VOL. LXXI.] PHILOSOPHICAL TRANSACTIONS. 159 



ing the spirit into an insulating handle, and connected it with the conductor of 

 an electrical machine, which was kept in action while the experiment was per- 

 formed ; by these means the thermometer was brought down to 47°. Having 

 tried the 3 mineral acids, I found that instead of cooling they heated the ther- 

 mometer, which effect I expected ; since it is well known, that those acids at- 

 tract the water from the atmosphere, and that heat is produced by the combina- 

 tion of water and any of them. The vitriolic acid, which was very strong and 

 transparent, raised the thermometer to 102°; the smoking nitrous acid raised it 

 to 72°; and the marine acid raised it to 66°; the temperature of the room, as 

 well as of the acids, being 64°, as mentioned above. 



The apparatus which I contrived for the purpose of using the least possible 

 quantity of aether in freezing water, &c. consists in a glass tube, terminating in 

 a capillary aperture, which tube is to be fixed on the bottle that contains the 

 aether. Fig. 11, pi. 3, exhibits such a tube, round the lower part of which, at 

 a, some thread is wound, to make it fit the neck of the bottle. When the ex- 

 periment is to be made, the stopper of the bottle containing the aether is re- 

 moved, and the above-mentioned tube is fixed on it. The thread round this 

 tube should be moistened a little with water or spittle before it is fixed on the 

 bottle, to prevent more effectually any escape of aether between the neck of the 

 bottle and the tube. Then holding the bottle by its bottom fg, fig. 12, and 

 keeping it inclined as in the figure, the small stream of aether issuing out of the 

 aperture d of the tube de, is directed on the ball of the thermometer, or on a 

 tube containing water or other liquor required to be congealed. 



^Ether being very volatile, and having the remarkable property of increasing 

 the bulk of air, does not require any aperture, through which the air might 

 enter the bottle, in proportion as the aether goes out : the heat of the hand is 

 more than sufficient to force the aether in a stream from the aperture d. After 

 this manner, throwing the stream of aether on the ball of a thermometer in such 

 quantity as that a drop of aether might now and then, for instance every 10 

 seconds, fall from the under part of the thermometer, I have brought the mer- 

 cury down to 3°, viz. 2Q° below the freezing point, when the atmosphere was 

 somewhat hotter than temperate, and that without blowing on the thermome- 

 ter. When the aether is very good, viz. is capable of dissolving elastic gum, 

 and the thermometer has a small bulb, not above 20 drops of aether are required 

 to produce this effect, and about 2 minutes of time ; but when the aether is of 

 the common sort, a greater quantity of it, and a longer time, are necessary to be 

 employed, though at last the thermometer is brought down very nearly as low 

 by this as by the best sort of aether. 



To freeze water by the evaporation of aether, I take a thin glass tube about 4 

 inches long, and about -i- of an inch in diameter, hermetically closed at one end,, 



