168 Intelligence and Miscellaneous Articles. 



was kept from the side of the vessel, and floated in a medium of the 

 same density as its own. The medium to be employed ought to 

 exceed 100° without boiling, have the same density as water, and 

 not form aqueous mixtures. Oils are unsuitable, but certain essences 

 realize these conditions. 



Essence of cloves, to which a small quantity of oil has been added, 

 forms a liquid in which water remains in equilibrium in round 

 spheres, and perfectly moveable in the interior. If heated carefully, 

 a temperature far above 100° may frequently be attained before the 

 ebullition of the water ensues. A temperature of 120° and 130° is 

 frequently reached ; and I have often had these aqueous spheres 10 

 millims. in diameter at 140° to 150°. Smaller spheres, 1 to 2 mil- 

 lims. in diameter, have often been raised to 170°, and even 175°; 

 that is, to temperatures at which the tension of aqueous vapour is 

 8 atmospheres. The water had undergone no preparation ; it was 

 neither distilled nor free from air. At these high temperatures there 

 is not, as might be thought, a slow and continuous ebullition. The 

 spheres are as limpid and calm at 150° as at 10°. 



Ebullition ensues when the globules come in contact with a solid. 

 If, carried by the currents which are produced during the heating, 

 they strike against the side of the vessel or the bulb of the thermo- 

 meter, there is a sudden production of vapour. The globule, which 

 has become somewhat smaller, is driven to some distance from the 

 point at which the explosion is produced, but it continues to float. 

 If, when the temperature exceeds 115° to 120°, the aqueous globule 

 is touched with a glass or metal rod, a similar effect is produced ; an 

 explosion takes place at the point of contact, a bubble of vapour is 

 disengaged which traverses the essence, and the globule is driven 

 away as if the point had exerted on it a sudden repulsion. The solids 

 best fitted for producing this effect are a pointed piece of wood or of 

 charcoal. Glass or metal rods occasionally fail ; the contact of 

 saline crystals is generally successful. 



The preceding phenomena may also be produced with other liquids 

 when heated under suitable conditions. Chloroform, for example, 

 heated in a solution of chloride of zinc, may be raised to 90° or 100°. 



It is natural to connect these phenomena with those in which the 

 contact of a solid induces the crystallization of supersaturated saline 

 solutions, as well as with the sudden solidification of water, sulphur, 

 &c, reduced below the ordinary temperature of solidification. They 

 are also intimately connected with the phenomenon of liquids re- 

 sisting solidification when they are immersed in a fluid medium. It 

 appears as if the contact of solids were a determining cause for the 

 change of condition in liquids ; and it may be that the limits of tem- 

 perature which we have assigned to the different conditions of bodies 

 are less absolute than they appear. — Comptes Rendus, May 13, 1861. 



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