OF ARTS AND SCIENCES. 227 



attached, at E and E', to two copper tubes, in the prolongation of 

 which, at C and C, the carbon conductors are fixed. A small lever, 

 movable by hand, carries a second nib similar to that of the small 

 lever, and serves to stop at will the motion of the apparatus. This 

 whole assemblage of parts is shut up in a metallic cover, the upper 

 part of which can be raised in order to display the pieces of the. inte- 

 rior mechanism. The following is the march of the current in the 

 regulator when the carbon points touch, or when the luminous arc is 

 not interrupted. 



" For this purpose, assume, as most physicists do, that the electri- 

 cal current advances from the positive to the negative pole, and 

 suppose that the positive pole of Bunsen's carbon battery is in 

 communication with the clamp R, and the negative pole with the 

 clamp E,'. The current, entering at R, descends through the wire g, 

 which an ivory ring insulates at I and i from the brass plate W W', 

 and from the plate and metallic columns which support the mechan- 

 ical parts of the apparatus. Running the whole length of the wire q 

 of the coil, the current passes into the iron plate F, which constitutes 

 the pole of the electro-magnet. The tube T, which carries the carbon 

 rod C, touches constantly this plate F, and continues the conduction of 

 the current, which, arriving at the place where the carbon points touch, 

 passes from one to the other, traverses the carbon rod C, ascends its 

 tube T', descends through the column S, and goes from this column 

 to the clamp R', which corresponds to the negative pole of the battery. 

 The column S is insulated from the rest of the apparatus by an ivory 

 ring P, in order that the current, to complete its circuit, may be forced 

 to go through the carbon rods. Things being thus disposed, the car- 

 bon points touching, or being removed by the distance best adapted 

 to the most brilliant arch of light, the plate F will be strongly magnet- 

 ized by the action of the current ; the iron K will be drawn into con- 

 tact ; its levers will rest against the toothed wheel r, and, even when 

 the spring in the wheel P is wound up, all will remain in equilibrium 

 in the interior of the apparatus. The electricity will continue to pass, 

 wasting the carbon C by the transfer of its molecules to the carbon C, 

 and both of them by their lively and rapid combustion in the air. 

 After a certain time, the carbon points will be so much separated that 

 the current experiences a considerable resistance in breaking through 

 the intervening space. The intensity of the current being diminished, 

 the spring s will destroy the contact of K ; its levers will discharge 

 their function ; the tooth d will quit the wheel r ; the main-spring will 



