352 



SCIENCE. 



[Vol. XIII. No. 327 



nected, shunting the armature. Thfe automatic regulation thus 

 secured is practically perfect. Any number of lamps may be cut 

 in or out without visibly affecting the candle-power or brilliancy of 

 the lamps throughout the system. 



The terminals of the thin field-wires are not exposed to injuries, 

 as in so many systems, but are led in channels through the pole- 

 pieces to the field binding-posts. Both these posts and the main 

 binding-posts are mounted on a hard-wood board, which is secured 



without the least heating or sparking, — a fault so common in many 

 other systems. 



Although the dynamo is automatic in its action, a variation in 

 the speed of the engine or water-wheel might cause the lamps to 

 burn above or below candle-power. An instrument is therefore 

 needed to indicate at all times to the engineer or dynamo-tender 

 whether the lamps burn at normal candle-power, or, what is prac- 

 tically the same, at normal electrical pressure. The voltmeter 



FIG. 2. — NEW INCANDESCENT DYNAMO OF THE WESTERN ELECTRIC COMPANY. 



on the top of the pole-pieces. This board has an oblong slot 

 covered with wire gauze, allowing the warm air from the armature 

 to ascend, and at the same time preventing any thing from falling 

 on the armature. The armature is of the drum type, and is wound 

 in a very simple and peculiar way, avoiding all joints in the wires 

 but two. The commutator is very massive, and will last for many 

 years. From two to six sets of brushes, according to the size of 

 the dynamo,°carry the current from the commutator to the cables 



(Fig. 4) used for this purpose is simple in construction, dead beat, 

 and may be left in the circuit permanently without overheating. 

 It needs no recalibration, as it has no permanent magnets, and is 

 considered reliable. 



The rheostat or hand-regulator (Fig. 5), used to keep the elec- 

 trical pressure constant by increasing or decreasing the strength of 

 the field, is non-combustible. It consists of a cast-iron frame pro- 

 vided with porcelain insulators, to which german-silver wire coils 



