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CHAPTER IX.

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Quantities of Materials (Cont'd.)

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IV. Special Methods of Measurement of Quantities.

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1. Volumes of Brickwork.

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Method of Measurement.

To illustrate the use of the table in this
connection, let us suppose Fig. 6 of Plate V
to be the cross-section of a tunnel to be lined with brick in the manner
shown, the irregularities of the tunnel to be filled in with brickwork,
and that we desire to know the number of brick used per linear foot, the
drawing
being made to a scale of ¼ inch to 1 foot.
Looking in Table 10 we find the setting for
the given scale to be 285.6 and the value of the Relative Vernier Unit
to be 4.0.

Adjusting the Planimeter to the given setting, and having brought the
instrument to a Zero reading the area of the cross-section of the brick
lining is traced in the usual manner. Let us suppose
the reading of the instrument for this tracing to be say 9256 Vernier Units.
Then since the value of the Vernier Unit for this scale is 4.0 we have

9256 × 4 = 37024
which is the number of brick per linear foot required.
It is evident that since the Planimeter gives the number of brick per
linear foot for the area traced, the quantities of brick in house walls
and similar forms of construction is at once obtained in exactly the same
manner by simply tracing the elevation of the wall directly on the plan
of the building and multiplying the result by the required correction for
any given thickness of wall other than 1 foot. The openings for door or
windows can be traced but ordinarily this is not done in the measurement
of house walls, the walls being usually counted as solid to allow for the
extra work involved in the construction of such openings.

If, as is often the case and especially in retaining walls or foundations
the result is required in Cu. Ft. or in Cu. Yds. instead of number of brick,
Table
3 or Table 3¹ would be used respectively in place of Table
10— the operation however being exactly the same in each case whichever
Table were employed.

In the preparation of the Table the average
number of brick per Cu. Ft. was taken as 18.5 brick which will be found
to be a very close approximation, and any result obtained by the use of
Table
10 can be at once reduced to Cu. Ft. or Cu. Yds. by simple multiplication.

The method of finding the factors given in this Table
is easily seen from the general Equations and mathematical
discussions given in Chapter III and need not be repeated here. The
Table
is intended to cover every possible case in the measurement of brickwork
and factors are given for every scale to which plans for brickwork are
usually drawn.