Hydro- electric Machine. 



201 



the convolutions of a multiplying wire which made sixteen 

 folds, and having its terrestrial magnetism partially neutralized 

 by a second needle in the usual way, was immediately deflected 

 by passing the current through the wire, and retained in a 

 state of oscillation between angles of about 20° and 30°. On 

 reversing the current the deflection took place in the opposite 

 direction, precisely as it would have done if voltaic electricity 

 had been used. 



A cylinder of soft iron, nine inches long and one inch in 

 diameter, wrapped with about eighty feet of copper wire, co- 

 vered with cotton and thickly varnished, had sufficient mag- 

 netism excited in it to influence very sensibly a compass needle 

 placed in its vicinity. 



Fig. 5 will illustrate the manner in 

 which this experiment was performed. 

 A is the bar of soft iron with the 

 copper wire coiled upon it, and B the 

 compass needle which turned upon a 

 point and was placed with one of its 

 poles at a distance of two inches from 

 the nearest extremity of the iron bar. 

 Upon passing the current of elec- 

 tricity through the wire, the needle 

 moved 5° towards the bar and re- 

 turned to its original place when the 

 current ceased. Again, when the di- 

 rection of the current was reversed, 

 the needle was repelled about 3|°, 

 making a total variation between the 

 two extremes of about 8|°. 



The time during which the ma- 

 chine remained in my hands after its 

 completion did not enable me to follow 

 up these various experiments to the extent I should have 

 wished, and I must therefore leave to others the task of pro- 

 secuting them further. 



Before I conclude this letter, I must beg to disclaim the 

 opinion which has been attributed to me in some notices of 

 your recent lecture upon Steam Electricity, viz. that the elec- 

 tricity arose from the passage of the water into the aeriform 

 state. I have long held that the emission of a certain pro- 

 portion of water in conjunction with the steam, was essential 

 to a high development of electricity ; and also that the effect 

 depended in a very great measure upon the nature and form 

 of the discharging orifice; and it has been by acting upon 

 these principles, for more than a year, that I have been enabled 



