156 ANNUAL OF SCIENTIFIC DISCOVERY. 



about the end of winter or beginning of spring. He describes mists 

 which he considers to' have been thus formed in the lake district of 

 Cumberland. To a similar cause, also, he refers the phenomenon 

 termed sweating, which is the precipitation of moisture on walls and 

 flagged floors excluded from the influence of fire. He also attributes 

 to a warm south wind, succeeding a very cold north wind, the depo- 

 sition of a large quantity of moisture which he once saw on the pic- 

 tures in the gallery of a nobleman in Devonshire, and quotes the 

 saying of Honier, 



" The south wind Avraps the mountain-top in mist." 



The Freezing of Water and Formation of Hail. This subject 

 has been investigated by Prof. Dafour, of Lausanne, who has pub- 

 lished the following conclusions as the result of his researches : 



1st. When water is kept in suspension in a fluid medium, free from 

 all contact, it seldom freezes at 32 Fah. The liquid state is pre- 

 served at 23 and 14 above zero, and even at 13 below zero, Fah. 

 2d. Solidification is produced under divers influences (contact of 

 solids, etc.). 3d. Under suitable circumstances freezing may be pro- 

 voked at a temperature lower than 32, and solid spheres obtained 

 analogous to hail. 4th. Hail is probably produced when the watery 

 globules suspended in an agitated atmosphere are cooled down lower 

 than 32, the condensation and congelation of vapor on their surface 

 contributing to increase their size. 5th. The principal characteristics 

 of hailstones may be suitably explained in supposing their origin to 

 have been that which has been indicated above. 



THE FREEZING AND BOILING POINTS OF WATER. 



M. L. Dufour has communicated to the French Academy the 

 results of some interesting experiments showing that water and cer- 

 tain other substances may be maintained in the liquid condition at 

 temperatures much beyond the point at which they usually pass into 

 either the solid or vaporous state, by placing them in a fluid menstruum 

 of the same density as themselves, and with which they are not rnisci- 

 ble. Globules of water thus suspended in perfect equilibrium retain 

 the fluid condition through a much longer range of temperature than 

 is possible under other circumstances. 



The boiling point of liquids is known to vary considerably, and to 

 be particularly affected by the nature of the vessel in which the liquid 

 is contained. With water the boiling point is higher in a glass than 

 in a metallic vessel. When the surface of the glass has been specially 

 cleansed with oil of vitriol the discrepancy becomes still more marked. 

 When placed under the conditions of a water hammer, in which it is 

 entirely free from air, and contained in a glass tube, Donne has 

 shown that it may, by careful heating, be raised to 135 Cent, with- 

 out passing into the vaporous condition. The deviation in such cases 

 is attributed to the force of adhesion existing between the liquid and 

 the surface of the vessel, and the absence of air from solution. 



In M. Dufour's experiments, however, the result cannot be attributed 

 to the absence of air, or to the adhesion of the liquid to a solid ; on 



