[Electric engineering.] . illumination^ Machine shops , Thread and cloth mills Square Yards per 450-Watt Lamp. 2,000-2,500 1,400-1,600 600-800 200-250 200-230 26 ELECTRIC LIGHTING. 18 METHODS OF DISTRIBUTION. 29. We have considered the more important pointsrelating to the arc itself, and it is now in order to con-sider the lamp proper. The arc lamp must, besides beingarranged to hold the carbons in their proper position, beprovided with a mechanism to start the arc, or strikethe arc, as it is sometimes called, and also to feed the car-bons together as they burn away. But before looking intothe
[Electric engineering.] . illumination^ Machine shops , Thread and cloth mills Square Yards per 450-Watt Lamp. 2,000-2,500 1,400-1,600 600-800 200-250 200-230 26 ELECTRIC LIGHTING. 18 METHODS OF DISTRIBUTION. 29. We have considered the more important pointsrelating to the arc itself, and it is now in order to con-sider the lamp proper. The arc lamp must, besides beingarranged to hold the carbons in their proper position, beprovided with a mechanism to start the arc, or strikethe arc, as it is sometimes called, and also to feed the car-bons together as they burn away. But before looking intothe subject of arc-lamp mechanisms, it will be well to takeup the methods used for supplying current to the lamps,because this has a bearing on the style of mechanism used. SERIES DISTRIBUTION. 30. Most of the arc lamps used for street-lightingwork are connected in series. For example, in Fig. 17,A represents an arc-light dynamo in the station and /, /, /are arc lamps situated at different points on the street; DynamoF/ t, f represent the terminals of the lamps, and are marked -j-and — to distinguish them from each other. The currentflows through the lamps in the direction indicated by thearrows. The -|- terminal should in each case connect to § 18 ELECTRIC LIGHTING. 27 the upper carbon and the negative terminal to the lowercarbon. If one of the lamps B should be connected in thecircuit backwards, as shown, the current would enter at thelower carbon and the lamp would burn upside down; insuch a case the terminals should be changed so that the cur-rent will enter at the top carbon, as in the other lamps. Itis evident that in a simple series circuit the current throughall the lamps must be the same unless there is leakage toground and across to the other line, as indicated, forexample, by the dotted path a-b. There will be no leakageto amount to anything if the line is in proper condition, sothat it may be generally assumed that the current througheach lamp is the same. 31.
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