25 8 ELECTRIC LIGHTING. 



rials is facilitated by the high temperature of places lighted by 

 gas. 



" The electric l ; ght, on the contrary, gives off extremely little 

 heat, since a lamp yielding a light equal to that of several hun- 

 dred stearine candles does not give more heat than a single 

 candle. 



"5. All the lamps supplied by the same dynamo-electric 

 machine are lighted up instantaneously." 



When only a portion of the space has to be lighted in a 

 given direction, and under an angle not exceeding 180 

 degrees, the diffusion projectors invented by J. Van Mal- 

 deren may be used with advantage. These consist of a kind 

 of parabolic mirror, of which the electric light occupies the 

 centre, and with the front part closed at a short distance 

 from the arc by a ground glass which receives the beam of 

 parallel rays sent out by the mirror, spreads them out so that 

 all the space in front is illuminated. It is stated that the 

 intensity of the illumination is greatly increased in this way. 



I think it will be interesting here to reproduce a letter by 

 Lontin relating to the divisibility of the electric light, which 

 has lately been so much spoken of, and has been put forward 

 as a new discovery, the anterior labours of Wartmann, Quirini, 

 and others being ignored. The letter was addressed to the 

 journal LJ Eledricite, and appeared in the number for 5th 

 November, 1878 : 



" Allow me to remind you that two years ago / took out a 

 patent for photo-electric regulators, which divide perfectly the 

 current supplied to them. 



" The Alliance electro-magnetic machine which was working in 

 the Exhibition, supplied, it is true, 4 Jablochkoff candles, but this 

 same machine, without any change, has worked 12 of my regu- 

 lators. Here, I think, we truly have the divisibility of the electric 

 light, a divisibility the more real since each of my regulators gave 

 a luminous intensity of 19 Carcel lamps. This luminous power 

 may, moreover, be yet further reduced, for I have obtained in- 

 tensities of only 4 Carcels. I think I may conclude from these 

 experiments that the Alliance machine, or one of my dynamo- 



