416 RECENT PROGRESS IN PHYSICS. 



To obtain a continuous evolution of the mixed gases from water sub- 

 jected to the action of heat alone, Grove constructed the apparatus 

 Fig. 56. shown in fig. 56 ; a and b 



are tubes of silver 4 inches 

 in length and 0.3 in diam- 

 eter, connected by two pla- 

 tinum caps to a tube of a 

 perforated platinum wire 

 0.125 inches diameter, the 

 bore having the diameter of 

 a large pin ; a is closed at 

 the extremity, and to the 

 extremity of b is fitted, by 

 means of a coiled strip of 

 bladder, the bent glass tube d. The whole apparatus is filled with 

 water freed from air, and, after having expelled the air from a by 

 heat, the end of the glass tube was immersed in a vessel of boiling 

 water. Heat is now applied by a spirit lamp, first to b and then to a, 

 until the whole boils ; after this the flame of an oxy-hydrogen blow- 

 pipe is directed upon the middle part of the platinum tube c, and when 

 this has obtained a high degree of ignition gas is evolved which, mixed 

 with vapor, soon fills the whole apparatus, and escapes through the 

 open end either into the open air or into a gas collector. 



The gas thus obtained left, after its detonation, a residue of 0.3 of 

 its volume, consisting of nitrogen and a trace of oxygen. 



That, in all these caries, the remnant consists of nitrogen is caused 

 by the great difficulty or even impossibility of absolutely removing all 

 the air from the water. 



This series of phenomena is very remarkable. While the detonating 

 gas, under the influence of heat, is condensed to vapor of water, we 

 have here exactly the opposite action, though to a very limited extent 

 only. The elaboration of the more intimate conditions and relations 

 of this decomposition of aqueous vapor, which might lead to an explan- 

 ation of the phenomenon, we must leave to the future. 



When Grove says " that these experiments afford some promise of 

 our being, at no distant period, able to produce mixed gases for pur- 

 poses of illumination, &c., by simply boiling water and passing it 

 through highly ignited platinum tubes, or by other methods," I cannot 

 help expressing my doubts whether, even if the manufacture on a 

 large scale should succeed, the detonating gas thus produced could 

 give more light and heat than the fuel consumed in its formation. 



§ 63. Application of galvanic ignition to blasting rocks. — It has for a 

 long time been known that gunpowder can be ignited by the electric 

 spark, as shown long ago by Franklin, and still repeated a^ one of the 

 usual experiments in the lecture room. But, although blasting by 

 means of frictional electricity is therefore possible, still there are too 

 many difficulties in the way of the process to allow us to expect its 

 introduction into practice. 



Hare was the first to employ the ignition of metallic wires by the 

 galvanic current in blasting. But his apparatus was too complex and 



