156 ANNUAL OP SCIENTIFIC DISCOVERY. 



while out of thirty-three liquids there was an increase in twelve, 

 and a decrease in twenty-one cases. In fourteen cases the specific 

 heat increased during the passage of the substance from the gas- 

 eous to the liquid state, and it was reduced in eleven cases while 

 changing from liquid to solid. From this it was probable that the 

 increase in the specific heat of a compound solid body above that 

 of its elements did not depend simply on its being .solid, but, on 

 the contrary, that it was solid because its specific heat exceeded 

 that of its elements. The following considerations would perhaps 

 throw some light on the subject : When any substance is heated, 

 part of the heat is expended in producing expansion, and the other 

 part in raising the temperature, and the sum of these two is equal 

 to the specific heat. If a gas, confined under a constant pressure, 

 is heated, it will be found to have a greater specific heat than if its 

 volume be constant, the reason being that in the former case some of 

 the heat is absorbed in producing expansion ; for the heat cannot do 

 two things at the same time, and that which produces the expansion 

 cannot affect the thermometer. When heat is applied to a mass of 

 ice, the temperature rises to thirty-two degrees, and then becomes 

 stationary ; this is the result of the difference in resistance that the 

 heat experiences at the two outlets, the greatest amount passing to 

 that at which there is least resistance. Hence the molecular force 

 of a solid body must dimmish as the temperature rises ; at thirty-two 

 degrees the molecular force of ice cannot overcome the repulsive 

 force. On heating a gas, there is no loss from molecular influences, 

 but with a solid, part of the heat is taken up in producing molecu- 

 lar changes, and, therefore, the less heat a solid contains, the more 

 does it resemble a gas in this respect, the specific heat increasing 

 with the rise of temperature ; from which it follows that the higher 

 the melting point of a solid the less is the specific heat, which is ex- 

 perimentally found to be the case. In those cases of combination in 

 which a change in one of the elements from a solid to a fluid state, or 

 the contrary, took place, a change in the specific heat of the result- 

 ing compound could be accounted for. On the whole, it would 

 appear that the changes in the specific heat of bodies that occurred 

 during combination were due not only to chemical action, but also 

 to molecular changes; the real specific heat of an atom remaining 

 probably the same under all conditions. 



IMPROVEMENT IN THE OXYHYDROGEN LIGHT. 



At a recent meeting of the Manchester Philosophical Society, Mr. 

 Alfred Fryer stated that he had recently been making a series of 

 experiments with the oxyhydrogen light, with a view to determine 

 what substance made incandescent produced the greatest amount 

 of light. He operated on various salts of calcium, magnesium, stron- 

 tium, barium, and also upon some other substances. The best results 

 were obtained from magnesium. The sulphate of magnesia, when 

 baked, yielded a bright light, but was decomposed by the heat ; and 

 the sulphurous acid escaping was very unpleasant. Calcined mag- 

 nesia succeeded the best of all ; but when the powder was used, the 

 gases blew it away. When the powder was mixed with water, and 



