[Illustration: Fig. 35. II. Hoof Shod with Shoe provided with Toe-piece and Calkins; Wall of the Hoof covered with Tinfoil. a, Heel angle, with b, the contact-screws; c, screw-clamp, with contact-spring (isolated from the shoe); c' conducting-wire from the same; d, screw-clamp, with conducting-wire (d') screwed into the edge of the shoe; e, nails isolated by cutting a small window in the tinfoil.] [Illustration: Fig. 35. III. Hoof Shod with Plain Shoe; Horny Wall covered with Tinfoil. a, Toe and heel angle, with b, the contact-screws; c, conducting-wire passing from the tinfoil on the wall; d, conducting-wire passing from the shoe; c', d', ends of the conducting-wires, which must be imagined connected with the ends c', d', passing from the apparatus.] It is unnecessary for our purpose here to minutely describe the exact _modus operandi_ of these two experimenters. Briefly, the method of inquiry adopted in each case was the 'push and contact principle' of the ordinary electric bell, and the close attention which was paid to detail will be sufficiently gathered from Figs. 35 and 36. [Illustration: Fig. 36. I. LEFT FORE-FOOT SHOD AND MOUNTED TO RECOGNISE THE SINKING OF THE SOLE. _a_, Iron plate covering the inner half of the horny sole; _b_, openings in the same, with screw-holes for the reception of the contact-screw _c_ (the part of the sole under the plate is covered with tinfoil, which at _d_ passes out under the outer branch of the shoe, and becomes connected with the tinfoil of the wall; in order to give the freshly applied tinfoil a better hold, copying-tacks are at _e_ passed through it into the horn, and one is similarly used to protect the tinfoil at the place where the contact-screw touches the latter); _f_, holes with screw thread for the fastening of the angle required to measure the movement of the wall, and also for the fastening of the conducting-wire, _g; h_, conducting-wire passing from the tinfoil; _i_, isolated nails.] [Illustration: Fig. 36. II. BAR-SHOE WITH OPENINGS. _a_, Near the inner margin and in the longitudinal bar; _b_, for the reception of the contact-screw _c; d_, openings for fastening the angle and the conducting-wires.] After numerous experiments with the depicted contact-screws, moved to the various positions indicated in the drawings, the following conclusions were arrived at: