Page:Popular Science Monthly Volume 13.djvu/712

692 a conductor, rubbing against iron, another conductor, will accumulate electricity. But this is opposed to our experience. It requires friction with a non-conductor to excite electricity. We have instances daily of the passage of water through pipes, sometimes with great force and velocity. Did friction between the two excite electricity, it should be produced in great quantities. But no such effect has been observed.

Mr. Patterson, who experimented with the same boiler that Armstrong used, tried the effect of blowing out water instead of steam through a pipe from the boiler, and no electricity was thereby produced (Philosophical Magazine, vol. xvii., p. 459, 1840).

Were it indeed true, as Faraday assumed, that the friction of water against the sides of the exit-pipe produced electricity, it would be conducted away as fast as formed by the metallic tube to the negative boiler. Indeed, when he placed in the tube any saline or acid substance that increased the conducting power of water, no electrical effects were obtained. In some cases negative electricity, like that of the boiler, was manifested.

I do not find, from an examination of Faraday's paper, that he made any experiment upon steam at a distance from its exit, where its condensation to water mostly took place. His mode of experimenting he describes as follows. He says (section 2082):

"When the issuing steam produces electricity, there are two ways of examining the effect. Either the insulated boiler may be observed or the steam examined; but these states are always contrary one to the other. . . . To examine the state of the boiler or substance against which the steam is excited, is far more convenient, as Mr. Armstrong has observed, than to go for the electricity to the steam itself. And in this paper I shall give the state of the former, unless it be otherwise expressed."

I infer, therefore, that, in all the experiments hereinbefore detailed, the tests for electricity were made at or near the boiler, and the very important inquiry of the electrical effects at a distance, where condensation alone was concerned, seems not to have attracted his attention. This point, however, has been fully investigated by others.

Mr. Patterson attached ten or twelve pointed wires to a copper rod. These were bent downward and held in the escaping steam. He says (ibid., page 458):

"The sparks were larger when the points of the conductor were held in the steam about two feet above the valve; but large sparks were obtained by holding the conductor entirely out of the cloud of steam and at a distance from it, for the air in the wooden shed in which we operated became speedily electrical throughout. The electricity was positive."

Mr. Armstrong also states (ibid., page 453):

"Upon trying the steam in the first instance by the method adopted in the previous cases, that is to say, by standing upon an insulated stool and holding with one hand a light iron rod immediately above the safety-valve while the