272 LOCALIZED ELECTRIZATION. 



wire, rests upon a metallic ring fixed upon the reel. This ring is 

 divided into four teeth, two of which are very short. The second 

 spring of the rheotome S', which communicates with the other 

 extremity of the central wire, is brought in contact with the four, 

 or with the two teeth, by means of the regulating knob of the 

 commutator (not shown in tig. 64), which is fixed to the right 

 of the apparatus, and which turns from right to left, and vice 

 versa. 



F. — The regulator of the intermissions. 



A piece of copper is fixed to the base of the apparatus, to the 

 left of the large wheel. It is traversed by a screw, D, to which is 

 soldered a brass spring, T. By means of the screw D tlie s]3ring 

 I can be made to perform a to-and-fro movement, which brings it 

 in contact sometimes with the pins a, upon tlie posterior face 

 of the great wheel A, and sometimes with the plate G, which 

 supports the latter. One of the extremities of the inner (thick) 

 wire of the coil, and of the outer (fine) wire of the coil, communi- 

 cates with this plate G. The brass spring I is in relation, by a 

 copper wire, with the left side U, of the commutator of the 

 coils T. 



G. — Graduator of the currents. 



Two tubes of copper, H, H, covering the reels which are placed 

 under the arms of the magnet, and connected by a cross-piece at 

 their posterior extremity, are pulled out or pushed in, gliding over 

 the reels by means of the stem R. The latter, fixed to the cross- 

 piece, and terminating in a handle the length of the reels, is divided 

 into centimetres and millimetres. When pushed entirely within 

 the apparatus, the cylinders cover the reels, and the currents are 

 at their minimum of intensity. The currents are, on the con- 

 trary, at their maximum when the stem is drawn completely out of 

 the apparatus. Their intermediate degrees of force are in direct 

 proportion to the position of the stem. This stem, therefore, 

 merits the denomination of a graduator of tlie currents. 



H. — Commutator of the coils. 



The commutator of the coils, T, is constructed like that of my 

 volta-faradic instrument. 



§ II. — Theory of the Magneto-faeadic Apparatus. 



The simultaneous intermissions of the magnetic current, and of 

 that of the central coil produced by the rotary motion of the wheel 

 A, which puts in action the armature, and the rheotome, B, 



