March 15, 1889.] 



SCIENCE. 



193 



The field-magnets (Fig. 4) are provided with an annular recess, 

 in which the annular armature (Figs. 2 and 3) rotates. It is claimed 

 that by employing this peculiar construction of the armature, and 



Fig. 4 — Field-Magnets, Sperry Dynamo. 



exposing its inner surface to the action of the inner pole-pieces, the 

 output of electrical energy is increased. 



Another feature of the Sperry armature is that there is no over- 

 lapping of coils, each coil being separate and distinct from the 



feJl^GATa 



others. Thus any mechanical injury sustained by one coil will not 

 cause the destruction of the whole armature, as the injured part 

 can easily be removed, and replaced by a new one, without dis- 

 turbing any other coil. 

 Each lamp is provided with a hand-switch, and also an auto- 



matic switch, which cuts the lamp out of circuit in the event of 

 neglect or carelessness on the part of the trimmer, or trouble in the 

 lamp itself. The regulation is such that the carbon rod is made to 

 operate in both directions, up and down, without friction. On 

 starting the machine, the normal arc is at once secured, and main- 

 tained throughout the entire operation. 



The discharge-plates of the lightning-arrester are movable, one 

 from the other, in such a way as to break the arc established between 

 these two plates, which follows the discharge of static electricity 

 from the line, be it produced by lightning or friction electricity by 

 belts, which has been discovered to be the case in some instances. 

 The arc being ruptured automatically, and the plates restored, no 



shutting-down of the light is necessary ; and the consumer knows 

 nothing of its operation, and is not annoyed by the extinguishing of 

 his light. All possibility of disabling the dynamo from lightning is 

 done away with, either from lightning direct or from the instanta- 

 neous short-circuiting of the dynamo, resulting from the arc estab- 

 lished between the two leads by way of the two discharge-plates, 

 which are present in all forms of lightning-arresters. These light- 

 ning-arresters have operated continuously for over two years upon 

 sixty and eighty light circuits. Heavy discharges have been taken off 

 of lines continuously all last summer and spring, and the apparatus 

 has not been injured in the least. A single lightning-arrester 

 serves for an entire circuit, being attached to both positive and 

 negative wires between the dynamo and first lamps on either lead, 

 the ground wire being attached to the rear terminal or binding-post, 

 all of which are shown in Fig. 5. 



