158 ANNUAL OF SCIENTIFIC DISCOVERT. 



WILDE'S MAGNETO-ELECTRIC MACHINE. 



The principle is this : An armature wound round with insulated 

 wire is made to revolve rapidly in front of the poles of a larj^e 

 permanent magnet. The eurrents of eleetricity, thus induced in 

 the insulated wire, ai'C carried rounil a large electro-magnet, which 

 is thereby excited to a very iiigh degree. In front of tiiis electro- 

 magnet, a second covered armature is rotated ; and (lie electric 

 current thus generated is carried round a third electro-magnet. 

 It is from a rotating armature in front of this third magnet that 

 the electric current, ultimately used for heating or lighting ellects, 

 is produced. At each passage rouiul the electro-magnets, and 

 induction in the rotating armatures, the electric current becomes 

 magnitied to an extraordinary degree, until ultimately it is pow- 

 erful enough to melt iron bars in a minute or two, an<l to i)roduce 

 a light surpassing that of the sun itself. The machine is driven by 

 means of a steam engine, and, as almost the only current expense 

 is for motive power, it is not an improbable sujiposition that ere 

 long electric lights of the most intense description will be as 

 common in large factories and public buildings, as gas lights are 

 at the present time. 



The great, advantages of this over the old system of magneto- 

 electric machine ai)pears to l)e that it is capable of amplifu;aLion to 

 any required power, by a mere enlargement of the size of the dif- 

 ferent parts. His largest machine weighs about three tons. If, 

 instead of using the electric current generated by it to produce 

 dynamic elfects, we pass it round a still larger electro-magnet, 

 we should at once produce a vastly greater development of force. 

 The only limit which we see to this multiplication of power is the 

 excessive heat which would be developed in the rotating arma- 

 tures. One very interesting i)ractical ai)plication of this brilliant 

 and economical light is to photography, for which it is more con- 

 venient than the sun. By its aid more than two hundred nega- 

 tives can be exposed in a day, to secure gelatine reliefs. This is 

 the lirst practical application of the electric light to the commer- 

 cial working of photography, its constancy rendering it here more 

 valuable than an uncertain sunlight. — Quarterly Journal of Sci- 

 ence, 1866. 



ELECTRICITY AS A MOTIVE FORCE. 



Mr. !Moses G. Farmer, who has paid great attention to the ori- 

 gin and measm*e of electro-motive force, and the resistance which 

 the current encounters in its passage through metallic wires and 

 plates, has pointed out the numerical rules for computing the 

 mechanical power derivable from a given consumption of metal 

 in the battery, as compared with that furnished by an equal 

 weight of coal ; from which it aj^pears that, until some much 

 cheaper mode of generating electricity shall be discovered, this 

 force cannot compete, as a motor, on a large scale, with the force 

 derived from ordinary comljustion. 



