June 28, 1889.] 



SCIENCE. 



495 



mens type, but wound with a large number of turns of fine wire, 

 as the current passing through it is very small, in the arc machines 

 never exceeding .4 of an ampere. When the current passes through 

 the circuit, the armature revolves, and the machine becomes a 

 motor, of course setting up a counter electro-motive force, the 

 amount of which will depend upon the velocity of revolution of the 

 armature, and the strength of the field in which it revolves. The 

 speed of the armature is limited to a certain number of revolutions 

 per minute by means of a small belt running from the pulley on the 

 armature shaft to another one on the dynamo shaft, or on a line 

 shaft, or some other revolving shaft whose speed is constant. As 

 the speed of the armature cannot change, its counter electro-mo- 

 tive force can only change by reason of a change in the magnetic 

 strength of its field-magnets. The main current, on its way to the 



CLARK ELECTRIC COMPANY'S LAMPS. 



line, passes through the coils of the regulator field-magnets, and 

 thus supplies the field in which the regulator armature revolves. 

 If from any cause the main current should increase in strength, it 

 will at once cause an increase in the power of the field of the regu- 

 lator, and an increase in the counter electro-niOtive force of its 

 armature, which, being opposed to the e.\citing current of the 

 dynamo field, reduces that current at once, and with it the strength 

 of the magnetic field of the dynamo. This at once reduces the 

 generating power of the dynamo, and brings the current back once 

 more to its standard strength. If the strength of the main current 

 should decrease for any reason, the opposite action will take place, 

 the regulator field-magnet decreasing in strength, the counter 

 electro-motive force of its armature diminishing, and the current 

 through it and the field-magnets of the dynamo increasing, thus re- 

 storing the strength of the main current. There is another piece 

 of apparatus included in the regulator, and shown at the back of 



the cut. It consists of a solenoid, located in the main circuit, 

 whose armature is attached to a lever. The other end of this lever 

 carries a sliding contact piece, which slides over a number of sec- 

 tions or contacts of copper. A number of small spirals of german- 

 silver wire are connected to these contacts, and arranged so as to 

 form an adjustable shunt for the field-coil of the regulator, whose 

 resistance in the 30-light regulator is only .15 of an ohm. By means 

 of this arrangement, when the main current falls a trifle, the re- 

 sistance of the german-silver coils is diminished, and a greater por- 

 tion of the main current is shunted through them, instead of pass- 



CLARK ELECTRIC COMPANY'S AUTOMATIC REGULATOR. 



ing through the field-magnet coils. This, of course, causes a 

 further reduction of the magnetism of the regulator field-magnets, 

 the reverse action taking place when the current rises. It will be 

 seen by this description that the regulating power depends upon 

 the disturbance which is to be corrected ; and the greater the dis- 

 turbance, the greater is the regulating power ; and, as it is not 

 necessary that any thing should move, the regulating influence can 

 be exercised to a great extent instantaneously, while the entire 

 power of the regulator can be exerted in the fraction of a second 

 that is required for the lever of the solenoid armature to move. 



It is stated that the 30-light regulator exerts a counter electro- 

 motive force under extreme variations of the main current, rangino- 

 from three or four volts to seven hundred volts, which is enough to 

 control the dynamo under the most violent changes of load ; and, 

 as there is no train of gears nor ratchet movements to be put in 



CLARK ELECTRIC COMPANY'S AMMETER. 



motion, the regulation is accomplished in much less time than with 

 any other device in use. The simple form of ammeter shown is 

 supplied with each plant. 



The arc-lamps shown in the illustrations are storm-proof, and do 

 not require any hoods or other devices to protect them. The bind- 

 ing-posts are on the under side of the case, and will not become 

 short-circuited by sleet or snow. The switch is also on the under 

 side of the case, w-here it can be seen by the person operating it. 

 These lamps have been exposed to the worst storms of the past 

 winter; and, although at times completely covered with ice and 

 snow, they have never failed to start when the current was turned 

 on. The movement is claimed to be the most powerful ever put 

 into a lamp. The moving parts are heavy in proportion, the car- 

 bon-holding rod alone weighing sixteen ounces. 



