I 
F R E 
particles that are the chief caufe of freezing are faline, 
mixed in a due proportion, congelation bearing a 
near relation to cryftallization. 
This fait is fuppofed to be of the -nitrous kind, and 
to be fumifhed by the air, which is generally found 
/to abound in nitre. 
It is indeed no difficult matter, to account for the 
particles of nitre preventing the fluidity of water. 
Thefe particles are fuppofed to be fq many rigid 
pointed fpicula, which are eaflly impelled or driven 
into the ftamina or globules of water ; which, by this 
means, becoming varioufly mingled and entangled 
with it, do, by degrees, weaken and deftroy the mo- 
tion of it. 
The reafon that this effeift arifes only in fevere win- 
ter weather, is, that it is then only that the retrading 
adion of the nitrous fpicula is more than equal to the 
power or principle by which the fluid is otherwife 
kept in motion, or difpofed for motion. 
Several experiments of artificial freezing fupport this 
opinion. 
For if you mix a quantity of common faltpetre with 
fnow, or ice pulverized, and diffolve the mixture in 
the fire, and then im merge a tube full of water in the 
folution ; the water, that part of it next the mixture, 
will freeze prefently, even in a warm air. 
Whence they argue, that the fpicula of the fait are 
driven through the pores of the glafs, and mixed with 
the water, by the gravity of the mixture, and of the 
incumbent air •, for that it is evident, that the fait 
has this effed, inafmuch as it is certainly known, that 
the particles of water cannot find their way through 
the pores of the glafs. 
In thefe artificial freezings, in whatever part the 
mixture is applied, there is prefently a fkin or lamina 
of ice produced, whether at the top, bottom, or fides, 
by reafon that there is always a flock of faline cor- 
pufcles, fufficient to overpower the particles of fire ; 
but natural congelations are confined to the top of 
the water, where the laft moft abounds. 
But this fyftem is oppofed by the author of the Nou- 
velle Conjedure pour expliquer la Nature de la Glace, 
who objeds, that it does not appear, that the nitre 
always enters the compofition of ice ; but if it did, it 
would fall fhort of accounting for fome of the princi- 
pal effeds •, as, 
How fhould the particles of nitre, by entering the 
pores of the water, and fixing the parts, caufe the 
water to dilate, and render it fpecifically lighter ? 
They fhould naturally augment its weight. 
This and fome other difficulties, fhew the neceffity 
of a new theory ; and therefore the ingenious author 
advances this which follows, which feems to foive the 
phenomena in a manner that is more eafy and fimple, 
as not depending upon the admiffion or extrufion of 
any heterogeneous matter. 
The water freezes in the winter only, becaufe its parts, 
then being more clofely joined together, mutually 
embarrafs one another, and lofe all the motion they 
had ; and that the air, or rather an alteration in the 
1 bring and force of the air, is the caufe of this clofer 
union' of water. 
It is evident from experiment, that there are an in- 
finite number of particles of grofs air mterfperfed 
•among the globules ot water j and it is allowed, tnat 
each particle of air has the virtue of a fpring V and 
hence this author argues, that the fmali firings of 
grofs air, mixed with water, have more force in cold 
winter weather, and do then unbend themfelves 
more, than at other times. Hence thofe fprings thus 
unbending themfelves on one fide, and the external air 
continuing to . prefs the furface of the water on the 
other, the particles of the water, being thus con- 
itringed land locked up together, muft lofe their mo- 
tion and fluidity, and form a hard,- confident body, 
till a relaxation of the fpring of the air, from an 
increafe of heat, reduce the particles to their old 
dimenfions, and leave room for the globules to flow 
again. 
But this fyftem feems to be built upon a falfe prin- 
F R E 
triple, for the fpring or elafticity of the air is not ia- 
creafed by cold, but diminiflied ; air condenfes by 
cold, and expands itfelf by heat *, and it is. demon- 
ilrable in pneumatics, that the elaftic force of ex- 
panded air is to that of the fame air condenfed, as 
the bulk when rarefied is to its bulk when condenfed. 
Indeed, fome authors, in order to account for the 
increafe of the bulk and dimenfion of the fpecific gra- 
vity of frozen water, have advanced as follows, viz. 
That the aqueous particles, in their natural date, were 
nearly cubes, and fo filled their fpace without the in- 
terpofition of many pores •, but that they are changed 
from cubes to fpheres, by congelation ; from whence 
it will neceffarily follow, that there muft be a great 
deal of empty fpace between them. 
But, in oppofition to this hypothefis, the nature of 
fluidity and firmnefs eaflly fuggefts, that fpherical 
particles are much properer to conftitute a fluid than 
cubical ones, and lefs difpofed to form a fixed than 
cubic one. 
But after all, in order to come to a confident theory' 
of freezing, we muft either have recourfe to the fri- 
gorific matter of the Corpufcularians, confidered un- 
der the new light and advantages of the Newtonian 
philofophy, or to the ethereal matter of the Cartefi- 
ans, under the improvements of Monf. Gauteron. 
The true caufe of freezing, or the congelation of wa- 
ter into ice, fay the former, feems plainly to be the, 
introduction of the frigoriftc particles into the pores 
or interftices between the particles of the water, and 
by that means getting fo near them, as to be juft 
within the fpheres of one another’s attracting force, 
and then they muft cohere into one folid or firm 
body ; but heat afterwards feparatlng them, and put- 
ting them into various motions, breaks this union, 
and feparates the particles fo far -from one another, 
that they get out of the dtftance of the attracting force, 
and into the verge of the repelling force, and then the 
water re-afifumes its fluid form. 
Now, that cold and freezing proceed from fome fub- 
ftance of. a faline nature floating in the air, feems pro- 
bable from hence : 
That all falts, and more eminently fome particular 
ones, do prodigioufly increafe the force and effeds of 
cold, when mixed with fnow or ice. It is alfo evident, 
that all faline bodies produce a ftiffnefs and rigidity 
in the parts of thofe bodies into which they enter. 
It appears, by microfcopical obfervations upon falts, 
that the figure of fome falts, before they fhoot into 
maffes, are thin, double wedged, like particles which 
have abundance of furface, in refped to their foli- 
dity ; and is the reafon why they fwim in water, when 
once raifed in it, though fpecifically heavier. 
Thefe fmali points, getting into the pores of the 
water, whereby they are alio, in fome meafure, fuff 
pended in the winter time, when the heat of the fun 
is not ordinarily ftrong enough, to diffolve the falts 
into a fluid, to break their points, and to keep them 
in perpetual motion, being lefs difturbed, are at more 
liberty to approach one another ; and, by fhoqting 
into cryftals of the form above-mentioned, do, by 
both their extremities, infmuate themfelves into the 
pores of the water, and by that means freeze it into a 
felid form. And it is apparent, that the dimenfions 
of water are increafed by freezing, the particles ot 
it being kept at fome diftance from one another, by 
the intervention of the frigoriftc matter. 
But befides this, there are many little volumes, or 
fmali particles of air, included at feveral diftances, 
both in the pores of the watery particles, and in the 
interftices formed by their fpherical figure! Now, by, 
the infinuation of the cryftals, the volumes of air are 
driven out of the watery particles, and many of them 
uniting, form larger volumes* which thereby have a 
greater force to expand themfelves than when they 
are difperfed ; and id both enlarge the dimenfions, 
and leften the fpecific gravity of water thus congealed 
into ‘ice. 
And hence (fays Dr. Cheyhe,- from whom this laft ac- 
count is taken) we -may guefs at the manner how wa- 
ter. 
