60 MR. J. P. JOULE ON THE LIFE AND WRITINGS 



sisted in the improved adaptation of the batteries, magnets, 

 &c. to one another, by means of which he was enabled to 

 perform with a galvanic arrangement, no larger than a pint 

 pot, experiments which had previously required the use of a 

 cumbrous and costly battery. A principal improvement was 

 effected by increasing the size and power of the magnet, Mr. 

 Sturgeon having had the sagacity to observe that the intensity 

 of the action was more advantageously augmented by an 

 increase of the magnetic force, than by an enlargement of the 

 size of the conductors of electricity, whereby the friction on 

 the pivots of the revolving apparatus would have been made 

 too sensible. The Society of Arts testified its sense of the 

 importance of this contribution, by awarding to its author its 

 large silver medal, with a purse of thirty guineas. 



The most important piece of apparatus in the above collec- 

 tion was a bent bar of iron, surrounded with a coil of conducting 

 wire. It was the earliest contrivance for showing the extra- 

 ordinary and instantaneous inductive effect of a voltaic current 

 on soft iron. I have already adverted to the magnetization 

 of steel needles by Arago and Davy, but it appears that Mr. 

 Sturgeon was the first who observed the wonderful facility 

 with which soft iron can be made intensely magnetic by the 

 galvanic current, as well as the extreme rapidity of the action. 

 Mr. Sturgeon appears to have discovered the soft iron electro- 

 magnet, and to have constructed it both in the straight and 

 horse-shoe shape as early as 1823. The soft iron electro- 

 magnet has been since introduced into most electric tele. 

 graphs. 



A paper published in the Philosophical Magazine for 

 June, 1826, contains a discussion of the cause of difficulty of 

 firing gunpowder by electrical discharges. Mr. Sturgeon 

 showed that in order to succeed, it was necessary to place a 

 body of low conductive power in the circuit, such as a piece of 

 wet thread. The violence of the discharge was by this means 

 so much diminished, that the electric fluid from eight feet of 



