494 



SCIENCE. 



THE CLARK ELECTRIC COMPANY'S APPARATUS. 



The accompanying illustrations show the new apparatus of the 

 Clark Electric Company. The dynamo shows some points of in- 

 terest in details. It has an unusually long and deep commutator, 

 provided with two independent brushes on each side, either one of 



i the o 



[Vol. XIII. No. 334 



sented not.^ly to the outside of the armature, but to its inner sur- 

 face as well ; and by this means an enormous increase of the polar 

 surface is secured, which is claimed to render the wire cores more 

 effective than a sheet- iron core. The machines are shunt wound, 

 and are claimed to be the only high-tension arc-light machines so 

 constructed. They are calculated throughout to secure the highest 



CLARK ELECTRIC COMPANY'S IJYNAMO. 



which is able to carry the current, thus allowing the brushes to be 

 changed or turned over while the machine is in operation. The 

 shaft is very strong, being made of cast steel, and runs in gun- 

 metal bearings. The armature cores are made of cotton-insulated 



possible efficiency, and it is stated that after a long run no portion 

 of the machine is ever found uncomfortably warm to the hand. 



The principles on which the Clark automatic regulator works 

 will need a word of explanation. The dynamos made by the Clark 



iron wire wound into the proper form. A better division of the Company are shunt wound ; and instead of using an adjustable 



CLARK ELECTRIC COMPANY'S DYNAMO, SHOWING INTERIOR FIELD. 



iron is thus obtained than by making the cores of sheet-iron rings 

 with insulating material between them; but, as the core, in this 

 method of construction is laminated in both directions instead of 

 only in one, its magnetic resistance is somewhat increased, which 

 is a serious objection to such cores in most machines. In these 

 machines, however, the pole-pieces of the field-magnets are pre- 



rheostat in the field-magnet circuit, as is the usual practice with 

 machines of this class, the exciting current is varied by means of 

 an adjustable counter electro-motive force. This is accomplished 

 as follows : the armature of the small regulating-machine shown in 

 the cut is included, by means of its brushes and commutator, in the 

 field-magnet circuit of the dynamo. This armature is of the Sie- 



