HEAT OR CALORIC. 97 



(c.) Such a flask, as that represented at No. 11, p. 100, is filled 

 with water, except an inch or two of the neck, which is occupied by 

 ether ; its mouth being covered by the thumb, it is inverted and se- 

 cured in the pneumatic cistern, and treated as in (6.) and with the 

 same result, only the return* of the water especially if the neck of 

 the flask is plunged deep, so that the water which comes in is very 

 cold, may be sudden ; it produces a violent whirl of the injected 

 water, which, if it does not break the flask, makes a very pleasing 

 experiment ; if, when the etherial vapor fills the vessel, the thumb 

 be used as a stopper, the ball of the flask may then be cooled, and 

 the water let in gradually, without endangering the vessel, but the 

 effect is much less striking. 



(d.) Ether boils instantly at the common temperature, in the Tor- 

 ricellian vacuum. Form this vacuum by using a strong tube, thirty- 

 three or thirty-four inches long, and a half or three quarters of an inch 

 in the bore, and then introduce a little ether through the mercury, in 

 which the tube stands, by depressing a small essence vial full 

 of that fluid, beneath the mouth of the tube, and turning it up ; as 

 soon as the ether arrives near the top of the tube, it flashes into 

 vapor, with violent ebullition and drives the mercury half or two 

 thirds down the tube ; if the tube be then inclined in a position as 

 nearly horizontal as possible, without removing its mouth from the 

 mercury, a great part of the ether will be recondensed, and the va- 

 por will be formed anew on raising the tube. 



The above experiment is very strikingly exhibited by filling the tube 

 with mercury, except an inch at the top, which is filled with ether, 

 and then the orifice being closed with the thumb or the hand, it is 

 introduced, in an inverted position, into the mercurial cistern, when 

 as soon as the hand is withdrawn, the tube, at that moment occupied 

 by the mercury and ether, becomes instantly, in a great measure 

 filled with etherial vapor, which, as before, drives the mercury down. 



6. A glass tube, six or eight feet long, and one inch wide, closed at 

 one end, and the other fitted with a stop-cock, being screwed to the 

 plate of the air pump, may be exhausted to the greatest degree that 

 the pump is capable of; if the pump is a good one, the atmosphere, 

 when the tube is unscrewed and opened beneath water, will force 

 it up in a jet and nearly fill it : a colored fluid gives the most beauti- 

 ful experiment. 



7. If the exhausted tube be opened under mercury, a jet of that 

 fluid will be thrown in, and the column that is formed may be thirty 

 inches high. On lifting the tube out of the mercurial cistern, the 

 atmosphere will enter, and, because there is still a good vacuum 

 above the mercury, the latter fluid will be pushed up nearly or quite, 

 to the top of the tube, and will then fall, and the same effect will 



13 



