102 
MR. H. WILDE’S EXPERIMENTAL RESEARCHES 
(figs. 1, 2, 3, 9), were therefore made, having a bore of 2£ inches and a length of 121 
inches, or five times the diameter of the bore. 
57. As frequent mention will have to be made of the different-sized machines em- 
ployed 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 0T5 of an inch in diameter, the extremities 
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 perma- 
nent magnets, of the form shown in the figure, 12 inches in length, were fixed. Each 
of the magnets weighed 3 lbs., and would sustain a weight of 20 lbs. 
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, O, O, 12-J inches long, 9 inches wide, and 
§ of an inch thick, were bolted parallel with each other and between the iron packings 
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 magneto-electric machine which is placed on the top of it. The 2^-inch 
magneto-electric and electro-magnetic machines were placed side by side upon a strong 
wooden base, and their armatures were driven simultaneously from the same driving 
shaft, at an equal velocity of about 2500 revolutions per minute, 
60. Experiments were then made for the purpose of comparing the quantities of elec- 
tricity evolved from the magneto-electric and electro-magnetic machines, as measured, 
approximately, by their heating effects. When the alternating waves from the mag- 
neto-electric machine were transmitted through a piece of No. 20 iron wire, 0 - 04 of an 
inch in diameter, a length of 3 inches of this wire was raised to a red heat. 
61. The direct current (15) from the magneto-electric machine was then transmitted 
through the coils surrounding the iron plates O, O, which being united by the bridge 
Q, formed a powerful electro-magnet similar in construction to that invented by Joule*, 
and having for its poles the two sides of the magnet-cylinder. When the alter- 
* Philosophical Magazine, S. 4. vol. iii, p. 32. 
