When you meet with such obstructions, measure, with great care, an angle of 60°, either to the right or left of your direct line, and measure out, with the chain, any length so as to get clear of the object that obstructed your direct course, then take another angle of 60° with your present course, and measure the same distance as the last line. If this be done with great exactness and care, you will have arrived at the exact spot that your first direct course would have brought you to, had you met with no obstruction.

This process is simply measuring two sides and angles of an equilateral triangle, the third side being the distance, through the obstruction, from the last point arrived at to that from which you first diverted from your original course. Having arrived at this last point in your original course, measure the supplementary angle of 120° from the last measured side of the equilateral triangle, and it will direct you in the required course. In order to verify the measurement, the bearing of the line should be ascertained before and after having passed the obstruction, and if they were found to disagree, the work should be repeated.

To measure inaccessible distances with the chain and cross-staff only. When you meet with the obstruction, leave the chain stretched in the direction of your line, and measure, by means of the cross-staff, a line at right angles to the chain, so as to get clear of the obstruction; at the end of this line measure another line at right angles to itself, so as to clear the other side of the obstacle, and at right angles to this last line, measure a third of the same length as the first which deviated from the original course, and you will come on a point

in the original line; to proceed from which point in the proper course, you erect a perpendicular, by means of the cross-staff, to the last measured line; the length of the line, parallel to the original one, will give the distance across the obstruction.

Having measured the base line, construct triangles on it to the right and to the left, taking care to have them as nearly equilateral as the nature of the ground will admit. On the sides remote from the base line, construct other triangles, measuring the sides of each triangle, and noting them down in your fieldbook; and so proceed till the entire parish be triangulated. It is best to begin to fill in the triangles after having laid out two or three, lest the stations should be lost; but to guard against such an occurrence, great care should be taken to mark them well, by driving a short piece of wood, pointed at one end, fast in the station, and cutting a circle round it. It would also be advisable to make a note of some surrounding objects, as landmarks, by which the position or locality of the station may be easily discovered.

Before you begin to fill in your triangles, run proof lines from the vertex of every triangle, if possible, to close on the base; but should intervening obstacles render it difficult to run these proof lines from the vertex, measure them from side to side of the triangle, having them as long as the ground will admit. Having measured the sides of the triangles and proof lines, numerous tye lines are to be measured, from which offsets are to be taken to the several objects, ditches, fences, &c. in each triangle. With regard to the direction of these tye lines, circumstances alone can direct.

From these secondary lines, other tye lines might be measured if occasion required it. All these may be measured in any direction, without regard to the false stations erected during the measurement of the base or primary tye-lines; because having driven stakes at intervals of five or ten chains, the distance from any one of them to the point at which a line crosses "can be measured as correctly as if that spot had been fixed on for a station, when these principal lines" were measured. These primary and secondary tye lines will answer as good proofs of the accuracy of the chainage.

In measuring offsets, none should be longer than one chain.

If the boundary of the parish be very crooked, the extreme triangles must necessarily be small, so as to mark the extreme boundary by offsets not longer than one chain.

In measuring the sides of triangles, mark accurately where these lines meet with any hedge, ditch, river, lake, &c., and where any remarkable object is placed, omitting nothing that ought to be represented on the map of the parish.

It would be well to set marks at the intersections of all the hedges with the station lines, that you may know where to measure from, when you require to measure all the fields.

The place where you run upon or cross a chain line may be easily ascertained by setting up poles at two of the nearest stations on that line, the crossing will be at the point in a direct line with these poles. The persons at the poles will set you right, by directing you

to move to the right or left, according as the case may require, till you come to the required point, where it would be well to cut marks in the ground, pointing out the direction of the line. Such marks often save much time and trouble, as it may happen that the situation of some of your stations might escape your memory, which would at once be assisted by the direction of these marks which point out the direction in which they lie.

In a large survey, when two surveyors are employed, it is best to divide it into two parts by the diagonal or main line, which will answer both surveyors as a base line, one surveying the part of the parish or estate on one side of the line, while the second person confines himself to the part on the other side.

By this division the survey will be more expeditiously and correctly done, and the possibility of the lines of one survey becoming entangled with those of another avoided.

When four surveyors are employed on the same survey, run a base line, as in the last case, where only two were employed; then from some known point in this line run a cross line, dividing the entire into four parts, one of which is taken up by each surveyor. A separate admeasurement of the lines of separation which are common to every two, will serve as a check upon the chaining of those lines.

Particular care should be taken that you plot the work every evening, as in the event of an error in the measurement, you can easily discover and rectify it; whereas if several days' field work be allowed to accumulate, it might be a matter of great difficulty to discover in what particular line the error had been

committed. Hence the necessity of plotting the work as you proceed.

Having finished the plan of the entire parish, divide it into trapeziums and triangles, by drawing new pencil lines, and equalizing the boundary; and then calculate the contents of each figure by the rules already given for that purpose. The contents of the separate enclosures in the parish may be found by equalizing them in a similar manner. Some surveyors divide the plan into squares of 2 chains, by which each enclosure may be found. On this plan, it is usual to distinguish every fifth or tenth parallelogram by a thicker line. The number of squares will furnish data for finding the aggregate contents. The broken squares may be calculated by subdividing them into smaller squares. All the separate enclosures added together, ought to differ but little from the contents of the parish, as found without any reference to its subdivisions. A comparison of both contents will test the accuracy of the survey.

In closing these directions, it is unnecessary to remind the surveyor that the accuracy of his work depends on the accuracy of his chaining, plotting, and calculation. A little practice will soon point out the best modes of chaining in a direct line, which, with the apparatus usually employed by surveyors, is impossible. He shall soon discover that the plumb-line and vertical arch of some instrument to reduce sloping measurements to horizontal, are useful auxiliaries-that beam compasses, and scales with graduated edges, are preferable to any other for plotting-and that it will be advantageous to avail himself of fixed objects, such as steeples, obelisks, houses, &c. to chain to.