ELECTRIC LIGHTING, PROGRESS OF. 



303 



higher temperatures safely. These lamps are 

 being continually improved in this direction, 

 the lamps of to-day being very much better 

 than those of .a year or two ago. 



Two new lamps of this kind have recently at- 

 tracted considerable attention, though they do 

 not appear to possess any advantage over pre- 

 vious ones. In one of these the light-giving 

 carbon is in the form of a hollow tube, and in 

 the other it consists of a platinum wire with a 

 carbon coating. The former of these is the in- 

 vention of Mr. Alexander Bernstein, of Boston, 

 and the latter of Signor Cruto, of Turin. In 

 manufacturing his tubular carbons Mr. Bern- 

 stein at first carbonized straws, and later de- 

 posited carbon from a carbonaceous gas or 

 liquid upon a metal mandrel, which latter was ' 

 afterward dissolved out by acids. This method 

 was, however, abandoned, and the carbons 

 formed by wrapping paper about a rod, the 

 successive layers of paper being made to adhere 

 by gum or paste. These paper tubes were then 

 carbonized, in the ordinary way. Owing to the 

 great shrinkage undergone by them in process 

 of carbonization, the paper was finally replaced 

 by a closely-woven textile fabric of cotton or 

 silk. The inventor has been able to produce 

 his tubes in the form of a bow, so that in ex- 

 ternal appearance his lamp does not differ ma- 

 terially from those now in use. These carbons 

 are said to be highly elastic, so much so that 

 they can be bent nearly straight, and will spring 

 back to their normal shape. The lamp differs, 

 further, from present lamps in being of quite 

 low resistance, which will prohibit its use in 

 any extensive multiple-arc system of distri- 

 bution. The inventor, however, contemplates 

 placing them in series as is done with arc-lamps. 

 At the recent Exhibition of Electricity, at Vi- 

 enna, a number of these lamps were shown of 

 65 and 150 candle-power. The appearance of 

 the lamp is shown in Fig. 1. 



The filament of the Cruto lamp is made by 

 raising a platinum wire to incandescence in a 

 carbonaceous atmosphere, the carbon being de- 

 posited upon the wire in the same way as it is 

 upon carbon filaments in the " treatment " to 

 which these are subjected by some of their 

 makers, to render them homogeneous. An- 

 other incandescent lairp of a decidedly novel 

 character has been patented in England by 

 Messrs. Boullon, Probert, and Soward, though 

 it does not appear to have been publicly shown 

 in operation as yet. Instead of first making 

 the filament and then mounting it upon lead- 

 ing-wires and sealing them into a glass globe, 

 as is done in all other lamps, these inventors 

 manufacture their filament by means of the 

 current after they have sealed the leading- 

 wires in place in the globe. To this end they 

 introduce two platinum wires in a glass en- 

 velope, the inner ends of these being the dis- 

 tance apart of the intended length of the fila- 

 ment. A carbonaceous gas is then introduced 

 into the globe, and a carbon bridge built across 

 from one wire to the other by passing electric 



sparks between the platinum electrodes. The 

 inventors state that they are able by this means 

 to produce a carbon filament of great purity, 

 and one which, being formed under the influ- 

 ence of the current, is not disintegrated by the 



FIG. 1. 



prolonged action of the current upon it. The 

 apparent objection to forming a filamentary 

 conductor in this way is the difficulty of ob- 

 taining a filament of uniform section, which is 

 essential to permanence, as otherwise there will 

 be spots throughout the conductor at greater 

 temperature than the remaining portions, and 

 the filament will tend to give way at these 

 points of greater strain. 



In dynamo-machines, though new varieties 

 continue to be brought out, there is but little 

 of importance to chronicle. An improvement 

 in the 'construction of dynamos for incandes- 

 cent lighting has, however, been patented dur- 

 ing the year by Mr. Edward Weston, which 

 deserves notice here. As is well known, in- 

 candescent lamps are arranged in what is 

 termed multiple arc that is, one terminal 

 of the lamp is connected to the outgoing and 

 the other to the return conductor. Each 

 lamp, therefore, takes its own supply of cur- 

 rent independently of all the rest. In order, 

 however, that the proper amount of current 

 should pass through each lamp, the electro- 

 motive force of the current should remain 

 constant, however the amount of the current 

 varies as lamps are turned off and on that is, 

 the difference of potential between the termi- 

 nals of the machine must be unvarying. Mr. 

 Weston succeeds in fulfilling this condition by 

 establishing a certain relation between the ar- 

 mature and the field. 



As is well known, the brushes of a dynamo, 

 instead of resting upon the commutator at 





