STATION-METERS.

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matter of uncertainty. The “ tell-tale ” will show him if any irregularities have occurred,and, if any, at what hour. It may also be known by this contrivance what man or set of menhave been negligent; for the retorts having their proper hours of work, will, if neglected,speak for themselves, and the men whose duty it is to look after them will be to blame.

The tell-tale is thus constructed:—In the centre of the dial-field a circular plate is fixed,connected to the train of indicating wheel-work, and made to revolve in a certain ratio tothe quantity of gas registered by the meter. Upon this plate a sheet of paper is secured,divided into twenty-four parts, which parts may be subdivided, Suppose the meter to register300,000 cubic feet in twenty-four hours, and the circular plate to be connected by wheels,in the ratio of three to one, to that index which marks a hundred thousand in one revolution,it is evident that the distance travelled by one of the twenty-four divisions of the plate fromacertain fixed point will.indicate the quantity of gas made in one hour, or — a ’ 4 -- = 12,500cubic feet. Above this divided disc is a timepiece, to the minute hand of which is attachedan arm, furnished with a pencil, which is made to press gently upon the disc by a lightspring. As the minute-hand of the timepiece revolves, the pencil bv means of a guide fixedto the meter-case, is so regulated, that in the first half-hour it would, if the paper were fixed,mark a vertical line in length equal to the diameter of the circle formed by the minute-hand,measured from the centre to the point on to which the arm is fixed, and in the second half-hour the line would be retraced by the hand rising again. This is supposing the divided discto be stationary ; but as it revolves in the manner previously described, the pencil will marka series of curved lines, meeting the divided circle of the disc every hour, and the distancetravelled from point to point will indicate the number of cubic feet of gas made during everyhour of the twenty-four. If the production of gas be regular, the figures formed by the pencilwill be regular also; if, on the contrary, any negligence have occurred, the irregularity of thefigure will detect it, and point out the hour and the amount of difference; because, if thespeed of the revolving disc be decreased, the figure formed will approach nearer to the straightline; if increased, the points of intersection upon the divided circle will be farther apart.

By reference to the diagram (Fig. 7S) the “ tell-tale ” will be understood.a is the divided paper disc upon which the curved line formed by the pencil is shown.b is the train of the wheel-work connected with the index markinsr 100,000.c is the timepiece and point at which the arm is attached to the minute-hand.d is the arm, to the lower extremity of which the pencil is attached.

Mr. Lowe used this instrument at the Chartered Gas Works in 1823, and it has since beenadopted very generally.

In the construction of the station-meter, less attention is paid to maintaining a regular andconstant flow of gas than is necessary in the consumers’ meter, in which it is important toavoid oscillation of the flame. Fig. 1 in Plate XXIII., though it serves well to illustrate thepassage of the gas through the measuring instrument, does not represent the form of drumgenerally adopted at present, for the projecting angular hoods offer unnecessary resistance toits motion through the water, and are therefore objectionable.

The following table shows the usual dimensions of the wheels of station-meters, for pass-ing the quantities of gas mentioned in the first column of the table, at the ordinary speedof one hundred revolutions per hour; that velocity being found most suitable for the action

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