6l6 PHILOSOPHICAL TRANSACTIOfJS. [aNNO I7OI. 



being universal, and reaching no further than some few places in the liquor, it 

 may yet contribute to the great cold in the mixture of sal ammoniac and oil of 

 vitriol, in increasing the coagulum, so that the little particles which are vio- 

 lently agitated in this mixture, not being able to carry along with them in their 

 motion the coagulated parts, which are too gross, they drive them away from 

 their centre of motion : So that the almost half coagulated particles, being got 

 among these little whirl-pools, and pressed against each other, they stick close 

 together, coagulate more strongly, and lose their motion entirely ; which 

 causes a very great cold. And that the violent agitation in some parts of the 

 mixture contributes to its coldness, appears by the following experiment. 



I put some cold water into a large basin, and into the middle of it a glass 

 cucurbit full of water, equally cold ; and into the cucurbit I put a very good 

 thermometer, which I let lie a good while for a trial. When it was adjusted to 

 a degree proportionable to the cold of the water, I threw suddenly into the 

 water in the basin four or five shovels full of coals, well kindled ; and in an 

 instant the liquor of the thermometer descended 2 or 3 lines. After some 

 moments the liquor rose again, when the heat of the water in the basin was 

 communicated to the glass cucurbit. Now the cold of the water in the cu- 

 curbit cannot be attributed to any thing but the pressure or sudden condensa- 

 tion, which the fire caused in the water, in which it was put. Which conden- 

 sation may be explained in this manner : In the instant that the burning coals 

 were thrown into the water, the vortex of the subtile matter, by which it was 

 turned round, being pressed by the matter which environed it, scattered with 

 violence all the particles of the water ; which happening all at once in several 

 places of the water in the basin, all round the glass cucurbit, the particles which 

 environed the vessel being at once pressed on all sides, were condensed consi- 

 derably and successively. The vessel being in the centre of pressure, bore all 

 its weight, as well as that of the liquor, which contained it. And this liquor 

 lost by its condensation very much of the motion it had before, which was consi- 

 derable enough to cause the liquor of the thermometer to fall. This cold goes 

 off quickly, because all the water in the basin being very much heated, it 

 quickly heats also that in the glass cucurbit. 



The ordinary thermometers not marking the cold of the water so readily and 

 nicely as I wished, I had recourse to another sort of thermometer, which was 

 more exact. It consists of a bowl or bottle of glass, which has no opening, 

 but by a little tunnel at the end ; and which descends to the bottom. This 

 tunnel is open at both ends bc. b dips into the liquor e which is at the bottom 

 of the bowl. Fig. 1, pi. 16. The space of the bottle of glass is filled with 

 air, which has no communication with the exterior air. When the air contained 



