DYNAMO-ELECTRIC MACHINE. 97 



machine. Niaudet, a French writer who seems to have treated the 

 subject exhaustively, is of the opinion that Brush's machine is faulty 

 in construction and that the ring used is very old, being the one used 

 by Paccinotti, who was the first to construct a machine of a type from 

 which the Gramme has descended. Brush has made some changes 

 in the details of his machine, but they are not considered to be of 

 much advantage. Although there are some faults of a serious nature 

 in the Brush, he is credited with being the first to solve the problem 

 of lighting a number of arc lamps in series, with one machine, with 

 but one conductor leading front it. He has built machines, as already 

 stated, capable of supplying 60 lamps, which have probably the high- 

 est electro-motive force in existence, although it is claimed that a 

 machine made in Germany, a modification of the Gramme, has a 

 higher still. The 40 light machine must have an electro motive force 

 of 2000 volts, which is sufficiently high to kill a regiment instan- 

 taneously, if they were joined hand to hand with their hands moistened 

 with acidulated water, and the first and last man were connected to 

 such a machine 



The type of machine made by Gramme, with eight magnets 

 arranged in four pairs and four sets of brush collectors, already 

 referred to, has a very high electro-motive force and was designed 

 by him for the transmiseion of power to a distance. The arrange- 

 ment adopted in this machine enables it to be used either in quan- 

 tity or tension. The ring being wound double, as it were, and hav- 

 ing two commutators, with two pairs of brushes to each, gives rise 

 to four separate and distinct currents, which may be utilized in var- 

 ous ways as may be desirable. One set of collectors are usually em- 

 ployed to furnish -the current for the electro-magnets, which may be 

 afterwards added to the other three in quantity. The four currents 

 may thus be joined together, and used as a current of quantity, or 

 may be joined two and two, or may be all united in series, having an 

 intensity of one, with the electro motive force of the four. This last 

 arrangement would enable the machine to transmit power to a great 

 distance. The problem of the transmission of power to a distance is 

 occupying the attention of Frenchmen very much at present. At the 

 recent electrical exhibition at Munich, M. Deprez, who is the inven- 

 tor of an absolute galvanometer, which will be described further on, 

 was enabled by a machine of special construction to transmit a half- 



