496 



NATURE 



{April 1 8, 1878 



electric reservoir, which is composed of glass plales and Liii-ioii 

 laid side by side alternately. 



The condenser, however, is not charged direct by the battery, 

 but the current is made to work this Ruhmkorff induction coil, 

 from which there is derived a current having an enormously 

 increased electromotive force, and it is this electricity that is 

 stored up in the condenser. 



Having charged the condenser in this fashion, the whole of the 

 electricity is at once sent through the line, and produces most 

 extraordinary results. So much, then, for the lighting of the 

 gas. The process of turning on and off the gas, although 

 involving many important details, is very simple. Mr. Fox 

 makes use of the soft iron core which runs through the centre of 

 the coil to produce a reciprocating horizontal motion of a per- 

 manent horse-shoe magnet, suspended on needle-points just 

 above the coil. The soft iron core with the primary coil is, in 



Fig. 5. 





Fi0.6. 



fact, an electro-magnet, which can be magnetised so as to render 

 its ]ioIes reversible at pleasure ; the magnets are carried in a 

 small metal frame, having a passage through it for the gas to 

 pass to the burner at the top, and being provided with a stop- 

 cock, or valve, which is actuated by the reciprocating magnet. 

 The whole of this apparatus is inclosed in an air-tight metallic 

 case, which measures about 2,^ inches high, by 2^ wide, and is 

 screwed on to the supply-pipe in the lamp, the insulated con- 

 ductor or line- wire being carried down the interior of the lamp- 

 post and laid under ground, except, of course, where an overhead 

 line is admissible. The turning of the gas on and off is accom- 

 plished by opening and closing what may be termed an electric 

 needle-tap. The plug of this needle-tap is cylindrical, and 

 about a quarter of an inch in diameter, and is carried in a 

 socket, which it fits rather loosely. It is made to turn in this 

 socket by the action of the reciprocating magnet, a couple of 

 studs, which are brought into contact with a small pin or 

 lever connected with the plug, and forming, in fact, the handle 

 of the stop-cock. The annular space between the plug and the 

 socket (which is about one-thousindth part of an inch) is filled 

 with some liquid, which is retained by capillary attraction 

 bttween the two surfaces, the joint being thus rendered perfectly 

 gas-tight. The oil of bitter almonds or glycerine are both well 

 adapted for this purpose, on account of their non-oxidisable 

 character, and from the power they possess of resisting the action 



Tig. 7. 



Fig. 9. 



oi very low temperatures. A special feature in the apparatus is 

 the introduction of a fixed core, which can be magnetised, so as to 

 render its poles reversible at pleasure, and in conjunction with 

 it a movable magnet, the polarity of which is permanent. An 

 electric current sent either forwards or backwards for a i&w 

 seconds will turn the gas on or off in every lamp in the circuit 

 according to the direction of the current. 



To put the system into practical operation, there would be for 

 any district of, say two or three thousand lamps, a central sta- 

 tion, from which the wires would proceed in every direction, so 

 as to command a number of distinct circuits ; all that is necessary 

 to have at the central station would be a battery of some sort. 

 Mr. Fox would much prefer a magneto-inductor. By means 

 of a switch and a commutator the electric current from this 

 machine can be directed so as to operate separately on each one 

 of the circuits, and by this means turn the gas on or off. When 

 the gas is turned on it is lighted by sending a discharge from the 

 condenser. It is constructed of alternate metallic plates, with 



an iiitulalor or dielectiic between ihtm ; the conducting surfaces 

 in this cage are of tinfoil, apd the dielectric of crown glass. The 

 coil used for charging the condenser need not give more than 

 about three-quarters of an inch spark in the air. The discharge, 

 like the current, will of course have to be sent through each 

 circuit separately, and this is also done by means of the switch 

 arrangement. 



The accompanying figures will enible the reader more clearly 

 to understand the description we have given above. 



Fig. I is a front elevation. Fig. 2 a side elevation, and Fig. 3 

 a plan of the apparatus ; Fig. 4 is a plan of the permanent 

 magnet ; Figs. 5 to 9 represent details to be rtfened to. 



JFlG. 10. 



a is the gas-pipe leading from any ordinary source of supply ; 

 <5 ^ is a rectangular frame of white mttal or brass, cast or made 

 with a hollow core, and having two cylindrical portions, c J. 

 The part d\% screwed upon the gas-pipe a, which supports the 

 apparatus, and the part c receives the stop-cock ; this cock, 

 which is shown in sectional elevation in P'ig. 5, and in sectional 

 plan in Fig. 6, is composed of a brass tube e (shown separately 

 in Fig. 7), which fits into the cylindrical part c, and has two 

 openings,//, corresponding with the passages gg, in the ojipo- 

 site sides of the frame bb ; h is the plug of the cock (shown 

 separately in Fig. 8) ; it is made with a very slight downward 

 taper, and has two apertures or ways «/,. corresponding with the 

 openings// in the tube e, and it is hollowed out in the middle. 

 When the gas is turned on, the apertures i i come opposite the 



