I c 
liquors or pure efle'nceS, he found that.the cold produced 
by their evaporation was generally fome 7 intermediate 
degree between that produced by water and the fpirit of 
wine. Oilof turpentine funk the mercury three degrees; 
but olive-oil and others, which evaporate very (lowly, or 
not at all, did not fenfibly affeCt the thermometer.. 
To obferve how much the evaporation of fpirit of 
wine, and confequently the cold produced by it^ would 
be inqreafed by eleCtricity, he put the tube containing it 
into an infulating handle, and connected it with the con¬ 
ductor of an eleCtrical machine, which was kept in aftion 
during the time of making the experiment; by which 
means one degree of cold Teemed to be gained, as the 
mercury now funk to 47 0 inltead of 48°, at which it had 
flood formerly. On trying the three mineral acids, he 
found that they heated the thermometer inftead of cooling 
it,- which effeCt he attributes to the heat they themfelves 
acquired by uniting with the moifture of the atmofphere. 
The vitriolic acid, which w'as very ltrongand tranfparent, 
raifed the mercury to 102 0 , the fmoking nitrous acid to 
yz°, and the marine to 66°. 
The apparatus for ufing the lead poffible quantity of 
ether for freezing water, confifts in a glafs tube termi¬ 
nating in a capillary aperture, which is to he fixed upon 
the bottle containing the ether. 'Round the lower part 
of the neck fome thread is wound, in order to let it fit 
the neck of the bottle. When the experiment is to be 
made, the Hopper of the bottle containing the ether is to 
be removed, and the tube juft mentioned put in its room. 
The thread round the tube ought alfo to be previoufly 
moiftened with water or fpittle before it is put into the 
neck of the bottle, in order the more effeClually to pre¬ 
vent the efcape of the ether betwixt the neck of the phial 
and tube. Holding then the bottle by its bottom, and 
keeping it inclined, the fmall dream of ether ilfuing out of 
the aperture of the tube, is directed upon the ball of the 
thermometer, or upon a tube containing water or other li¬ 
quor that is required to be congealed. As ether is very vo¬ 
latile, and has the remarkable property of increafing the bulk 
of air, there is no aperture requifite to allow the air to enter 
the bottle while the liquid flows out. The heat of the 
hand is more than fuflicient to force out the ether in a 
continued ftream. In this manner, throwing the ftream 
of ether upon the ball of a thermometer in fuch a quan¬ 
tity that a drop might now and then, every ten leconds 
for inftance, fall from the bulb of the thermometer, Mr. 
Cavallo brought the mercury down to 3 0 , or 29° below 
the freezing point, when the atmofphere was lomewhat 
hotter than temperate. When the ether is very good, 
I. e. capable of diffolving elaftic gum, and has a fmall 
bulb, not above twenty drops of it are required to pro¬ 
duce this effeCl, and about two minutes of time; but the 
common fort muft be ul’ed in greater quantity, and for a 
longer time; though at laft the thermometer is brought 
down by this very nearly as low as by the bell fort. 
To freeze water by the evaporation of ether, Mr. Ca¬ 
vallo took a thin glafs tube about four indies long, and 
one-fifth of an inch diameter, hermetically fealed at one 
end, with a little water in it, fo as to take up about half 
an inch of the cavity. Into this tube a (lender wire was in¬ 
troduced, the lower extremity of which was twilled into a 
fpiral, and ferved to draw up the bit of ice when formed. 
He then held the glafs tube by its upper part with the 
fingers of the left hand, and kept it continually and 
gently turning round its axis, firft one way and then the 
other; whilll with the right hand he held the phial con¬ 
taining the ether in fuch a manner as to direfl the ftream 
on the outfide of the tube, and a little above the furface 
of the water .contained in it. The capillary aperture 
Ihould belcept almolt in contaCl with the furface of the 
tube containing the water; and by continuing the ope¬ 
ration for two or three minutes, the water will be frozen 
as it were in an inftant. This congelation, however, is 
only fuperficial; in order to congeal the whole quantity 
of water, the operation muft be continued a minute or 
■-Vol. X. No. 707, 
e; „ ?2i 
two longer; after which the wire will be found kept very 
tight by the ioe. The hand muft then be applied to the 
outfide of the tube, in order to fbften the furface of the 
ice; which would otherwile adhere very firmly to the 
glafs; but when this is done, the wire eafiiy- brings,it 
out. ' . 
feometimes oqr author was accuftomed to put' into the 
tube a fmall thermometer iiiflead of the wire, and thus 
he had an opportunity of obfervihg a very curious phe¬ 
nomenon unnoticed by others, viz. that in the winter¬ 
time water requires a fmaller degree of cold to congeal it 
than in the fummer. In the winter, for inftance, the 
water in the tube will freeze when the thermometer 
Hands about 30 0 ; but in the fummer, or even when the 
thermometer {lands at 6o°, the qnickfilver mull be brought 
down 10, 15, or even more, degrees below the freezing- 
point, before any congelation can take piace. In the 
fummer time therefore a greater quantity of ether, and 
more time, will be required to congeal any given quan¬ 
tity of wafer than in winter. When the temperature 
of ,the atmofphere- has been about 40 0 , our author has 
been able to congeal a quantity of water with an 
equal quantity of good ether; but in fummer two or 
three times the quantity are required to perform the 
effect. “ There feems (fays he) to be fomething in the 
air, which, befides heat, interferes with the freezing of 
water, and perhaps' of all fluids; though I cannot-lay 
from my own experience whether the above-mentioned 
difference between the freezing in winter and fummer 
takes place with other fluids, as milk, oils, wines,” See. 
The proportion of ether requifite to congeal water,, 
feems to vary with the quantity of the latter; that is, a 
large quantity of water feems to require a proportionably 
lefs quantity of ether to freeze it than a fmaller one. 
“ In the beginning of the fpring (fays Mr. Cavallo), I 
froze a quarter of an ounce of water with about half an 
ounce of ether; the apparatus being larger, though fimi.. 
lar to that delcribed above. Now as the price of ether, 
fufficiently good for the purpofe, is generally about i8d. 
or 2s. per ounce, it is plain, that with an expence under 
two (hillings, a quarter of an ounce of ice, or ice-cream, 
may be made, in every climate, and at any time, which 
may afford great latisfaClion to thofe perfons, who, living 
in thofe places where no natural ice is to be had, never 
faw or tailed any fuch delicious refrefhment. When a 
fmall piece of ice, for inftance, of about ten grains weight, 
is required, the neceffary apparatus is very fmall, and the 
expence not worth mentioning. I have a fmall box four- 
inches and a half long, two inches broad, and one and a 
half deep, containing all the apparatus neceffary for this 
purpofe, viz. a bottle capable of containing about one 
ounce of ether; two pointed tubes, in cafe one ihould 
break; a tube in which the water is to be frozen, and a 
wire. With the quantity of ether contained in this fmall 
and very portable apparatus, the experiment may be re¬ 
peated about ten times. A perfon who wifhes to per¬ 
form fuch experiments in hot climates, and in places 
where ice is not eafiiy procured, requires only a larger 
bottle of ether befides the whole apparatus deferibed 
above.” Electricity increafes the cold produced by means 
of evaporating ether but very little, though the effeCt is 
perceptible. Having thrown the electrified and alfo the 
uneleCtrifted ftream of ether upon the bulb of a thermo¬ 
meter, the mercury was brought down two degrees lower 
in the former than in the latter cafe. 
The following is the common method of making ice¬ 
cream. Take a lufficient quantity of cream; and, when 
it is to be mixed with rafpberry, or currant, or pine, a 
quarter part as much of the juice or jam as of the cream ; 
after beating and (training the mixture through a cloth, 
put it with a little juice of lemon into the mould, which 
is a pewter veil'd, and varying in fize and fhape at plea- 
fure; cover the mould, and filace it in a pail about two- 
thirds full of ice, into which two handfuls of lalt have 
been thrown; turn the mould by the hand-hold with a 
8 X quick 
