FIELD-BOOK.

The field-book is ruled into three columns: the centre contains all the dimensions of the chain from the station to the end of the line; the intermediate numbers are the points at which the offsets are taken at right angles to the chain, or at the crossing of fences, footpaths, &c.

The right and left columns contain the offsets that are taken on the respective sides of the chain; the margin on each side is for sketching the fences, buildings, and every necessary memorandum, such as the name of the field, the description whether arable or pasture (distinguished by the initial), the names of the adjoining proprietors or parish, &c., also the names of the occupiers. By carefully making these entries, it will be of great assistance in forming the reference.

Accurate and neat sketching will be of great assistance in plotting. Particular attention should be paid in showing the fences to which field they belong and where they change, at which point always take an offset; the ditch is always the boundary, and is noted in the field-book thus : the line denotes the ditch, the letter T shows the side on which the fence belongs; and of describing a fence in plotting when it changes, the same marks must be carefully attended to. Many expensive lawsuits have occurred through disputes in claiming the ditch boundary, particularly where much timber is growing.

OFFSETS.

When the ditch is next the chain, the offset is taken at right angles from the chain to the edge of the ditch, and when the ditch is outside, the offset is taken to the middle of the fence with the offset staff, and six or seven links added to it, as a general allowance for the ditch, about 4 feet 6 inches from the middle of the fence. In some districts the width of the ditch varies, therefore it is requisite at all times to inquire of the occupiers their local custom.

In measuring buildings, yards, &c., a tape is the most useful instrument for that purpose.

Sometimes there is what is termed a footset-hedge: that is, having no ditch either side; the offset must then be taken to the centre, and noted in the field-book thus .

A paling fence is known to belong where the nails are driven home, and described thus --, excepting when it is the boundary next a road; it has then sometimes a ditch outside. The usual allowance for a ditch must in that case be made.

Walls are distinguished by two parallel lines; footpaths and roads without fences by small dotted lines.

Buildings belonging to the estate or survey are usually tinted or hatched; and buildings not belonging have merely the outline.

The offset staff is also an important accompaniment to the chain; it is ten links long, painted white; each link is marked by a black painted ring, the bottom of the rod is shod with an iron spike, and the top has a stout open ring, as thus, to force or draw the chain through the bottom part of a fence. Offsets should, in general, be less than a chain. It is better to make a small triangle from the chain and have short offsets. See Line, Plate 11.

All stations or lines are numbered numerically, having a small circle round them, thus 1, as station or line one; and if two or more lines proceed from the same station, they are distinguished by a smaller figure over, thus (12) or (13), denoting that a second or third line commenced from that point or station.

Near to every fence a peg or mark should be fixed for an intended station or lines crossing it, and on other parts of a line where it is probable a line may cross it, and the number entered in the field-book; and against that number on the chain, in the offset column, a mark denoting that a line is intended to go from or through that line, and in the direction shown, as thus O, denotes a line at right angles or there

abouts on that side the line; or it may be two or three lines to the same point that will either commence or end at that point, as thus, showing the oblique or acute direction of the intended line or lines.

In measuring the principal lines of a survey, it is advisable to put down a peg at every ten chains, entering it in the fieldbook, as, in case of accident in dropping an arrow, it becomes doubtful which it was that had lost it; by going back to the last peg it is easily rectified. This precaution will be found useful in many other cases; particularly, when fields are very large, there would be no other marks left but these between the fences; and should a line be required to intersect or finish on it, the distance would be trifling to measure for the exact number on that line.

When a peg is put down for an intended station, that point may not be in the exact position by several links. The number originally entered in the field-book must not be erased; the pen must be drawn through it and the corrected number put underneath, and on the margin to show the working, that is, the number of links either added or subtracted from the original entry, as shown by Line 2, Plate 11. Reference to it hereafter removes all doubt of error, and explains the alteration; this will frequently occur in a large survey.

In all cases when a station is determined, cut a triangular hole round the station point, and fix the peg in the same hole in which the flag was fixed.

On any one of the lines nearest to the north and south, with a small mahogany box-compass lay alongside the line and take the magnetic bearing, so that a true compass bearing can be attached to the plan.

In taking angles for short lines, or for raising perpendiculars in cases of difficulty in crossing streams, or interruptions by buildings, &c., the box-sextant will be found to be of great assistance; for a description of which see Instruments, Part V.

In order to make an embellished plan of an estate, the surveyor cannot be too particular in noting every detail during his operations (particularly the course of hills, if any). He should also be well acquainted with ornamental writing, and have a knowledge of landscape drawing, to give the whole a picturesque effect.

SURVEYOR'S DUTIES.

There are a variety of duties belonging to a surveyor beyond that of measuring and mapping-viz.:

The assistance in the arbitration and settlement of disputed boundaries, manorial rights, the purchase and exchange of land for improvements, encroachments, diversion of roads, streams, &c.; a knowledge of timber falling, planting, and measuring; as well as a knowledge of mensuration of superfices and solids for measuring all kinds of materials and labour.

SURVEYING BY THE CHAIN ONLY.

Problem 1.

To ascertain the quantity of a piece of land without a plan. It is sometimes required to ascertain the quantity of a small plot of ground without a plan, but more particularly in agricultural purposes, to know the quantity of reaping, sowing, mowing, &c., in which case it is only measured as far as it is tilled, and all deductions made, such as footpaths, ponds, &c.

When the sides of a field are tolerably straight, it is possible to approach tolerably near the truth, but in inexperienced hands the quantities are frequently very far from it, particularly when a piece is measured by ordinates; that is, by measuring several widths across, adding them together, and dividing the product by the number of times, and that quotient multiplied by the whole length, taken up the middle, the product will be square links; this method is erroneous, and should never be adopted.

When a field is measured by ordinates (see Fig. 1, Plate 8), the length should be taken as near the middle as possible, and at the end of every chain put down a mark; at right angles to the centre line measure from one side to the other, as shown on plan.

Rule. Add the first and last length together as one sum; then take the 2nd, 4th, 6th, and 8th lengths, add them together, and multiply that sum by 4; then take the 3rd, 5th, and 6th lengths, add them together, and multiply the sum of them by 2; collect all three sums together, and multiply by the common distance, or 100 links, and one-third of the product will be the

area.

Another more simple method, without so much calculation : In measuring the line from A to B, put a mark at the centre or 50 of every chain; then measure from side to side through these points, add them together, multiply by the common distance, 100 links, or add two cyphers, the product will be the area in square links, which reduce to acres, roods, and perches, according to the rules before given.

This method is precisely on the same principle as the improved computation scale; as by that the fence at each end is equalised, and the length is taken in the middle of each chain, repeating that operation to the end without casting; so that it is similar to a piece of land perfectly straight, 3080 links long and 100 links wide, or 3.08000 =3A. OR. 14P.