in Magnetism and Electricity. 97 



sesses all the properties of a permanent magnet, it appeared 

 reasonable to suppose that a large electromagnet excited by- 

 means of a small magneto-electric machine could, by suitable 

 arrangements, be made instrumental in evolving a proportion- 

 ately large quantity of dynamic electricity, notwithstanding the 

 pulsatory character of the electricity transmitted through the 

 wires surrounding the electromagnet. 



56. Two magnet-cylinders of similar construction to the one 

 already described (9) (figs. 1, 2, 3, 9), were therefore made, 

 having a bore of 2J inches and a length of Yl\ inches, or five 

 times the diameter of the bore. 



57. As frequent mention will have to be made of the different- 

 sized machines employed in these investigations, they will in 

 future be distinguished by their calibre, or the diameter of the 

 bore of the magnet-cylinder. 



58. Each cylinder was fitted with pillars, cross-heads, and an 

 armature similar to those already described (9, 10) (figs. 3, 6). 

 Around each armature was coiled an insulated strand of copper 

 wires 67 feet in length and 0*15 of an inch in diameter, the ex- 

 tremities of which were respectively connected with the two 

 halves of a commutator fixed on the axis of each armature (10). 

 Upon one of the magnet-cylinders (fig. 1) sixteen permanent 

 magnets, of the form shown in the figure, 1.2 inches in length, 

 were fixed. Each of the magnets weighed 3 lb., and would 

 sustain a weight of 20 lb. 



59. To the sides of the other magnet-cylinder, an end view of 

 which is shown in fig. 9, two rectangular pieces of boiler-plate, 

 0, 0, 12 \ inches long, 9 inches wide, and § of an inch thick, 

 were bolted parallel with each other and between the iron pack- 

 ings P, P, P', P'. The upper extremities of these plates were 

 united by means of a hollow bridge, Q, to which they were 

 bolted, along with iron packings similar to those on their 

 lower extremities. The bridge was made of two thicknesses of 

 the same boiler-plate iron as that of which the sides were made ; 

 and for the purpose of ensuring good contact, its edges, as well 

 as those parts of the sides of the rectangular plates in contact 

 with them and with the magnet-cylinder, were planed to a true 

 surface. An insulated strand of copper wires, 350 feet in length 

 and of the same diameter as that on the armature (58), was 

 coiled round each of the rectangular iron plates in a direction 

 parallel with the axis of the magnet-cylinder. The two coils 

 were united so as to form a single circuit 700 feet in length, the 

 free ends of which were furnished with suitable terminal screws 

 for the purpose of connecting them with the wires from the 

 2^-inch magneto- electric machine. A perspective view of this 

 machine is shown in fig. 10, but on a much larger scale than the 



Phil Mag. S. 4. Vol. 34. No. 228. Aug. 1867. H 



