DYNAMO-ELECTRIC MACHINES. 



77 



M . ( Jrammo has devised an apparatus called the cut-out (Fig.13), 

 which automatically cuts the circuit open when the main 

 current becomes weakened to too great an extent by the inverse 

 current. The working of this apparatus, which is based on the 

 antagonistic actions of an electro-magnet and a spring, is too 

 simple to require any description, and can be easily understood 

 by a mere reference to the illustration. 



TABLE OF GRAMME MACHINES FOR ELECTROPLATING (CURRENT TYPES). 



SIEMENS MACHINE. Tlie very rapid commercial develop- 

 ment of the Gramme machine has given rise to a large number 

 of similar machines, which are presented sometimes with a 

 certain difference in the bobbins, sometimes with some new 

 shapes of frames or of electro-magnets, and even sometimes 

 with no other alterations than those resulting from a change in 

 the sizes of the parts. 



The most important of these machines is, without doubt, 

 that invented by Mr. Hefner von Alteneck, and which is 

 generally known under the name of the Siemens machine. 

 Its success, which nearly equals that of the Gramme machine, 

 is derived from its intrinsic merits, the care with which it is 

 manufactured, and the really colossal industrial power of its 

 godfathers, Messrs. Werner Siemens at Berlin, and the late 

 Sir William Siemens, of London. 



The Siemens machine, which we illustrate (Fig. 14), prin- 

 cipally consists of a central cylindrical bobbin and two electro- 

 magnets composed of a series of bars of soft iron, bent in the 

 middle so as to as nearly as possible surround the bobbin. 



