F R E 



particles that are the chief caufe of freezing arc fuline, ' 

 nnxed in a due proportion, congelatioii bearing a 

 mar relation to cryltallization. 



Tliis laic is fuppofed to be of the nitrous kind, and 

 t(» be furniflied by the air, which is generally found 

 to abound in nitre. 



h is indeed no difficult matter, to account for the 

 particles of nitre preventing the fluidity of water. 

 I'hefe particles are fuppofed to be fo many ^ rigid 

 pointed fpicula, which are eafily impelled or driven 

 into the ftamina or globules of water ; v/hich, by this 

 means, beconfing varioufly mingled and entangled 

 with it, do, by degrees, weaken and deftroy the mo- 

 tion of it. 



n^he reafon th.at this eflect arifes only in fevere win- 

 ter weatlier, is, that it is then only that the retracting 

 adion of the nitrous fpiculais more than equal to the 

 p'jwer or principle by which the fluid is otherwifc 

 kept in motion, or difpofed for motion. 

 Several experiments of artthcial freezing fupport this 



opinion. 



For if you mix a quantity of common filtpetre with 



fnow, or ice pulverized, and difTolve the mixture in 



the fire, and then immerge a tube full of v/ater in the 



Iblution •, the water, that part of it next the mixture, 



air. 



will freeze prefently, even in a warm 

 Wlience they argue, that the fpicula of the filt 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 thiselfed:, 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, Vv'hether at the top, bottom, or fides, 

 by reafon that there is always a ftock of faline cor- 

 pufcles, fufRcient to overpower the particles of fire ; 

 but natural congelations are confined to the top of 

 the witer, where the laft moft abounds. - • 

 But thisfyftem isoppofed by the author of the Nou- 

 velle Conjefture pour expliquer la Nature de la Glace, 

 who objects, 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 effefls ; 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 fliould naturally augment its weight. 

 This and fonie other difficulties, flicw the necefllty 

 of a new theory ; and therefore the ingenious author 

 advances this which follows, which feems to folve the 

 pha^nomena 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 

 cmbarrafs one another, and lofe all the motion they 

 had ■, and that the air, or rather an alteration in the 



fpring 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 interfperfed 

 among the globules of water*, and it is allov/ed, that 

 each particle of air has the virtue of a fpring; and 

 , jience this author argues, that the fmall fprings of 

 gi-ofs air, mixed with water, have more force in cold 

 winter weather, arid do then unbend themfelves 

 more, than at other times. Hence thofe fprings thus 



■ unbending themfvilves on one fide, and the external air 

 continuing to prefs the furface of the water on the 

 otlter, the particles of the water, being tlius con- 

 ftringed and locked up together, muft lofe their mo- 



■ tion and fluidity, and form a hard, confifl;ent body, 

 till a relaxation of the fpring of the air, from an 

 increafe of heat, reduce tlie particles to their old 

 dim.cnfions, and leave room for the globules to flow 

 aeain. 



}jut this fyftcm feems to be built upon a falfe prin- 



as 



F R E 



ciple, for the fpi'ing or ^ ^afticity of the air k not » 

 cre.iied by cold, but diniiniflied •, air condenfcs h" 

 cold, and expands itfclf by heat ; and it is demo 

 flrable in pneumatics, that the elatlic force of e 

 panded air is to that of the fame air condenfed 

 the bulk when rarefied is to its bulk when condenfed 

 Indeed, fonie authors, in order to account for t\ 

 increafe of the bulk and dimenfion of the fpccinc rr^ 

 vity of frozen water, have advanced as follows viz 

 That the aqueous particles, in their natural itate,\vcrc 

 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 neceflTarily follow, that there mufl: be a r^reac 

 deal of empty fpace betv/ccn them. 

 But, in oppofition to this hypothefis, the nature of 

 fluidity and firmnefs eafily luggefl:s, tliat fpherical 

 particles are much propcrer to conftitute a fluid thaa 

 cubical ones, and iefs difpofed to form a fixed thsa 

 cubic one. 



But after all, in order to come to a confident theory 

 of freezing, v/e muft cither 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 Cartel 

 ans, under the improvements of Monf Gautcron. 

 The true caufe of freezing, or t!ie congelation of wa- 

 ter into ice, fay the former, feems plainly to be the 

 introduftion of the frigorific particles into the pores 

 or interilices between the particles of the water, and 

 by that means getting fo near them, as to be juil 

 within the fpheres of one another's attracting force, 

 and then they muft cohere into one folid or firm 

 body i but heat afterwards feparating 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 diftance of the attraftingforcCj 

 and into the verge of the repelling force, and then the 

 water re-aflumes its fluid form. .- r. ; : .. u . . -.m 



Now, that cold and freezing proceed from fome fub-_ 

 ftance of a faline nature floating in the air, feems pro- 

 bable from hence : , -. ' i 

 That all falts, and more eminently fome particular 

 ones, do prodigioufly increafe the force andeffedsof 

 cold, when mixed with fnow or ice. It is alfo evident, 

 that all faline bodies produce a ftiffnefs and rigidity 

 in the parts of thofc bodies into which they enter, t 

 It appears, by microfcopical obfervations upon falts, 

 that the figure of fome falts, before they Ihoot into 

 mafl^es, are thin, double wedged, like particles vdiich 

 have abundance of furface, in refpcft to their foli- 

 dity; and is the reafon why they fwim inw-ater, when 

 once raifed in it, though fpecifically heavier.- 



.3 



Thefe fmall points, getting into the pores of the 

 water, whereby they are alfo, in fome meafure, fuf- 

 pended in the winter time, when the heat of the fan 

 is not ordinarily ftrong enough to difiblve the falts 

 into a fluid, to break their points, and to keep them 

 in perpetual motion, being lels difturbed, are at more 

 liberty to approach one another ; and, by fliocting 

 into cryftals of the form above-mentioned, do, by 

 bot!i their extremities, infinuate themfelves into the 

 pores of the water, and by that means freeze it into a 

 folid form. And it is apparent, that the dimenfions 

 of water are increafed by freezing, the particles or 

 it being kept at fome dittance from one another, by 

 the intervention of the frigorific matter. .;;; ;-.\^ - ' 

 ■ But befides this, there aic many little volumes, or 

 fmall particles of air, included at feveral diftances, 

 both in the pores of the watery particles, and in the 

 interfl:ices formed by their fpherical figure. Now, by 



the infinuation of the cr)-fl;als, the volumes of air are 

 driven out of the wateiy particles, and many of '^^^^ 

 uniting, form larger volum.es, which thereby have a 

 greater force to expand them.felves than when they 

 are difperfed ; and fo both enlarge the dimenfions, 

 and leflen the fpecific gravity of v/ater thus congealed 

 into ice. 



And hence (fays Dr. Cheyne, from whom this laft ac- 

 count is taken^ we inay K^efs at the manner howwa- 



