30 REPORT — 1856. 



It therefore occurred to Mr. Whitehouse that the amount of magnetic force deve- 

 loped by the current in its passage through fine wire surrounding an electro-magnet, 

 seemed 'to offer the most ready, and at the same time the most practical mode of 

 attaining tlie object ; — an idea which received confirmation from the fact, that when- 

 ever such currents were used in telegraphy, they were always received upon and made 

 to actuate electro-magnets. 



He therefore wound an electro-magnet with fine wire, placing its poles very near 

 to a keeper of soft iron, poised in the manner of a lever steelyard and loaded to any 

 given weight ; the current either lifted or did not lift the given weight, and this was 

 the test of what Mr. W. proposed to call its " value " in telegraphy. 



So delicate was this test that he had been able to determine accurately the " value," 

 as it may be termed, of a current too feeble in its energy, and too brief in its dura- 

 tion, to give the slightest indication of its presence on one of the most sensitive 

 "detectors" usually employed in critical telegraphic operations. 



He had actually weighed with accuracy a current whose force was represented by 

 '-ths of a grain ; and on the other hand currents with a wide range of quantity and 

 intensity, and of varying amounts of force up to no less than 600,000 grains. 



Mr. Whitehouse then described in detail the principle and construction of the 

 instrument. The reels of fine wire were so arranged as to be easily removeable, in 

 order to substitute others carrying wire of different gauges, or even without this 

 change any two reels might be either joined up in series for intensity or in parallel 

 currents, which thereby halved the length while it doubled the area of conducting wire. 



Mr. Whitehouse then illustrated its uses and practical capabilities. 



1st. It had contributed valuable aid in the analysis of several forms of induction 

 coils, varying in size and construction ; it not only estimated in grains the value of 

 each' secondary current thus produced, but approximatively determined their relative 

 amounts of quantity and intensity, by noting the arrangement of wire which gave 

 the best result. . .... , 



2ndly. It speedily indicated the advantage of using mduction coils in pairs rather 

 than singly, under which head some surprising results were given, the near presence 

 of an unexcitcd iron bar augmenting the value of the current in the coil under 



observation. . ,, , . . ■ . i- 



3rdly. It would evidently afford the means of practically determining a point of 

 considerable interest in the comparison of voltaic and magneto-electric currents, 

 to the solution of which Mr. Whitehouse had pledged himself: this was to ascer- 

 tain the economico-practical limits of battery series ; because the penetrating 

 power or intensity and value of currents so produced might hereby be accurately 

 compared with the force of coil currents educed from batteries of much simpler and 

 less wasteful construction, consisting only of one or two elements, instead of 

 hundreds. . 



4thly. It had, conjointly with the use of a pendulum and automatic recording 

 arrangements, led to the production of a series of curve diagrams, representing a 

 minute analysis of any given current, denoting its force, however variable, in the 

 several fractions of a second of time. 



5thly. It had enabled Mr. Whitehouse, with the assistance and cooperation of 

 Mr. Bright of the Magnetic Company, after weighing the value, upon short circuit, 

 of the currents from many of their magneto-instruments, so as to determine their 

 average value, to weigh the same currents after working through various distances, 

 from 40 to 320 miles of subterranean and submarine wires ; thus showing with 

 certainty and minute accuracy the loss due to the combined influence of resistance, 

 induction and defective insulation. 



Lastly. It had done good service in working out the laws relating to induction in 

 submarine circuits ; and some striking illustrations were given in conclusion. 



Working upon a 498 mile length of very perfectly insulated cable-wire, the phe- 

 nomena of induction and retardation, of charge and discharge, as originally described 

 by Faraday, were exhibited in a remarkable manner. 



A current, lifting 18,000 grains on short circuit, was sent into the long wire, the 

 further end of which was insulated ; but on cutting off the battery, and instantly 

 discharging the wire to earth through the same instrument, it gave a lifting power 

 of 60,000 grains j so strikingly cumulative was the tendency of this gigantic Leyden 



