Measuring cards, two separate cards having formula and procedure for measuring the Radius of the Curve of a rail line.
(1). Light khaki paper on light timber with handwritten formulae and instructions on it in brown.
(2). Light khaki paper on both sides of card with handwritten formulae and instructions on it in black.
Hand written rectangular cards with a diagram indicating the procedure and a scale of the radius (in chains) for different offsets of the 20ft chord to the curve of the rail. The offset is the difference in feet between the centre of the string indicating the chord and the centre of the rail curve marked by that chord. Thus (as can be seen on the top scan) for an offset of 2 1/8th inches the radius of the circle of which the rail curve is an arc is 4.28 chains (a chain is 22 yards or 20.1168m)