100 Mr. H. Wilde^ Experimental Researches 



plete is shown in fig. 10. Each side of the electromagnet O/O, 

 fig. 9, is made of a plate of rolled iron 48 inches in length, 39 

 inches wide, and 1^ inch in thickness. The wrought-iron bars 

 P, P, P', P', bolted to the upper and lower extremities of the 

 plates, are 6 inches wide and 2 inches thick. These bars are 

 somewhat longer than the width of the plates, and are secured 

 to the sides of the magnet-cylinder, with the plates between 

 them, by means of iron bolts 1 inch in diameter. The bridge 

 Q extends the whole length of the bars P', P ; , and is made of 

 two plates of rolled iron 43 inches long, 16 inches wide, and 

 \\ inch thick, separated from each other by an iron packing 

 3 inches in thickness, which makes the entire depth of the 

 bridge equal to the width of the bars P', P\ The bridge is 

 fixed between the side plates by means of long iron bolts 1 inch 

 in diameter, extending from one side of the magnet to the 

 other, as shown in the figure. All the component parts of the 

 electromagnet which required to be fitted together were planed 

 to a true surface, for the purpose of ensuring intimate ferric 

 contact throughout the entire mass. The total weight of the 

 iron of the electromagnet, exclusive of the magnet-cylinder, is a 

 little more than 1*5 ton. 



68. Each side of the electromagnet was coiled with an insu- 

 lated conductor, consisting of a bundle of thirteen No. 11 cop- 

 per wires, each 0*125 of an inch in diameter, laid parallel with 

 each other, and bound together with a double covering of linen 

 tape, after the manner adopted by Joule in the construction of 

 his electromagnets*. The length of conductor coiled round 

 each side of the electromagnet is 2400 feet, and the outer extre- 

 mities of the coils are coupled up so as to form a continuous 

 circuit 4800 feet in length. The inner extremities of the coils 

 terminate in two insulated metal studs fixed upon the wooden 

 top of the machine (fig. 10). The total weight of the two coils 

 is 1*3 ton. 



69. The magnet-cylinder consists of two masses of cast iron 

 50 inches in length, separated from each other by an interval of 

 5 inches by means of blocks of brass placed at intervals along 

 the top and bottom of the cylinder. All the fiat surfaces of the 

 latter, as well as those of the brass blocks in contact with them, 

 are truly planed, and the several parts of the cylinder are bolted 

 together at the top and bottom by means of twelve copper bolts 

 1 inch in diameter. The bore of the magnet-cylinder is 10 

 inches, and its weight, when fitted up with iron pillars and brass 

 cross-heads, is 1*1 ton. 



70. The machine is furnished with two armatures — one for the 

 production of " intensity," and the other for the production of 



* Annals of Electricity, vol. v. p. 472. 



