420 On a new Mode of Artificial Congelation. 



But this very striking experiment is easily performed without a;iV 

 foreign aid. Having introduced mercury into the large bulb oi 

 a thermometer, and attached the tube to the rod of a transferrer, 

 let this be placed over the wide dish containing sulphuric acid, 

 in the midst of which is planted a very small tumbler nearly 

 filled with water. After the included air has been rarefied abor.t 

 fifty times, let the bulb be dipped repeatedly into the very cold 

 but unfrozen water, and again drawn up about an inch ; in this 

 way, it will become incrusted with successive coats of ice, to 

 the thickness perhaps of the twentieth part of an inch. The 

 water being now removed, the pendent icicle cut away from the 

 bulb, and its surface smoothed by the touch of a warm finger, 

 the transferrer is again replaced, the bulb let down within half 

 an inch of the acid, and the exhaustion pushed to the utmost. 

 When the siphon-gauge has come to stand under the tenth of 

 ail inch, the icy crust starts into divided fissures, and the me:- 

 tury, having gradually descended in the tube till it reach its 

 point of congelation, or 39 degrees below zero, sinks by a sud- 

 den contraction almost into the cavity of the bulb ; and the ap- 

 paratus being then removed and the ball broken, the metal ap - 

 pears a solid shining mass, that will bear the stroke of a hammer. 



Still greater Cold created. 



But a still greater degree of cold may be created, by applj-ing 

 tlie same process likewise to cool the atmosphere which encircles 

 the apparatus itself. A glass matrass was blown nearly of a 

 hemispherical shape, its bottom quite flat, and about three inches 

 in diameter^ and its neck about half an inch wide and cut square 

 over. The whole was covered with a coat of patent lint, which 

 takes up water very copiously, a portion of sulphuric acid was 

 next introduced, forming a layer of perhaps a quarter of an inch 

 thick, and a spirit of wine thermometer, having its bulb also 

 cased with wetted lint, was then inserted within the matrass, 

 a brass ring attached to the tube securing it in the right posi- 

 tion. Things being thus arranged, the matrass or flat bottle, 

 with its thermometer, was placed on a slender stool with glass 

 feet, about an inch above the sulphuric acid in the broad bason, 

 and the large receiver luted over it. The air was then partly 

 extracted, till the gauge came below one inch. In a iew minutes 

 the lint was frozen entirely, and looked white. After an interval 

 of a quarter of an hour, to allow time for the evaporation of that 

 icy coat to cool down the interior apparatus, the pump was again 

 urged, and the exhaustion pushed to about three-tenths of an 

 inch. In a short while, the inclosed thermometer sunk not 

 fewer than 180 degrees, and remained stationary, til! the ice had 

 wasted a^vay. 



