278 Literary and Philosophical Society. 



electro-magnetic apparatus. The great merit of this appa- 

 ratus consisted in the improved adaptation of the magnets, 

 batteries, &c., to one another, by means of which Mr. Stur- 

 geon was enabled to perform, with a voltaic battery of the 

 size of a pint pot, experiments which had previously required 

 the use of a cumbrous and costly battery. The Society of 

 Arts testified their sense of the importance of this con- 

 tribution by awarding to its author their large silver medal, 

 with a purse of thirty guineas.' . . . 



'About this time Mr. Sturgeon made his great discovery 

 of the soft iron electro-magnet, and having observed the 

 high degree of polarity acquired by a straight bar of iron 

 on making a current of electricity to circulate around it, 

 as well as the suddenness with which the direction of 

 polarity could be reversed by changing the direction of 

 the current, he proceeded to construct electro-magnets on 

 the same principle, but bent into the form of a horse-shoe, 

 so that the poles, by being brought near one another, 

 could concentrate their action on any given object. This 

 soft iron electro-magnet has entered into the structure of every 

 form of electric telegraph. 



' Passing over several highly valuable communications 

 to the " Philosophical Magazine," which, even at this day, 

 would amply repay a careful study, we find him, in 1830, 

 publishing a pamphlet, entitled " Experimental Researches 

 in Electro-Magnetism, Galvanism, &c,," comprising an ex- 

 tensive series of original experiments. In this work Mr. 

 Sturgeon first pointed out the superior effects to be derived 

 from the use of amalgamated plates of rolled zinc in the 

 voltaic battery, instead of the unprepared cast zinc, then 

 in general use. He prepared his plates by dipping them 

 first into a dilute solution of acid, to cleanse their surfaces. 



