158 PHILOSOPHICAL TRANSACTIONS. [ANN0 1781. 



I shall briefly relate some observations made on the cold produced by the evapo- 

 ration of other fluids besides asther. 



In a room, the temperature of which was 64° according to Fahrenheit's ther- 

 mometer, and in which the air was gently ventilated, I observed the effects pro- 

 duced by various fluids when thrown upon the ball of a thermometer. The ball 

 of this thermometer was quite detached from the ivory piece on which the scale 

 was engraved. The various fluids were thrown on the thermometer through the 

 capillary aperture of a small glass vessel, shaped like a funnel, and care was 

 taken to throw them so slowly upon the bulb of the thermometer, that a drop 

 might now and then fall from the under part of it ; except when those fluids 

 were used, which evaporate very slowly, in which case it was sufficient to keep 

 the ball of the thermometer only moist, without any drop falling from it. 

 During the experiment the thermometer was kept turning very gently round its 

 axis, in order that the fluid used might fall on every part of its bulb. This 

 method I find to answer much better than that of dipping the ball of the ther- 

 mometer into the fluid and removing it immediately after, or that of wetting the 

 thermometer with a feather. The evaporation, and consequently the cold pro- 

 duced by it, may be increased by ventilation, viz. by blowing with a pair of 

 bellows on the thermometer ; but this was not used in the following experiments, 

 because it is not easily performed by one person, and also because it occasions 

 very uncertain results. 



With the above described method I began to examine the effects of water, 

 and found, that the thermometer was brought down to 56°, viz, 8° below the 

 temperature of the room in which the experiment was made, and of the water 

 employed. This effect was produced in about 1 minutes time, after which a 

 longer continuation did not bring the mercury lower. By means of spirit of 

 wine the thermometer was brought down to 48°, which is only l6° below the 

 temperature of the room, and of the spirit employed. When the spirit of wine 

 is highly rectified, the cold produced by its evaporation is certainly greater than 

 when it is of the common sort ; but the difference is not so great as one, who 

 never tried the experiment, might expect. The. purer spirit produces the effect 

 much quicker. Using various other fluids, which were either compounds of 

 water and spirituous substances, or pure essences, I found that the* cold pro- 

 duced by their evaporation was generally in some intermediate degree between 

 the cold produced by the water and that produced by the spirit of wine. Spirit 

 of turpentine brought the thermometer only 3° lower than the temperature of 

 the room ; but olive oil and other oils, which evaporate either very slowly or not 

 at all, did not sensibly affect the thermometer. 



Wishing to observe how much electrization could increase the evaporation of 

 spirit of wine, and consequently the cold produced by it, I put the tube contain- 



