Upon the electrical experiments to determine the location of the bullet in the body of the late President Garfield; and upon a successful form of induction balance for the painless detection of metallic masses in the human body . was at once tested in my laboratory, with re-sidts sliglitly hettei than tliose I had (thtained in Boston. My Boston apparatus did n«)t give a greater heaiing dis-tance than 3 cm., whereas with the Hopkins apparatus 1 coulddistinguish effects at a distance of cm. Two of Mr. Hopkins coils (A B, Fig. 2) were then fas-tened npon a wooden handle to form an exploring
Upon the electrical experiments to determine the location of the bullet in the body of the late President Garfield; and upon a successful form of induction balance for the painless detection of metallic masses in the human body . was at once tested in my laboratory, with re-sidts sliglitly hettei than tliose I had (thtained in Boston. My Boston apparatus did n«)t give a greater heaiing dis-tance than 3 cm., whereas with the Hopkins apparatus 1 coulddistinguish effects at a distance of cm. Two of Mr. Hopkins coils (A B, Fig. 2) were then fas-tened npon a wooden handle to form an exploring instiument,and the whole apparatus was arranged for innnediate use incase of any necessity arising for an experiment npon the Pres-ident. I set myself in connnunication with Mr. Hopkins, andrequested his assistance and co-operation, and in reply receivedtln-ougli Private Secretary Bi-own tlic following account offurther experiments : Fig. a. (»0 Irving Place, Brooklvn, -A//// IB, 1 Mr. J. Stanlev Brown : Dear Sir : I liavu made two new instruments on plane ing from that sent, hut they yield no l)ettei- results. T consisted of two ol)longcoils a r - range d at right angles to each oth- er, tluis : 881. ^difler-iie tirst. The outer coil being of coarse wire (No. 18) placed in the primary circnit, the inner coil l)eing of very tine wire (No. 36) ami connected with a telephone. The parallel cm-rents traversing the wires neutralized each otlier, and no audible effects are perceived in the telephone, but on presenting a metallic hody to the instrument npon a line bisecting the angle between the coils the clicking in the telephone is heanL This instrument possesses only one advantage ovci that^ sent, and that is that it requires no adjustment. See Ajipeudix, notes .\ uiul 1. The other iii^truiuent consists of two Lu-) phiced upon opposite sides of a coil of coarse wii-e, (No. 1^,) tlie fine coil Ueiiiii connected so that the induced cnn-ents ncnti-alizc each othei, tluis: Fig. 4,. I
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