228 Misccl/tiiu'oiis InteUigcmc. 



massbeint^ put into the retort instead of coal will produce more 

 gas, and be less offensive than the same quantity of canal coal. 

 This process will probably be found very convenient in some 

 circumstances for the consumption of the tar produced by the 

 distillation of coal in gas-works. 



10. On the formation of Ice in the beds of Rivers. — Dr. 

 RI'Keevcr of Dublin, whilst reasoning on this particular forma- 

 tion of ice, which has never yet been well explained, suggests, 

 that it may be occasioned by radiation just in the way that hoar- 

 frost is formed. It is mentioned from the observations of 

 Mr. Garnet, in a former volume of this Journal, that such ice 

 is seldom seen adhering to any substance except rock, stones, 

 or gravel ; that it is always found in greatest abundance in 

 proportion to the magnitude and number of the stones com- 

 posing the bed of the river, combined with the velocity of 

 the current; and that it does not occur where mud or clay 

 is deposited. Dr. M'Keever thinks it probable, that in conse- 

 quence of the greater radiating powers, as regards heat, of these 

 substances on which the ice is deposited, an effect of depression 

 of temperature may be produced by the heat they throw off 

 into space, sufficient, when it takes place in water nearly at the 

 freezing point, to decide the formation of ice at their surface, 

 and the rapidity of the current of cold water, he thinks, may be 

 active in reducing the temperature of the bed of the river more 

 rapidly, as well as in removing the heat evolved by the con- 

 gelation of the successive portions of water. The great objection 

 to this theory, it is remarked, is Professor Leslie's statement, 

 that no radiation takes place in water ; but it is justly observed, 

 that from the evident difficulty of making the experiment ac- 

 curately, that point is not yet decided. — Ann. Phil. iii. 187. 



1 1 . Singular Congelation of Water. — M. Pictet relates, that 

 whilst engaged in examining some subterranean excavations in a 

 bed of lava, near Niedermendig, he had occasion to observe a 

 fact that had previously drawn his attention in many natural 

 caverns in the midst of summer, and of which he had not yet 

 found an explanation. " 1 observed in some places water 

 falling drop by drop from the roof on to the floor, or against 

 the sides of the cavern. Wherever this happened, there was 

 beneath, a mass of ice of a certain thickness ; nevertheless the 

 temperature of the air was 3.5 R (39.8° F.), and 1 believe that 

 at no time did it ever descend to zero in these subterraneous 

 places. — Geneva Memoires i. p. 151. 



12. On the heat of solutions crystallized by exposure to air. — 

 When a hot saturated solution of Glauber's salt is suffered to 

 cool in a closed flask or phial, it remains fluid until the stopper 



