ELECTRIC LIGHTING, PROGRESS OF. 



269 



and of inequality in the carbons, there is that 

 due to the shifting of the arc from one point 

 to another on the surface of the electrodes. If 

 the carbons could be very thin rods, the arc 

 would always form at practically the same 

 points, and irregularity from this cause would 

 be inappreciable. The electrodes must, how- 

 ever, be of considerable size to avoid too rapid 

 consumption, and this difficulty, therefore, ap- 

 pears to be inherent in the practicable form of 

 this lamp. The cost of lamps of this type is 

 also very considerable, even with the quite sim- 

 ple regulating mechanism now used in the best 

 forms. In view of these considerations, it may 

 be questioned whether the abandonment of 

 this type of incandescent lamps has not been 

 premature, and whether we shall not yet see 

 a return to it. Though the amount of light 

 yielded by regulators be greater for a given ex- 

 penditure of power, it does not, therefore, fol- 

 low that the equal illumination of a given area 

 will be less costly by them, as it is very well 

 understood that any quantity of light properly 

 distributed gives a more effective illumination 

 than a much greater amount at a few centers. 

 M. Emile Reynier, one of the earliest invent- 

 ors of this type of lamp, has 

 recently returned to the sub- 

 ject, and has succeeded in 

 producing a lamp free from 

 the objections of the older 

 forms, and of such extreme 

 simplicity as to leave noth- 

 ing to be desired on this 

 score. In his former lamp, 

 a carbon pencil resting upon 

 an abutment was fed con- 

 tinuously, by means of a 

 weight or spring, past a 

 heavy carbon contact, the 

 portion of the pencil be- 

 tween this contact and the 

 abutment being incandes- 

 cent. This construction 

 presented mechanical diffi- 

 culties to the regular feed- 

 ing that were not satisfac- 

 torily overcome, and the 

 contact interfered with the 

 economy by conducting away 

 the heat. In the present 

 lamp two pencils are used, 

 inclined but slightly to each 

 other, so that they touch 

 at a point a short distance 

 from their points, which 

 rest upon small abutments 

 of copper. The contact 

 which limits the incandes- 

 cence is therefore a hot con- 

 tact, and hence no heat is 

 FIG. i. wasted by its means. The 



form of the lamp is shown 

 in Fig. 1. The carbons, A B, are forced down- 

 ward by the weights, P Q, sliding upon the me- 

 tallic guides, C D. The abutments, E F, are of 



copper, attached to the bronze arcs, G II. The 

 two halves of the lamps are connected by the 

 insulated clamps, I and J. The weights, P and 

 Q, are insulated from the carbons, which they 

 impel by the caps, r and s. The current en- 

 ters by the terminal, K, follows the brass 

 guide, C, the arm, G, the abutment, E, and the 

 pointed end of the carbon, A, to the contact, #, 

 at which point it crosses over to the carbon, B, 

 and descends through the abutment, F, and 

 passes out by the arm, H, and guide, D, to the 

 terminal, L. No thorough tests have yet been 

 made of this lamp, but M. Reynier states that 

 the results of experiments so far conducted 

 are very satisfactory. The disadvantage of all 

 lamps of this type is the necessity of using 

 very large conductors, as, owing to the small 

 resistance of the carbon-pencil, it requires a 

 current of great strength to bring it to the 

 proper incandescence. Such lamps can not, 

 therefore, be worked economically upon long 

 circuits, but in separate installations, such as 

 the lighting of workshops, this objection is 

 evidently of but small moment. The same 

 inventor has also devised an incandescent lamp 

 in which he has attempted to obtain a sufficient 

 resistance without resorting to a filamentary 

 conductor, such as is used in all the other well- 

 known incandescent lamps. This increased 

 resistance is obtained by cutting the carbon- 

 rod, which serves as the light-giving portion, 

 several times across, or by notching it. This 

 conductor is inclosed in a glass globe, exhaust- 

 ed or filled with a gas which does not unite 

 chemically with the carbon. 



New arc-lamps continue to multiply, but 

 nothing of special importance has made its 

 appearance during the year. This lamp has 

 now reached such a condition that improve- 

 ments to be expected in it are of a kind hav- 

 ing a manufacturing value chiefly such as will 

 decrease the cost of production, and increase 

 its serviceableness in use. 



In the matter of generators two new dynamo- 

 machines have lately been brought to the atten- 

 tion of the public in England : one is the inven- 

 tion of Mr. J. E. H. Gordon, and the other 

 that of Sir William Thomson and Mr. Ferranti. 

 This latter was very much talked of previous 

 to being exhibited ; but the extravagant expec- 

 tations in regard to it can hardly be said to have 

 been realized. It is an alternating machine, as 

 is also the Gordon, and on this account it is of 

 but minor importance; for, it is quite safe to 

 say that machines of this class will find but a 

 limited use in the industrial development of 

 electrical appliances. Its merit lies in the great 

 simplicity of its armature, and consequent low 

 cost of manufacture. The armature- wires, in- 

 stead of being wound on a drum, as in the 

 Siemens, or over a ring, as in the Gramme, are 

 in the form of a zigzag on the face of a cen- 

 tral disk, revolving in a magnetic field made 

 up of a number of electro-magnets. The dis- 

 position of armature and field is shown in Fig. 

 2, in which the dark line represents the arma- 



