80 SCIENCE IN SHORt CHAPTERS. 



hitherto constructed were defective in one f undamental ele- 

 ment of their arrangement. The thick copper wire sur- 

 rounding the soft iron core necessarily follows a spiral 

 course, like that of a coarse screw-thread; but the electric 

 current or lines of force, which it is designed to pick up 

 and carry, circulate at right angles to the axis of the core, 

 and extend to some distance beyond its surface. The prob- 

 lem thus presented is to wind around the soft iron a con- 

 ductor that shall be broad enough to grasp a large propor- 

 tion of this outspread force, and yet shall follow its course 

 as nearly as possible by standing out at right angles to the 

 axis of the armature. This he endeavored to effect by using 

 a core of square section, and winding round it a broad rib- 

 bon of sheet copper, insulated on both sides by cementing 

 on its surfaces a layer of silk ribbon. This armature was 

 laid with one edge against one side of the core, and carried 

 on thus to the angle; then turned over so that its opposite 

 edge should be presented to the next side of the core; this 

 side to be followed in like manner, the ribbon similarly 

 turned again at the next corner, and so on till the core be- 

 came fully enclosed or armed with the continuous ribbon, 

 which thus encircled the core with its edges outwards, and 

 nearly at right angles to the axis, in spite of its width, 

 which might be increased to any extent found by experi- 

 ment to be desirable. 



At this stage my direct co-operation and confidential 

 communication with Mr. Starr ceased, as I remained in 

 London while he went to Birmingham in order to get his 

 machinery constructed, and to apply it at the works of 

 Messrs. Elkington, who had then recently introduced the 

 principle of dynamo-electric motive-power for electro-plat- 

 ing, etc., and were, I believe, using Woolriclrs apparatus, 

 the patent for which was dated August 1, 1842, and en- 

 rolled February 1, 1843. 



I am unable to state the results of his efforts in Birming- 

 ham. I only heard the murmurs of the capitalists, who 

 loudly complained of expenditure without results. They 

 had dreamed the same dream that Mr. Edison has recently 

 re- dreamed, and has told the world so loudly. They sup- 

 posed that the mechanically excited current might be car- 



