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Page:Popular Science Monthly Volume 57.djvu/196

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186
POPULAR SCIENCE MONTHLY.

Concerning this apparatus many erroneous notions prevail. One of these is that a householder may burn thousands of feet of gas without cost to himself, provided he keeps the company in blissful ignorance of the employment of gas for heating purposes upon his premises. The demonstration of the falsity of this idea lies within the reach of any one who will take the trouble to read his own meter on those days on which the company's indexer pays his monthly visits.

Figs. 1, 2 and 3 represent different states of the index usually employed on the three, five and ten light meters, the sizes commonly found in our dwellings. The smaller dial, placed centrally above the other, is known as the 'proving dial,' and, being used merely for testing purposes, is not considered in reading the gas consumption. Although the index dials vary in nomenclature as well as in number, it is generally safe to consider that if the name is placed above the

PSM V57 D196 Different gas meter reading 1.png
Fig. 1.—Reads 3,300 Cubic Feet. Fig. 2.—Reads 19,800 Cubic Feet. The apparent reading is 29,800. The gearing of the indexing mechanism is not especially delicate, and it frequently happens that the dial of one denomination begins to record before the hand of the next lower denomination has made a complete revolution.
PSM V57 D196 Different gas meter reading 2.png
Fig. 3.—Reads 19,800 Cubic Feet.

dial a complete revolution of the pointer is required to register the amount of gas indicated by the name; whereas if the name is placed below the dial each numbered division of the dial represents the amount corresponding to the name. If doubt still exists as to the value of each division of the lowest or right-hand dial, remember that no meter index is designed to read less than one hundred cubic feet for each division of the circle.

After one has indexed his own meter for a month or two he is in a position to begin checking the bills presented. The 'present state of meter' and the 'previous state of meter' are always specified, and the mere subtraction of the former from the latter gives the consumption. This is not invariably the case, however. After a meter has registered its maximum reading—100,000 in the smaller sizes—it passes over the zero point and begins to build up a new record. This happens at