162 CORRELATION OF PHYSICAL FORCES. 



in books of authority that there is no instance of two or more 

 solids or liquids, or a solid and a liquid, combining and pro- 

 ducing a compound which is entirely gaseous at ordinary 

 temperatures and pressures. The substance gun-cotton, how- 

 ever, discovered by Dr. Schoenbein, very nearly realises this 

 proposition. 



Dr. Andrews has arrived at the conclusion, after careful 

 experiment, that in chemical combinations where acids and 

 alkalies or analogous substances are employed, the amount of 

 heat produced is determined by the basic ingredient, and his 

 experiments have received general assent ; although it should 

 be stated that M. Hess arrived at contrary results, the acid 

 constituent according to his experiments furnishing the meas- 

 ure of the heat developed. 



Light is directly produced by chemical action, as in the flash 

 of gunpowder, the burning of phosphorus in oxygen gas, and ali 

 rapid combustions : indeed, wherever intense heat is developed, 

 light accompanies it. In many cases of slow combustion, 

 such as the phenomena of phosphorescence, the light is apparent- 

 ly much more intense than the heat ; the former being obvious, 

 the latter so difficult of detection that for a long time it was 

 a question whether any heat was eliminated ; and I am not 

 aware that at the present day, any thermic effects from cer- 

 tain modes of phosphorescence, such as those of phospho- 

 rescent wood, putrescent fish, &c., have been detected. 



Chemical action produces magnetism whenever it is thrown 

 into a definite direction, as in the phenomenon of electrolysis. 

 I may adduce the gas voltaic battery, as presenting a simple 

 instance of the direct production of magnetism by chemical 

 synthesis. Oxygen and hydrogen in that combination chemi- 

 cally unite ; but instead of combining by intimate molecular 

 admixture, as in the ordinary cases, they act upon water, i. e. 

 combined oxygen and hydrogen, placed between them so as 

 to produce a line of chemical action ; and a magnet adjacent 

 to this line of action is deflected, and places itself at right 



