required for the several distances on the chain, whence the offsets are taken; and, secondly, that all offsets, are read either way, outward from the central column, in the same way as they are measured outwards from the chain.

To preserve uniformity, as it is more natural to measure from left to right, the place measured from, is put on the left of the central column, at the bottom of the line, and the station measured to, is put at the top, on the right; the points of commencement and termination of the line can thus be immediately seen.

The pages should also be numbered, for facility of reference, before beginning.

If the direction of the line is determined by an angle taken by the theodolite, or the bearing of the line be given by the circumferentor, the angle of the former or the bearing of the latter is placed in the central column, immediately above the starting point.

When the line crosses a road, or hedge, &c., make corresponding lines in the field book, as in Field No. 2, Plate 1, line 731 (page 48), at the distances 685, 695, and 731; which on reference to the plan will be easily understood.

In taking "offsets" to corners of fences, houses, &c., mark the relative position of the corner, as to the chain line (see 6.79 on line 6·90-page 47—and 0·10 on 7.31) in the example of "CHAIN SURVEYING," Field No. 2 (page 48), and generally be careful to make the field book, as much as possible, a fac-simile of the ground itself, with every post, hedge, house, &c., placed on the book, as to the central column, considered always as a line, in the same position as they stand to the chain on the ground.

Stations are generally expressed in the field book by the

following character ▲, which, in the plan, is represented by a circle in pencil, drawn round the station point, which should be always that of a needle.

In Chain Surveying, the BASE LINE, perhaps, had better, when referred to, be termed the base line AB, in contradistinction to the secondary lines, which are required in surveys of some extent, and are virtually base lines to their own portions of surveys, and may be lettered CD, EF, &c., &c.

But in all other cases, distinguish the lines by their lengths, and the points upon them, by the distance of those points from the zero end of the lines;-thus, in the example of the method of keeping the field book for chain surveying, Field 1, Plate 1, page 42, "from 574 on 635, to 34 on 485," the line begins at 574 on 635, and runs to 34 on 485—that is, the measured line is a line, connecting the point (574 on the line 635, measured from the beginning of the line) with the point (34 on the line 485).

And, again, at Field No. 2, page 47, "from 685 on 731 to 574 on 635," the point started from, is that point upon the line 731, which is 6 chains 85 links from the beginning of the line, and its termination, a point 574 on another line 635.

In theodolite surveying, it is better perhaps to use letters, as the stations are but few, and mostly come within the exceptions above referred to, being generally base lines to smaller portions of survey.

It is usual to take the bearing of the base line at the commencement of the survey, and enter it at once in the field book; the meridian line can then be put upon the

estate.

THE BOUNDARIES OF PROPERTY.

The brow of the ditch, or that edge of the ditch which is furthest from the hedge, is the usual boundary of the field. This, however, is not always the case.

The common allowance from the quick root, for the brow of the ditch, varies, in different places, being 5 links, 8, and sometimes as many as 10 links.

When a stream runs between two properties, the centre divides them. This is the case with a parish ditch, which is generally the water way from the hills.

CHAP. V.

SURVEY OF A FIELD OF THREE SIDES.

Let ABC be a triangular field to be surveyed-the first thing to be ascertained, is, whether a plan is required, or whether the area alone is sufficient.

If only the area, observe whether the sides AB and BC are sufficiently straight

and regular to war-
rant any point b to be
taken, from which
straight lines, drawn
to A and C, would
approximate suffici- A

B

ently with the area of the given triangle ABC. If they

are, arrange the field book in the following manner:

Having carefully selected the point b, it will only be requisite, in measuring along AC, to observe where a right angle from (b) would fall upon AC, note in the field book 250; leave a mark in the ground, and continue the measurement to C 5.60. Draw a line in your book, and measure from 2.50 to b=3·15; then (3·15)·(5·60)=8·82 square

chains area of triangle ABC.

If a plan be required, or the hedges AB and BC be so irregular as to require offsets being taken, it will be requisite, for the sake of the offsets alone, to measure round the whole field along the three sides. Let the field now assume the form in the accompanying diagram:

B

A.D

select any points A, B, C, commanding the longest and

nearest lines to the several hedges of the field, and place flags at those points A, B, and C.

First observe, whether the point A be exactly at the ditch ; if it is, put in the centre line 0, and in the right hand offset line 0; proceed till you come opposite 56 links, the first corner or bend D; take the offset (4) to D; this line, connected with A, gives the actual position of the ditch. Proceed along the line AC, marking down the several lengths as above, with their respective offsets, and selecting some point S, 5'70, to be noted as a station, whence to measure afterwards, a check to the point B; note it ▲ (a station) in the left hand column, as the check-line will be to the left. Having completed the measurement of the line,