in its lowest position, this pin can be brought under the yoke of the bar 1, so that the handle remains down, i.e. the pencil remains on the paper. The releasing cord is carried from the reel 1 round the fixing screw at the back arm of the releasing lever between the two discs at the clamping screw 2, round the nut 3, over the pulleys 4 and 5, in the direction of the arrow. Thence it is carried over the pulley 1 (Fig. 77) at hinge A, then over the pulley 1' at hinge B. Care is to be taken that the cord is carried over these two pulleys in the same direction otherwise the cord will become lengthened or shortened by the movement of the instrument during work. From the hinge B the cord is carried to the pulley on the pencil sleeve (P, Fig. 77) and fastened to the clamping arm under the sleeve of the pencil point. By winding or unwinding the reel 1 the cord is given such a length that, when the handle G is raised, the pencil point is also raised as much as possible, and, when the handle G is lowered, the pencil point rests on the paper and the cord is slack. This length of cord is maintained by tightening the clamping screw 2 on the tracer bar yoke. The instrument is now ready for

use.

(b) Setting with Pole at the end (Figs. 75 and 80)

If the pantograph is to be used for ratios under, it is advisable to set it up with the pole at the end. (See Fig. 75.) For this purpose the frame is placed at the end of the table and the axis Pk' is made

K k

37

FIG. 80.

vertical by means of the screws S, S and the box level. The pole-ball pin is taken out of the sleeve Z on bar 2, placed in the sleeve at the hinge P, secured with the nut, placed in the bearing at the foot P, and the bolt drawn over it. The longest wire is attached to the supporting tube and to the top eyelet of the frame at k': the shortest wire is attached at h to the bar 3 and to the frame at k', the bars 3 and 4 are adjusted horizontally by means of the eyelet screws h

and h' on the supporting tube and bar 1 by means of the screw on the caster r', whereby bar 2 is also brought into a horizontal position. For pantographs of more than 60 cm. length of bar the frame must be loaded with additional weights, in order to obtain an absolutely steady position of the axis Pk on the table. With instruments of 72 cm. length one such weight is supplied, with those of 84 cm. and 96 cm. length two, which are pushed from the back over the curved stand K and placed one on top of the other. After these weights are applied, the vertical position of Pk, and the horizontal position of the bars 3 and 4 must again be examined and, if necessary, adjusted. The pencil point is now placed in the sleeve Z on bar 2 and connected with the releasing mechanism by fastening the clamping lever of the releasing cord to the bottom of the pencil holder and leading the cord over the pulley on the pencil point sleeve, over the pulley 1 at hinge A, and thence to the releasing lever in the same way as described under (a).

For enlarging with this setting of the instrument (Fig. 75) the

tracer is placed in the sleeve Z on bar 2 and the original drawing also placed there. The pencil point is placed in the sleeve F on bar 1, underneath which the clamping arm of the releasing cord is fastened to the pencil point. From here the cord is now led over the pulley 5 on the tracer bar (Fig. 79) over the pulley at hinge A and thence, as when reducing, back again over the pulley 5 to the releasing lever. In the case of big enlargements it is advisable only to set the angles of the rectilinear figures as exactly as possible, to reproduce them on the enlargement and then join them up with lines. In the case of curved figures, points are also marked at suitable distances and joined up by freehand on the enlargement. When using the pantograph for this purpose, i.e. for enlarging by pricking, it is advisable to leave the tracer in the sleeve F and use it as a pricking point by removing its prop and screwing down the nut with the spring sleeve till the tracer point is 3-4 mm. clear of the paper: the prop c (Fig. 79) is now brought to the pricking point in the sleeve Z which is used as the tracer, after removing the protecting

sleeve. The moving of the instrument is also effected with the handle G.

(c) Frame with Suspended Foot.

L

When making large reductions & to, the foot P of the frame, or the whole of the latter rests entirely on the paper on which the reduction is drawn, so that it is somewhat difficult to get the parallel sides of the original and of the reduction to coincide. The new frame has therefore been made with a suspended foot. This foot stands about 5 mm. above the surface of the table and reaches 40 cm. over the table, from the edge, so that the drawing paper can be easily pushed under the foot, until the pencil point stands at the same angles of the reduction to which the tracer is set on the original.

FIG. 82.

The above illustration (Fig. 81) shows the application of this new frame and its connection to the pantograph. The head, with the four set screws S (Fig. 82), is put in the case separately. For connecting same with the frame the ends of the four screws are placed in the grooves in the top of the frame, the connecting pin, fixed thereto by a cord, is pushed through, and the screw S slightly tightened. In order to make the axis o o (corresponding to Pk in Fig. 80) vertical, a box level with connecting rod accompanies the instrument, the application of which can be seen distinctly from Fig. 82; the box level is set by means of the four screws S and the correct position of the same is examined and corrected in the same way as indicated under (a) for the axis Pk. When using this new frame for the setting with pole in the centre, the areas which can be traced are smaller than in the case of the ordinary frame. This new frame is only supplied to special order.

H

CHAPTER V

THE SUBDIVISION OF AREAS

BEFORE engaging in the work of measuring distances in the field, for the purpose of subdividing areas, setting out allotments or building plots, a survey of the land should be made, or a tracing of the area to be divided taken from the Ordnance Map. On this plan or tracing the subdivision should first be carefully set out, and the actual measurements in the field made from it.

When measuring along a straight line to stake out new fences, the measurement should always be a continuous one, as it will be found that a mistake can easily be made if each piece or frontage be measured separately. As has been carefully pointed out in Chapter II these measurements must be horizontal.

It will serve as a check if the line measured closes on a station in the survey. Fig. 83 shows a tracing of the plots set out in the office for use in the field.

AB is 12 chains long from station A on the survey to station B. The lengths of each added together are, of course, equal to 12 chains, and the areas of each plot added together are equal to the area of the whole rectangle ABCD. If the rectangular plot of land ABCD be for sale in plots, and it be required to measure off plot No. 1 which has been sold, the remainder should afterwards be measured, and the two areas should together equal the whole area ABCD.

These

The stakes used for marking out allotments or plots of land should be, say, 2 inches square and 15 inches long. should be put in nearly level with the ground. If nails be

driven into the stakes at the top, so that they project perpendicularly say half an inch, and a cord be stretched from nail to nail, the ground, if pasture, may be nicked out along this line to indicate the exact position of the new fence.

When dividing lands for purposes of sale or otherwise, it is always advisable, when the division is to be made between arable and pasture, to see that the ditch is in the arable field.

Building plots should be measured in feet and inches, and the frontage and depth figured on the plan.

The measurement of land under crops and woods should not include hedges or ditches, when it is made for the purpose of payment of labour.

When an agent has the management of a home farm, he should make a plan showing the exact positions of all permanent objects such as trees, gate-posts, &c. By this means he will be enabled

to ascertain quickly the areas under the different crops by measuring along the fences from such fixed points. The cropping may then be shown on the plan after computation in the office by aid of the scale.

The Ordnance Map may be used for making this plan by taking a tracing of it on good tracing cloth.

To lay off a plot of land of a given size, from a rectangular fleld. If we divide the area required to be set off by the length it gives us the breadth, and vice versa.

Example.-Let ABCD (Fig. 84) be the given field: it is required to lay off a plot of land equal to 3 acres. The side AD is 6 chains. Divide the area (3 acres) by this side and we get the length of the sides to be measured off along AB and DC.

A line joining the points E and F will give the required area,

viz. 3 acres.