INCANDESCENT LAMPS. 2OI 



seen, of a long and slender rod of carbon c c 2 millimetres 

 in diameter, supported on a heavy carbon-holder A, which 

 slides on a hollow column D between four rollers. This rod 

 rests on a cylinder of carbon R, turning on a horizontal arm 

 ^ fixed to the column. A guide, fitted with a brake F, en- 

 closes the rod of carbon to a short distance (6 millimetres 

 about) from the carbon cylinder, and at the same time con- 

 ducts to it the positive current, which returns to the gene- 

 rator by the carbon cylinder and its support. A second 

 brake F, placed behind the apparatus and resting on the 

 support A of the movable carbon through an opening made 

 in the tube D, moderates the action of the weight of the 

 support A, according to the degree of pressure exerted on 

 carbon disc R. For this purpose, the support of the axle of 

 this disc forms a rocker, and on the side of the rocker opposite 

 the disc R is fixed the second brake, of which we are speaking. 



The point of contact of the rod of carbon with the cylinder 

 is placed a little eccentrically, in relation to the vertical pass- 

 ing through the axis of the cylinder, so that at each lowering 

 of the system from the consumption of the rod, a small tan- 

 gential impulse may be given to the cylinder, which causes 

 it to make a slight movement that suffices to throw down the 

 ash accumulated at the point of contact. Without this pre- 

 caution, this ash might interfere with the brilliancy of the 

 light, at least with the impure carbons which are at present 

 in use. 



The problem which Reynier undertook to solve was, as 

 may be seen, to make a long slender rod of carbon incan- 

 descent towards its extremity, and while wasting at the end, 

 to be moved forward continuously and regularly. Fig. 52, 

 taken from the French patent of the iQth February, 1878, 

 dearly explains the data of this problem. 



" A cylindrical or prismatic rod of carbon c," says Reynier,* 

 *' is traversed between / and j by a continuous or alternative 



- See le compte rendu des stances de la Socittt dc Physique for April- 

 July, 1878, p 96. 



