538 



SCIENCE. 



THE ELECTRIC EXPOSITION. 

 The Electric Light, 

 the generators. 



Th° Palace of Industry offers to the world a unique 

 collection of apparatus tor producing the electric 1 ght. 



The problem seems to be solved, if we can judge by 

 the multiplicity of the solutions proposed ; we shall see. 

 in the sequel that it is not yet completely solved, but this 

 same multiplicity sets out well in relief the incomparable 

 elastici'y of electricity applied to 1 ght, and sho^s ihat it 

 is possible from this day to introduce the electric light in 

 all appl cations; by gvmg to it, in each particular ca-e, 

 the special qualiies which assure its superiority over 

 other systems, under the limitation of two conditions 

 which we shtll treat separately : economy and the distri- 

 bution of electricity. 



We shall rap.dly examine the processes of gen- 

 erating el-ctrici y tor the special purpose of light ; a fol- 

 lowing article will be devoted to lights, regulators, and 

 incandescent lamps. 



Three methods are known of generating electricity in 

 quantity sufficient for the electric 1 ght : hydro-electric 

 piles, thermo-electric piles, and electro-dynamic 

 machines. 



In this Exposition there is no thermo-electric pile 

 applied to light. Some vears ago we had h jped that M. 

 Clamond would have continued his work in thermo- 

 electricity, but he has, unfortunately, done nothing, and 

 we can only express our r-gtets in this respect. 



The piles intended for the electric 1 ght are represented 

 at the Exposition but by two types: the pile of M. Cloris 

 Raudet and that of M. Tommasi. 



The p le of M. Cloris Baudet is a pile with b : chromate 

 of po ash ; with five elements, of which, according to the 

 inventor, only one a day neecs to be replaced, the pile 

 can sustain a voltaic arc, wi h carbons ot three millime- 

 tres, whose power is about 15 Carcel burners. 



The pile ot M. Tommasi is a Bunsen pile. The im- 

 provements which have been applied to it do not appear 

 fortunate to us, and we do not yet know of an app.ication 

 whrre it serves in a practical manner for domestic usage, 

 as the prospectus pompously announces it. It is only 

 necessary to approach for a moment the expos tion of 

 M. Tommasi, on the ground floor, in order 10 fee/— in 

 the proper and in the figurative sense — that the vapor 

 of liberated hypoazotic acid make; the pile absolutely in- 

 applicable to the usage for which it was primitively 

 intended. 



The instalment of this extensive apparatus and the 

 manipulation which it requires, are. on the other hand, 

 out of proportion with the r suit ob ained. 



Leaving aside these two separa e cases, and the elec- 

 tric accumulators, to which we shall return, we can say 

 that the electric light ot ihe Palace is exclusively obtained 

 from mechanical generators of electricity. 



The motors which drive the eltctric machines demand 

 a special study. They are of two kinds: steam and gas. 



The Exposition contains several interesting types of 

 motors especially intended to drive the electro-dynamic 

 machines ; we will cire among others the Brotherhood 

 motor and the Dolgoronki rotative system motor. In 

 these systems of motors of great rap dity, the driving 

 shaft ot the electric machine lorms the prolongation of 

 that of the motor ; thus all intermediate transmiss.on is 

 done away with, but simplicity is purchased, it must be 

 admitted, by a greattr expenditure of steam. 



The largest part of the motive force is produced by 

 fixed, half-fixed, or movable machines varying from five 

 to 150 horse-power. We c)o not say that ihe latter are 

 most economic, because they consume, with equal power, 

 much less ol carbon, and because ihey have also a more 

 regular motion — an essential condition for a good electric 

 light. 



We will notice more particularly two types of these 

 powerful machines : one, exhibited by MM. Carels, 

 is an expansion-engine, in a single cylinder ; the 

 other, exhibited by MM. Weyher and Richemond, belongs 

 to the compound type, that is to say, with a compound 

 cylinder; the expansion is made successively in the two 

 cylinders. Figure 7 represents this motor driving the 

 electric generators with alternate currents of Gramme 

 and Lambotte-Lachaussee. The advantage ot expansion- 

 engines, either with one cylinder or with two conjugate 

 cylinders, is great, for as soon as 100 horse-power is 

 reached, less than a kilogramme of carbon is consumed 

 each hour for every horse-power. 



A large number of gas motors are also used to produce 

 motive force. Most of them belong to the Otto type ; 

 they vary from 1 to 50 horse-power. The gas motors 

 are practical enough, and also, up to a certain point, 

 economical, when they serve to produce a light for a few 

 hours each day, and in an intermittent manner. 



For the same quantity of gas consumed, we can obtain 

 10 or 15 limes more light by passing through the medium 

 of the motor, the electric generator and the lamp, than 

 by directly burning the gas in the ordinary burners, all 

 in producing 100 or 150 times less heat in the light. 



It is by an 8 hotse-power gas motor that M. Jaspar 

 drives the three Gramme machines which feed the three 

 regulators placed in hall XV ; a 50 horse-power gas 

 mo 1 or also serves to light a part ot the Palace. 



We now come to the machines. We can first divide 

 them, according to the generally admitted classification, 

 into magneto-electric machines, of which the inductors 

 are magnets, and into dynamo-electric machines, of 

 which the inductors are electro-magnets. 



The Exposition contains only two kinds of magneto- 

 electric machines, the old type of Alliance and the ma- 

 chine of M. de MeVitens. These machines are applied 

 to beacon lights, and they also feed several Berjot regu- 

 lators. Without wishing to condemn the electro-mag- 

 netic machines, it seems 10 be established, even by the 

 Exposition, that their industrial reign has terminated. It 

 must not be concluded by this that the electro-magnetic 

 machines are worthless, but only that they are not indus- 

 trial, in the practical sense ot the word; that is to say, the 

 power being equal, they are heavier, more expensive, and 

 more encumoenng than the electro-dynamic machines 

 which are almost universally employed to-day. 



In light-houses, where the question of capital engaged 

 plays but a secondary role, the piefcrence has been given 

 to magneto-electric machines which, in consequence ot 

 the masses put in motion, give a greater relative regu- 

 larity than electro-dynamic machines. 



Magneto-electric machines, applied to light, are all 

 with alternative currents. 



Dynamo-electric machines are divided into two classes, 

 according as they furnish alternative or continuous cur- 

 rents. 



Machines with continuous currents. — The machines 

 with continuous currents are suited to illumination by ihe 

 voltaic arc and by incandescence. When they supply a 

 single light they are mounted as represented in figuie 1 . 



Fig. i. — Diagram of the ordinary mounting of a dynamo-electric machine 

 supplying a moiwphote light. 



(A) an inducted Gramme ring, or Siemens bobbin turn- 

 ing between the two poles of an inductor II', sustained 



