VOL. XXII.] PHILOSOPHICAL TRANSACTIONS. 6l5 



enough for that, they there lose that little activity which they had, and coagu- 

 late, if not all, at least the greatest part : and this want of action is the 

 cause of that great cold which we perceive there. 



Hitherto, I have only considered simple cold solutions of salts, in which 

 there is no augment^ition of a sensible motion ; let us now pass to the solutions 

 of the second class, which are the cold fermentations, in which the cold appears 

 as a consequence of the agitation of the parts of the liquor. In order to show 

 the reason of cold fermentations, I own that heat and cold in liquors are nei- 

 ther more nor less than motion in the little parts of these liquors, caused by the 

 continual current of the subtile matter in their intermediate spaces. And I 

 affirm, that every time this motion is diminished, and when the course of the 

 subtile matter is interrupted, the liquor appears less hot, or more cold. This 

 being supposed, if we attend to what happens in cold fermentations, we shall 

 observe on the one hand, for the most part, very considerable coagulations, 

 and a very sensible thickening of the liquors ; on the other hand, we shall per- 

 ceive a very violent agitation of some of the parts of these mixtures: Many 

 vapours are exhaled, the matter swells, emits many bubbles, and ferments with 

 noise. And thus I conceive all these effects are produced. 



In the mixture which I made of salts with acid liquors, the greatest part of 

 the liquor coagulating with a part of the salts, its motion was much abated in a 

 little time ; but its parts not being able to coagulate, without stopping or weak- 

 ening the current of the subtile matter, this matter finding the passages shut 

 up, takes its course by the interstices, which remained between the coagulated 

 particles, where the passage was yet free ; and as it glided away in a quantity 

 together, it caused a very considerable agitation in the parts it met with in its 

 passage ; which agitation produces the fermentation we perceive, raises bubbles 

 of air and smoke, and swells the matter with so much the more violence, that all 

 the parts of the liquor, being almost half coagulated, hinder the motion and 

 agitation of these little particles. Nevertheless this agitation, how violent 

 soever it may appear, is not considerable enough to break the coagulum en- 

 tirely, which is formed in the liquor, nor consequently to overcome the cold, 

 which causes this coagulation. All it can do, is to preserve still some kind of 

 fluidity. In short, the more these mixtures are disposed to coagulate, the 

 more they excite the cold. This we may see in the mixture of sal ammoniac 

 with oil of vitriol, in which the coagulum becomes so strong, that at last, it 

 forms above the liquor a very thick saline crust. In the mixture of other salts 

 with weaker acids, as in the mixture of volatile salts with spirit of vinegar, the 

 coagulum can hardly be perceived ; nor is the cold so considerable as in the former. 



I add further, that even the violent agitation which this mixture causes, not 



