438 



The object of the experiments related in this paper, is to trace 

 the source of the electricity which accompanies the issue of steam 

 of high pressure from the vessels in which it is contained. By 

 means of a suitable apparatus, which the author describes and de- 

 lineates, he found that electricity is never excited by the passage of 

 pure steam, and is manifested only when water is at the same time 

 present ; and hence he concludes that it is altogether the effect of 

 the friction of globules of water against the sides of the opening, 

 or against the substances opposed to its passage, as the water is 

 rapidly moved onwards by the current of steam. Accordingly it 

 was found to be increased in quantity by increasing the pressure and 

 impelling force of the steam. The immediate effect of this friction 

 was, in all cases, to render the steam or water positive, and the 

 solids, of whatever nature they might be, negative. In certain cir- 

 cumstances, however, as when a wire is placed in the current of 

 steam at some distance from the orifice whence it has issued, the 

 solid exhibits the positive electricity already acquired by the steam, 

 and of which it is then merely the recipient and the conductor. In 

 like manner, the results may be greatly modified by the shape, 

 the nature, and the temperature of the passages through which the 

 steam is forced. Heat, by preventing the condensation of the steam 

 into water, likewise prevents the evolution of electricity, which 

 again speedily appears by cooling the passages so as to restore the 

 water which is necessary for the production of that effect. The 

 phenomenon of the evolution of electricity in these circumstances 

 is dependent also on the quality of the fluid in motion, more espe- 

 cially in relation to its conducting power. Water will not excite 

 electricity unless it be pure ; the addition to it of any soluble salt 

 or acid, even in minute quantity, is sufiicient to destroy this pro- 

 perty. The addition of oil of turpentine, on the other hand, occa- 

 sions the development of electricity of an opposite kind to that 

 which is excited by water ; and this the author explains by the par- 

 ticles or minute globules of the water having each received a coat- 

 ing of oil in the form of a thin film, so that the friction takes place 

 only between that external film and the solids, along the surface of 

 which the globules are carried. A similar, but a more permanent 

 effect is produced by the presence of olive oil, which is not, like 

 oil of turpentine, subject to rapid dissipation. 



Similar results were obtained when a stream of compressed air 

 was substituted for steam in these experiments. When moisture 

 was present, the solid exhibited negative, and the stream of air po- 

 sitive electricity ; but when the air was perfectly dry, no electricity 

 of any kind was apparent. The author concludes with an account 

 of some experiments in which dry powders of various kinds were 

 placed in the current of air ; the results differed according to the 

 nature of the substances employed, and other circumstances. 



