34 



NA TURE 



[May 12, 1881 



into their greater mass and greater strength. We illus- 

 trate this idea in Fig. i. The City of London authorities 

 who have shown so much energy and commendable zeal in 

 carrying out this experiment would still further confer a 

 favour on the public if they were to remove their hideous 

 heraldric e.«rescence on the top of the so-called Temple 

 liar Memorial, and replace it by a handsome bronze 

 pillar 30 feet or 40 feet high carrying a bright and 

 iarilliant electric light. 



The Siemens system compares favourably with the 

 Urush system in one respect, and that is they do not 

 throw all their eggs into one basket. In their distributed 

 system they have arranged the lamps on two circuits, so 

 that each alternate lamp is on a diilerent wire, and if 

 anything goes wrong with the one circuit only alternative 

 lamps go out, and not all. With the Brush system, on 

 the contrary, if any fault occur in the wire in any of its 



length of nearly two miles, then every lamp on that circuit 

 must go out. 



The effect of fogs upon this system will be narrowly 

 watched. It may happen, and probably will, that the 

 fogs will be absolutely utilised by the electric light, for 

 the reflection in the neighbourhood of the light by the 

 small particles that constitute the fog throwing back the 

 rays of light will help to illuminate the street, and so to a 

 considerable e.xtent relieve the impression now produced 

 by dark fogs. 



Of the efficiency of the system, as v/e have said, there 

 can be no doubt. As to its economy, experience alone 

 can determine. That the firms therastlves require ex- 

 perience on this point is evident from the disparity in the 

 charges made by the two firms competing. The Brush 

 Company only estimate the cost of working their system 

 at 660/., which is the cost of gas : Siemens Brothers 



estimate the cost of working at 2270/, nearly four times 

 the cost of the Brush. We are inclined to think that a 

 mean must be taken between these two. It is hopeless 

 to expect that electric lighting in every case can be done 

 at the cost of gas. Electric lighting is a luxury, and as a 

 luxury we must expect to pay for it. Nevertheless it must 

 not be forgotten that gas utilised as a motor can produce 

 eleven times the quantity of light by the aid of electricity 

 than it produces by direct combustion. This calculation 

 is interesting. One hundred cubic feet of gas per hour can 

 be made by combustion to produce 300 candle-power. The 

 same quantity of gas used in a gas-engine to rotate a 

 dynamo-machine will produce a light equal to 3750 

 candles, an illuminating power twelve times greater. Hence 

 there must also be some cases in which the electric light 

 can economically supplant gas ; whether it can do so in 

 the case of street-lighting remains to be seen by the great 

 experiment now being tried. 



There are two or three very interesting points on the 



line of illumination where comparisons can be made 

 between the difterent systems. For instance, from the 

 middle of Blackfriars Bridge there is a good comparative 

 test between the Brush and Jablochkoft' systems ; while 

 at the corner of King Street there is an equally excellent 

 opportunity to examine the merits of the Siemens distri- 

 buted and the Brush systems. Photometric measure- 

 ments at each place prove that the Brush Company's 

 estimate of the light power of their lamps is absurdly 

 exaggerated; 750 candles would be a very fair figure 

 to give the lamp. The unhesitating opinion is that 

 comparing each individual lamp, the Brush surpasses the 

 others. In fact there is little difference between the smaller 

 light of Siemens and the Jablochkoff, excepting this, that 

 the Jablochkoft', by its variation and pinkish effects, irri- 

 tates the eye considerably, although in bright weather the 

 effect on the water is sparkling and brilliant. The Jabloch- 

 kofif system has been entirely put in the shade by this 

 interesting experiment. Though however we are obliged 



