98 DYNAMO-ELECTRIC MACHINES. 



horse power, merely as an illustration, from a machine situated at 

 Meisbach, 36 miles distant, and which worked a small pump for sup- 

 plying water to a cascade in the exhibition building. This attracted 

 so much attention, that he was requested by the technical committee 

 of the exhibition, to make further trials with machines of a new 

 type, which he promised to do as soon as they were constructed. The 

 trials which are to follow are expected to be very interesting and will 

 be carried on with machines that will supply at least 12 H. P., and 

 will be transmitted, as in the first experiment, by ordinary telegraph 

 wires. 



The new dynamo-electric machine of M. Deprez presents this 

 special characteristic, that it is self-regulating under very wide limits, 

 working at a constant electro-motive force, no matter what the work 

 to be done may be, and preserving the same ratio between the power 

 absorbed and that utilized. His theory is that, whatever the dis- 

 tance, the duty performed by the machine will be the same. If this 

 is true, it would make very little difference to such a machine 

 whether the power to be transmitted was great or small or to a long or 

 short distance, provided the work to be done was within the limits of 

 the machine. 



The above principle is of very great interest in all application of 

 dynamos, no matter to what purpose it may be applied. When used 

 for giving light with arc-lamps, to enable one or more to be used at 

 pleasure, and to prevent accidents to the lamps themselves it is 

 usual to construct them with an independent equal resistance attached 

 and a self-regulating shunting arrangement, whereby the cur- 

 rent is automatically shunted through such resistance if anything 

 goes wrong. In addition to this, provision is made, where a number 

 of arc-lamps are used, say, in different parts of a building or pre- 

 mises, where it may be desirable to cut off a floor or any other por- 

 tion of a system by introducing resistances convenient to be got at, 

 corresponding to the number of lamps to be thrown out, so that the 

 electro-motive force of the machine may remain constant. This sys- 

 tem leads to a considerable waste of power, where the "number of 

 lamps fed by one machine is large, and any considerable portion of 

 them is thrown out of circuit. Because, if the machine is not feed- 

 ing lamps, the current is passing through a corresponding resistance, 

 and is consequently absorbing the same power from the motor 



