May 19, 18S1J 



NATURE 



61 



current, is rendered highly incandescent, chiefly however 

 at that part near the copper electrode, where the pencil 

 becomes pointed, and therefore more intensely heated. 

 There is also, in addition to this, a glow or flame-like 

 appearance from the sides of the consuming carbon to 

 the copper electrode, the light thus apparently taking an 

 intermediate position between the purely incandescent 

 system and that of the arc. The heated point of carbon 

 becomes curled at the tip in a peculiar manner, as though 

 it were viscous in shape, somewhat like a mushroom 

 where it wastes away, and is replaced by the gradual 

 forward motion of the pencil. 



The fi.xed electrode, which may be entirely of copper 

 or with a graphite insertion, remains intact without any 

 appreciable wear. 



The chief improvements in this lamp consist in the 

 simplification and certainty of action of the mechanism in 

 connection with the contact jaws for clamping the carbon 

 pencil, by which means the lateral pressure of the jaws 

 and the feeding of the carbon are attained by the com- 

 bined action of one actuating weight, as shown in the 

 diagram, Fig. 5. It will be seen from this that the lateral 

 pressure is thus always proportional to the downward 

 pressure, and may be varied to suit any conditions. The 

 details devised for rendering the lamps in the same circuit 

 independent of each other, and its general adaptability 

 for interior and domestic lighting, constitute an important 

 advance on anything which has gone before. 



On referring 10 the sectional view of the lamp. Fig. 5, 

 E is the fi.\ed copper electrode upon which abuts the point 



Fic. 3. 



of the carbon e, which is rendered intensely incandescent 

 by the passage of the current between the jaws and the 

 copper cylinder. The jaws are shown at J clamping the 

 carbon pencil. The actuating weight, w, which gives 

 both the feeding motion to the pencil as it consumes, and 

 the lateral pressure to the jaws, is suspended by continuous 

 cords to the top of the lamp E, the cords then passing 

 down through the weight and under one of the rollers at R, 

 up again through a roller attached to the carbon holder, 

 then back again through another roller at R, and ending 

 at the weight. The rollers R are attached to a light tube, 

 P, which passes down through a nipple, N,and terminates 

 in a flange under the horizontal arms of the jaws and lifts 

 them according to the leverage, thus producing the lateral 

 pressure on the pencil. The top of this tube has also 

 attached to it the armature, A, of an electro-magnet _S, 

 wound with fine wire and arranged in a shunted circuit in 

 such a manner that as long as the normal condition of 

 the light is maintained it is neutral ; but if an arc should 

 be accidentally formed between the carbon c and the 

 copper E, the tlectro-magnet comes into action in opposi- 

 tion to the controlling weight, and frees the jaws from 

 lateral pressure, thereby allowing the carbon pencil to 

 descend freely and establish contact. 



The carbon-holder is also arranged (Fig. 6) so that 

 when the pencil is very nearly consumed the lamp is 

 automatically short-circuited by the lever at L making 

 contact with the arm carrying the copper electrode. 



The stem or body of the lamp forms an important part 

 of the whole, being formed of metal tubing in two semi- 



circular halves, each half forming part of the electrical 

 circuit, the current traversing one side, of which the jaws 

 form part, passing through the carbon pencil to the copper 

 electrode, and returning by the other side of the lamp. 



The two sides are kept closed mechanically (but insu- 

 lated electrically from each other) by the latch and knob 

 T, Fig. 5, which also automatically short-circuits the lamp 

 when opened for the purpose of putting in fresh carbon, 

 thus rendering it perfectly safe in handling. There are 



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M, 



ingenious arrangements attached to this system for 

 switching a lamp on or off, with resistances equivalent to 

 that of the lamp ; but upon these it is unnecessary to 

 dwell, these adjuncts being common to many systems. 



Prof. Adams stated at the Society of Arts that with this 

 system an illuminating power of 715 candles per horse- 

 power could be obtained. 



If incandescent lighting is more expensive than the 



