16 Professor Tyndall [Jan. 17, 



currents. Using the magnets of the Alliance Company, by a skilful 

 disposition of his bobbins, M. de Meritens produces with eight 

 magnets a light equal to that produced by forty magnets in the 

 Alliance machines. While the space occupied is only one-fifth, the 

 cost is little more than one-fourth that of the latter. In the de 

 Meritens machine the commutator is abolished. The internal heat is 

 hardly sensible, and the absorption of power, in relation to the effects 

 produced, is small. With his larger machines M, de Meritens 

 maintains a considerable number of lights in the same circuit.* 



In relation to this subject inventors fall into two classes, the 

 contrivers of regulators and the constructors of machines. To the 

 mechanicians of the former class already mentioned may be added 

 Browning, Siemens, Carre, Gramme, Lontin, Achereau, &c. M. 

 Rapieff has hitherto belonged to the inventors of regulators, but I 

 have reason to know that he is engaged on a machine which when 

 complete will place him in the other class also. Instead of two 

 single carbon rods, M. Rapieff employs two pairs of rods, each pair 

 forming a V. The light is produced at the common junction of the 

 four carbons. The device for regulating the light is of the simplest 

 character. At the bottom of the stand which supports the carbons 

 are two small electro-magnets. One of them, when the current passes, 

 draws the carbons together, and in so doing throws itself out of 

 circuit, leaving the control of the light to the other. The carbons 

 are caused to approach each other by a descending weight which acts 

 in conjunction with the electro-magnet. Through the liberality of 

 the proprietors of the Times every facility has been given to M. 

 Rapieff to develop his invention at Printing House Square. The 

 illumination of the press-room, which I had the pleasure of witnessing, 

 under the guidance of M. Raj^ieff himself, is extremely effectual and 

 agreeable to the eye. There are, I believe, five lamps in the same 

 circuit, and the regulators are so devised that the extinction of any 

 lamp does not compromise the action of the others. 



Many other inventors might here be named, and fresh ones are 

 daily crowding in. Mr. Werdermann has been long known in con- 

 nection with this subject. Employing as negative carbon a disc, and 

 as positive carbon a rod, he has, I am assured, obtained very satisfactory 

 results. The small resistances brought into play by his minute arcs 

 enable Mr. Werdermann to introduce a number of lamps into a circuit 

 traversed by a current of only moderate electro-motive power. M. 

 Reynier is also the inventor of a very beautiful little lamp, in which 

 the point of a thin carbon rod, properly adjusted, is caused to touch 

 the circumference of a carbon wheel which rotates underneath the 

 point. The light is developed at the place of contact of rod and 



* The small machine transforms one-and-a-quarter horse-power into heat and 

 liirht, yielding about 1900 candles; the large machine transforms five horse- 

 power, yielding about 1)000 candles. 



