We put the world before you by means of the Bioscope and Urban films (Nov 1903)

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178 A Rheostat or resistance is necessary in order to reduce the current to the desired amperage. When the current is 100 or 200 volts, our special Kruppin wire resistance as Illustrated in this catalogue is most convenient, giving from 20 to 50 amperes by means of the adjustable sliding switch. When the voltage of the current is 200 volts, the resistance should he doubly as large in wire coils, and when purchasing a resistance, it should be distinctly mentioned whether it is for a 100 or 200 volt circuit. Many corporations have a 230 voltage, which is less favourable for reducing the current. A transformer or coil is recommended to be inserted in the circuit with the resistance. This answers the purpose of reducing the current from 230 volts to 70 or 100 volts, and thus making the current less unpleasant should a shuck be met with. The size of the resistance necessary would be practically the same whether for alternating or direct current. If it is alternating current, the carbons should be of equal diameter, and set in a vertical position. The most convenient size is about 16 or 18 millimeters. When the installation consists ol a direct current, two carbons should be employed of different diameter, and set at an angle of 30 degrees. The best size for the carbons in this case is 13 milimeters for the lower one and 16 millimeters for the upper. The reason why uneven carbons are employed is that the ncga.ive pole will consume the carbon quicker than the positive, and by using uneven carbons, this difference of consumption is equalized. For increased amperage proportionately larger sizes of carbon become essential. A wall switch or plug should be fixed up, containing a safety fuse in porcelain mountings as well as two terminals as shown by illustration. It is recommended that from this switch board flexible wire of best insulation should be used, of dimensions to carry 20 to 30 amperes with case. Before joining up to the switch board, (1) make your connections at the arc Limp setting both the carbons apart, (2) insert the necessary resistance in accordance witli the instructions given on the resistance, (3) join up the two wires to the switch board near the wall, (4) turn on the switch, (5) to create an arc light, turn the round milled head of the two carbon slides sharply to the left and back again to the right, by this means the carbons are brought into contact and separated again, thus creating the arc. The most convenient arc lamp is the hand feed One, as it obviates any complication or liability to get out of order. The construction is so simple that it suggests itself, and the regulating is performed by a mere turn of the screw at intervals, according to the distance of the carbons from another. Another advantage arising from the use of the hand feed lamp is that at the time of projecting a more powerful current can be used to get the best effect, and when not in use the current can be reduced. This cannot be done with an automatically fed arc lamp. The Urban arc lamp meets every requirement of the operator and is simplicity itself. Through its universal adjustment the light can be centred in a few seconds. After using the arc lamp the greatest care must be taken to switch off at the wall before disconnecting or removing any parts of the apparatus. Electric light is, however, still unobtainable in some places. The only substitute for electric light has up to the present been found in the oxy-hydrogen light. Oxygen mixed with hydrogen will yield the most powerful light next to the electric.