
occafion confiderable variations in the refult of experi¬ 
ments which require great degrees of accuracy. The 
property of abforbing water does not feem to be confined 
to atmofpherical air, but to be common to molt, if not 
all, bodies capable of affuming the elaltic form. Our 
knowledge of this fubjeft is, how'ever, at prefent ex¬ 
tremely limited ; nor has it hitherto obtained that atten¬ 
tion which its importance demands. Sauffure relates 
fome experiments which prove the folubility of w'ater in 
.hydrogenous gas, and in carbonic acid gas; but he has 
omitted to mention the quantity thefe fluids are capable 
ct diflolving. Dr. Hutton has made a very happy appli¬ 
cation of our knowledge of this fubjeft: to explain the 
Vo 1.. IV. No. 190. 
209 
produftion of rain. The diflolving power of the air, he 
oblerves, muff be either in the fame ratio with the in- 
creale of temperature, or it muft be in a lefs or in a greater 
ratio. If in the fame ratio, the temperature of two equal 
portions of air, faturated with water, and mixed together, 
at different temperatures, will be found to be the arith¬ 
metical mean between the extreme temperatures; fo 
there will be no precipitation of water. If in a left ra¬ 
tio, then it is evident that the mixtures of two portions 
of fatuiated air, at different temperatures, will produce 
no condenfation of water; but, on the contrary, wili be 
capable of diflolving an additional quantity of that fluid. 
If in a greater ratio, the mixture of the two faturated 
portions of air will produce a condenfation of water. It 
is this laft cafe only that can be applied to explain the 
phenomena of vapour, and the formation of rain. Ac¬ 
cording to this hypothefis, therefore, whenever two ftreams 
of air, or two contrary winds, of different temperatures, 
meet together, vapour or rain muft neceflarily be pro¬ 
duced. For the numerous fails in proof of this inge¬ 
nious theory, fee D-iffertations on different Subjefls of Natu¬ 
ral PhiioJ'ophy. 
Count Rumford, lately fir B. Thompfon, has made a 
Angular difeovery with refpeft to the non-condufting 
power of water for caloric. It had always been fuppofed 
that caloric was diffufea in all direftions through water 
in precifeiy the fame manner as through folids of every 
kind. From a feries, however, of ingenioully-contrived 
experiments, this philofoplier has been led to infer, that 
although the particles of water receive caloric from other 
bodies, and communicate it to them again, yet that 
among the particles of this fluid themfelves no commu¬ 
nication ofcaloric whatever takes place. Caloric, according 
to him, is diffuledin waterfolely by the motion of thofe par¬ 
ticles which have had their lpecific gravity increaled ordi- 
miniftied in confequence of a change in the ftate of their 
temperature. This diffufion, therefore, may be obllruft- 
ed, either by dimihifhing the fluidity of water, or by 
mixing with it fubftances that mechanically retard the 
motion of its particles. The effeft of thele caufes he has 
evinced by a number of comparative experiments. Ac¬ 
cidentally perceiving the motion of iome fine particles of 
duft in a ipirit of Wine thermometer, this philofopher 
was led to contrive the means of exhibiting to view thole 
internal motions of the particles of water which accom¬ 
pany every change in the ftate of its temperature. To 
render this motion vifible, he mixed a Imall quantity of 
amber, finely pulverized, with water, the lpecific gravity 
of which had been raifed to the fame ftandard by the ad¬ 
dition of an alkaline fait. On plunging a glals globe, 
with alongcylindrical neck, containing this mixture, into 
boiling water, fome very interefting phenomena were ob- 
lerved. Two currents, in oppolite directions, began at 
the fame inftant to move with great celerity in the liquid in 
the cylindrical tube; the afeending current occupying 
the fides of the tube, while that which moved down¬ 
wards occupied its axis. As the faline liquor grew 
warm, the velocity of thefe currents gradually diminilh- 
ed ; and at length, when the liquor had acquired the 
temperature of the furrounding water in the jar, thefe 
motions ceafed entirely. On taking the glafs body out 
of the hot vs'ater, the internal motions of the liquor re¬ 
commenced, but the currents had changed their direc¬ 
tions; that which, occupied the axis of the tube being 
now the afeending current,' When the contents of the 
glafs body had acquired th,e temperature of the air of the 
room, thefe motions ceafed ; but they immediately re¬ 
commenced on expofmg the inftrument to any change 
of temperature. The motions in oppolite direftions in 
the liquid in the tube were exceedingly rapid on the hid¬ 
den application of a ftrong heat, and afforded a very en¬ 
tertaining fight: but to a fci,entific obferver they were 
much more than amufing; they detefted nature, as it 
were, in the very aft, in one of her molt hidden opera¬ 
tions, and rendered motions vifible in the midft of an 
3 H ‘ iiivilibje 
