MECHANIC S. 
with a conftant additional weight in the upper bafin, or 
whether the effeft of this weight be produced by the ad¬ 
ditional piece in the lower dilh. From this explanation 
there will be no difficulty in feeing how this inftrument 
may be adapted to every cafe in praftice. 
It may be ufed, r. for folids. It differs not in this re¬ 
flect from Nicholfon’s hydrometer. The only condition 
will be, as in this inftrument, that the abfolute weight of 
the body to be examined fhali be rather lefs than the con- 
fiant additional weight, which in this inftrument is 5 
grammes, or 115 grains'. 
2. For liquids of lefs fpecific gravity than water, the in¬ 
ftrument, without the additional weight above mentioned, 
weighs about 2 decagrammes, (459 grains,) in the dimen- 
fions before laid down. It would he eafy to limit its 
weight to the utmoft accuracy. We have therefore the 
range of one-fifth of buoyancy, and confequently the 
means of alcertaining all the intermediate denfities from 
water to the molt highly rectified fpirit of wine, which is 
known to bear in this refpeft the ratio of 8 to jo with re¬ 
gard to water. 
3. When liquids of greater fpecific gravity than water 
are to be tried, the conftant weight being applied below, 
by means of the additional piece, which weighs about 6 
grammes (138 grains), the inftrument can receive in the 
upper bafin more than 4 times the ufual additional weight, 
without lofing the equilibrium of its vertical polition. 
In this ftate it is. capable of (bowing the fpecific gravity 
of the molt concentrated acids. 
4. It pofiefies another property common to Micholfon’s 
inftrument, namely, that it may be ufed as a balance to 
determine the abfolute weight of fuch bodies as do not 
exceed its additional load. 
5. Laftly, the purity of the water being known, it will 
indicate the degrees of rarefaction and condenfation in 
proportion to its own biuk. 
This inftrument may be readily conftrufted by any work¬ 
man in glafs. The additional piece for the lower bafin 
will require fome attention to make it perfectly agree with 
£he conftant upper weight, as to the immerfion of the in- 
iirument. But this objeft may, by careful adjuftment, 
be afcertained with the utmoft certainty and accuracy. 
The bulb of glafs is for this purpofe drawn out to a fine 
point; a fuflicient quantity of mercury is then introduced 
to fink it, and the aperture clofed with a little piece of wax. 
The bulb being then placed in the lower bafin of the in- 
Itrument, the upper bafin is to be loaded until the mark 
on the ftem becomes accurately coincident with the fur- 
face of the water. The fum of the weights added above 
is precifely equal to that of the quantity of mercury ne- 
ceflary to be added to that in the glafs bulb; which done, 
nothing more is needed than to leal the point by fufion, 
taking care not to change its bulk. The whole is ren¬ 
dered portable by means of a cafe in which all the delicate 
parts arefecured from preflure, and the heavier parts fup- 
ported in fuch a manner as to refill the excels of motion 
they are capable of acquiring by virtue of their trials. 
This laft circumftance is frequently overlooked by fuch 
workmen as are employed in the package of inftruments ; 
'whence it neceflarily follows, that fome ft rain, of fracture 
inuft be produced when matters of very unequal,deniity 
are expofed to receive a common impulfe. 
To find the fpecific gravity of any folid by the gravi¬ 
meter, -obferve this rule: “From tiie weight in the up¬ 
per difh, when .the inftrument is properly immerfed in the 
unknown fluid, take the weight which is placed with the 
'body in the fame fcale at the like adjuftment. The re¬ 
mainder is the abfolute weight of the folid. Multiply this 
by the fpecific gravity of the fluid, and referve the pro- 
■dudi. From the additional weight when the body is placed 
in the lower bafin, take the weight when it was placed in 
the upper. The remainder will be the lofs of weight by 
immerfion. Divide rite reserved product by the lofs by 
immerfion, and the quotient will be the fpecific gravity 
of the folid with regard to diftilled water at the standard 
temperature and preflure.” 
VOL. XIV. Flo. 1007. 
703 
To find the fpecific gravity of a fluid proceed thus ^ 
“ To the weight of the gravimeter add the weight re¬ 
quired in the upper bafin to fink it in the unknown fluid. 
Again, to the weight of the gravimeter add the weight 
required in the fame manner to fink it in the diftilled 
water. Divide the firft fum by the latter; and the quo¬ 
tient will be the fpecific gravity of the fluid in quef- 
tion.” 
Mr. Snart, of Tooley-ffreet, optician, has invented and 
furnifhed us with a defeription and drawings of a Chemical 
Aerometer , for afeertaining the fpecific gravity and vulgar 
weight of all fluids heavier than water, by one operation. 
Tile inftrument is perfectly novel, and appears to us to 
fuperfede all others, in facility, as well as ufefulnefs. Tt 
begins at rain water, whole fpecific gravity is i*oooo ; and 
goes on to the moft highly concentrated fulphuric acid, 
Sp. Gr. 2* 1232. He has alfo written a pamphlet (to ac¬ 
company the inftrument)', which contains a Table of Spe¬ 
cific Gravities,fo contrived, that, by repeatedly reiterating 
the fame decimal fractions from the digits and divifions, 
(as found in an auxiliary Table,) no lefs than 7040 fpe¬ 
cific gravities and'vulgar weights are fhown in the fame 
fpace as would naturally have been occupied by only 46 of 
each, without crowding or the leaft ambiguity (a power 
of concentration of 150 times) ; and, as the Table has re¬ 
ference to real quantity , the greateft labour and accuracy 
have been ufed to afeertain the true cubic content of that 
ftandard nieafure to which it refers, viz. the Winchejler gal¬ 
lon mtafure in the Exchequer: which is the fruftum of a 
cone made in 1601, whole greateft or top diameter is 6f 
■£% inches, leaft or bottom diameter 5J;, angular or flant fide 
gjj-, perpendicular depth 9J, A-, and the product of whole 
cubic dimenfion is therefore 278*1669087879322265625 
cubic inches, inftead of 282, as generally received, and 
which error has exifted in the world 215 years. How¬ 
ever, the public having the dimenfions may now fatisfy 
themfelves; and we hope fir G. Clerk’s bill will let all to 
rights. 
Inftruments bearing the fame name, have been made 
from time immemorial; but this, as the author deferibes 
it, being conftructed by the law's of geometry, or rather 
of ftereometry, the fcale is not only augmented tenfold, 
and anfwers two queltions at once, but is alfo fo unequi¬ 
vocally definite and plain, that it cannot be miftaken or 
doubted by-any one, as whatever degree the inftrument 
finks to in the fluid, is the fpecific gravity and vulgar 
weight of that fluid ; and the numbers on the ftem or 
fcale are not arbitrary, but real weights, with their true 
fpecific gravities oppofite, and on the fame line. 
As the difference between unindurated water and con¬ 
centrated fulphuric acid is very great, the number of de¬ 
grees and fpecific gravities inuft be proportionate. The 
barrel, or thirty-fix gallons, of water, weighing only 3621b. 
(Sp. Gr. roooo.) while concentrated fulphuric acid weighs 
76951b. (Sp. Gr. 2*1252.) it was therefore impoflible to 
produce all thefe variations on one ftem of the inftru- 
ment, without weights; and weights of the requisite fize 
and materials, (viz. of glafs, gold, or platinum,) for fie r 
reometric or pecuniary reafons, were inadmifiible ; th,« 
inventor has therefore judicioufly divided his fcale into 
two inftruments; the laft commencing about where tha 
firft left oft, leaving however a few degrees on each to 
fpare. Thus, if the inftrument fig. 15, Plate XIX, goes 
to 502ib. (Sp. Gr. 1-3868 ) then fig. 16 begins at 492, and 
goes on to 76911b. (Sp. Gr. 2*1252.) The two inftru- 
ments, comprehending ail the differences from the loweft 
to the higheft poflible degree of impregnation, or to which 
fluids can be faturated ; and Ihowing how much mineral, 
vegetable, alkaline, acetous, faccharine, faline, or other, 
matter, may be held in permanent folution in fuch fluid. 
The firft column of figures in'each inftrument (hows 
the vulgar weight of 36 gallons, or a barrel, of the fluid, 
whatever it may be, beginning with rain-wafer, the lighted, 
of which the weight is 362 lbs. to the barrel; and pro¬ 
ceeding to highly-concentrated fulphuric acid, the heavieft 
of all fluids (mercury excepted), of which the weight of 
