I)U BOIS-REYMOND'S INDUCTOKIUM. 



551 



330. DU BOIS-REYMOND'S INDUCTORIUM MAGNETO-INDUCTION APPARATUS. 

 The inductorium of du Bois-Reymond, which is used for physiological purposes, is a modification 

 of the magneto-electromotor apparatus of Wagner and Neef. A scheme of the apparatus is 

 given in fig. 392. D represents the galvanic battery. The wire from the positive pole, a, passes 

 to a metallic column, S, which has a horizontal vibrating spring, F, attached to its upper end. 

 To the outer end of the spring a square piece of iron, e, is attached. The middle point of the 

 upper surface of the spring [covered with a little piece of platinum] is in contact with a movable, 

 screw, b. A moderately thick copper wire, c, passes from the screw, b, to the primary spiral 

 or coil, x, x, which contains in its interior a number of pieces of soft iron wire, **, i, covered 

 with an insulating varnish. The copper wire which surrounds the primary spiral is covered 

 with silk. The wire, d, is continued from the primary spiral to a horse-shoe piece of soft iron, 

 H, around which it is coiled spirally, and from thence it proceeds, at /, back to the negative 

 pole of the battery, g. When the current in this circuit called the primary circuit is closed, 

 the following effects are produced : The horse-shoe, H, becomes magnetic, in consequence of 

 which it attracts the movable spring or Neef s hammer, e, whereby the contact of the spring, 

 F, with the screw, b, is broken. Thus the current is broken, the horse-shoe is demagnetised, 

 the spring, e, is liberated, and, being elastic, it springs upwards again to its original position in 

 contact with b, and thus the current is re-established. The new contact causes H to be 

 remagnetised, so that it must alternately rapidly attract and liberate the spring, e, whereby the 

 primary current is rapidly made and broken between F and b. 



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Fig. 392. 

 I, Scheme of du Bois-Reymond's sledge induction machine. D, galvanic battery ; a, wire 

 from + pole, (g) - pole ; S, brass upright ; F, elastic spring ; b, binding screw ; c, wire 

 round primary spiral (x, x), containing (i, i) soft iron wire ; K, K, secondary spiral, with 

 board (p, p) on which it can be moved ; H, soft iron magnetised by current (d, f) passing 

 round it. II, key for secondary circuit, as shown it is short-circuited. Ill, electrodes 

 (r, r), with a key (K) for breaking the circuit. 



A secondary spiral or coil (K, K) is placed in the same direction as the primary (x, x), but 

 having no connection with it. It moves in grooves upon a long piece of wood {p, p). The 

 secondary spiral consists of a hollow cylinder of wood covered with numerous coils of thin silk- 

 covered wire. The secondary spiral, moving in slots, can be approximated to or even pushed 

 entirely over the primary spiral, or can be removed from it to any distance desired. 



[Fig. 393 shows the actual arrangement of du Bois-Reymond's inductorium. The primary 

 coil (R') consists of about 150 coils of thick insulated copper wire, the wire being thick to offer 

 slight resistance to the galvanic current. The secondary coil (R") consists of 6000 turns of 

 thin insulated copper wire arranged on a wooden bobbin ; the whole spiral can be moved along 

 the board (B) to which ,a millimetre scale (I) is attached, so that the distance of the secondary 

 from the primary spiral may be ascertained. At the left end of the apparatus is Wagner's 

 hammer, as adapted by Neef, which is just an automatic arrangement for opening and breaking 

 the primary circuit. When Neef's hammer is used, the wires from the battery are connected 

 as in the figure ; but when single shocks are required, the wires from the battery are connected 

 with a key, and this again with the two terminals of the primary spiral, S" and S"\ In the 



