VOL. XXXIII.] fHlLOSOPHICAL TRANSACTIONS. 23 



M. Fahrenheit's method of exhausting was thus; a glass ball, furnished with 

 a small tube.. 3 or 4 inches long, and tapering at the extremity, is heated over 

 a fire; after which the extremity of the tube is immersed in water, till by the 

 cooling of the air, contained in the ball, it become filled with some drops of 

 the water; and then it is held with a pair of tongs over the broader flame of a 

 lamp, or over live coals, till the water in the ball begin to boil, and the vapour 

 forcibly burst out; this boiling is continued for some time, after which the ball 

 is removed from the fire, and the flame of a candle applied to its extremity. 

 As the ball cools, the vapour rarefied by the fire, is successively condensed, and 

 its egress gradually diminished; and as soon as it entirely ceases, the extremity 

 of the tube melts, and the ball is hermetically sealed and exhausted. Whether 

 all the contained air be well exhausted in this manner, may be tried by breaking 

 the extremity of the tube under mercury; for then the ball will be entirely filled 

 with mercury, if it be carefully broken without admitting the external air. 

 You may also break it under water; but though it be done ever so carefully, 

 the ball will not be completely filled with water; for, while the water enters 

 the exhausted ball, the air, which is always mixed with water, separates from it 

 into very small bubbles, which after uniting, form a larger one in the ball. In 

 the same manner the ball maybe exhausted, if the third, the half, or a greater 

 part of the ball be required to be filled with water; for, it is first filled with the 

 desired quantity of water, and then, after boiling the water, it is hermetically 

 sealed. 



The experiments were as follow: March 2, 1721, he exposed to the cold a 

 glass ball, about an inch in diameter, exhausted in the manner abovementioned; 

 and filled with rain-water almost half full; the temperature of the air in the 

 thermometer was marked at 15 degrees. In an hour after, he found the water 

 still fluid in the ball. He then left the ball exposed all night in the open air, 

 and next day, viz. the 3d of March, at 5 o'clock in the morning, he found the 

 water still fluid, and the thermometer at the same degree; the cause of which 

 unexpected phenomenon he attributed to the absence of the air. To discover 

 the truth of this conjecture, he broke the extremity of the tube; that the 

 exhausted ball might be again filled with air; on which the whole mass of water 

 was suddenly mixed with very thin lamellae of ice. He broke the ball, and 

 putting some of the ice into some water in a glass cup, he observed it floated. 



A little time after, he observed all the water mixed with icy lamelias; yet the 

 greatest part of the water still continued fluid between the interstices; the ther- 

 mometer, put into this mixture, stood at 32 degrees. On repeating the expe- 

 riment with two other balls, and after preparing them iu the manner above- 

 mentioned, he exposed them for an hour in the open air, the thermometer 



