NATURAL PHILOSOPHY. 157 



the contrary, contact with a solid produces an instant gush of vapor. 

 His first experiment is as follows : Some linseed oil is heated in a 

 dish to 105 Cent, or 110 Cent., and a few drops of water dropped 

 in, which sink to the bottom of the vessel. The moment they touch, 

 a sudden formation of vapor takes place, and the globule, a little less- 

 ened, is repelled a short distance from the bottom. It again sinks till 

 it touches, when it again boils, and is again repelled. AVhile the 

 globule is floating through the oil no evaporation takes place ; it is 

 only on coming into contact with the solid that vapor is formed. 



M. Dufour's next experiment consists in using a medium having 

 the same density as water, and in which, consequently, the globules 

 remain in equilibrium, permanently floating in the centre ; the 

 medium being capable of bearing a temperature above 100, and not 

 being miscible with water. Essence of cloves, to which a small quan- 

 tity of oil has been added, constitutes a fluid answering to these condi- 

 tions. Water remains floating in round spheres with perfect freedom 

 of motion in the centre of this mixture. Under these circumstances, 

 if heat be carefully applied, a temperature far above 100 Cent, may 

 be obtained without the ebullition of the water ensuing. 120 or 130 

 Cent, is frequently reached, and spheres of water ten millimetres in 

 diameter have been thus raised to 140 and 150 without changing. 

 Smaller spheres, one to two millims. in diameter, have been raised to 

 170 and even 175 Cent.: that is to say, a temperature at which 

 steam has a tension equal to eight atmospheres (or one hundred and 

 twelve pounds). The water used had not been prepared; it was 

 neither distilled nor freed from air. At these high temperatures the 

 globules were as calm and transparent as at 10. When the globules 

 came into contact with a solid, then ebullition instantly ensued. If 

 carried against the side of the vessel or against the bulb of the ther- 

 mometer, a sudden formation of vapor was the result, and the globule 

 was repelled some distance from the point. By touching the globule 

 when at 115 or 120 with a glass or metal rod, or, better, a point of 

 wool or charcoal, a similar effect was produced ; an explosive forma- 

 tion of steam taking place, and the globule being driven away as if 

 the point had exerted some repulsive force. 



These phenomena may also be produced with other liquids treated 

 under the same conditions. Chloroform may be -so heated when 

 floating in a solution of cloride of zinc to a temperature of 90 or 100 

 Cent. 



By means similar to the above, M. Dufour has equally succeeded in 

 retarding the freezing of water. A mixture of chloroform and oil of 

 sweet almonds is made, in which globules of water float in equilibrium. 

 By cooling the mixture, the water scarcely ever freezes at Cent. 

 Its temperature sinks to 6, 10 before congelation occurs, and 

 globules have even been reduced to 20 Cent, without solidi- 

 fying. Ultimately the globules either pass into solid grains of ice, or 

 simply freeze on the surface, depending on the size and amount of 

 reduction in temperature. The persistence with which the water 

 retains the liquid state, is, however, remarkable. The mixture con- 

 taining the globules may be shaken, and foreign bodies introduced, 

 without solidification resulting. By touching the sphere, however, 

 with a lump of ice, congelation is immediately effected. When one 



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