BOOK VIII.

TO SURVEY LARGE ESTATES,

TOWNS, &c.;

ALSO TO COLOUR AND EMBELLISH MAPS.

TO SET OUT AND MEASURE THE MAIN LINE OF AN ESTATE. Walk over the most elevated parts of the estate, from which you can have the most extensive prospect, accompanied with a person who is able to point out the boundaries of the estate; then cast your eye round the estate, by which means you will be enabled to ascertain the proper situation of your main line. Fix a pole, and let your assistant fix another about six chains distance; then look both ways along the intended line, and move one or both of the poles until you are clear of all obstructions, such as woods, hills, &c., and in a line with two distant objects; but let your objects be as distant as possible, if without the estate the better, as these objects will serve to check your line as it is set out, and also assist you in finding the line in future, if the poles are taken up. When the line is thus ranged begin at one end and measure it. Be particularly careful in noting down the fences which you cross, also in leaving stations, and taking offsets to such fences as are near.

Every estate was anciently a large tract of land or a common, and as land increased in value was divided and subdivided by fences into fields or closes, and any number are denominated an estate. In order to obtain a correct idea of

the figure thereof, walk round the estate or through such parts, so that you can see the principal part thereof, and carefully inspect the form of the boundaries, principal roads, drains, &c., which intersect or divide the estate; and also remark the proper situation of the principal lines, and in what figures the whole should be divided into. After you have got a pretty good idea of the estate, measure it as a single field, according to the rules laid down in book VII. After you have divided the principal part thereof into one or two large triangles, &c., divide each part into three or four parts, according to the size, by lines which run from line to line, or from station to station, along some of the principal roads, fences, &c., or where it may be deemed most necessary; and each part is also subdivided in a similar manner, till every fence is obtained by a measured line.

GENERAL DIRECTIONS IN SURVEYING ANT LARGE ESTATE.

1. Never measure your principal lines from short ones, but let every principal line be measured from the main line. Surveying is similar to building a house, the foundation is first laid and the whole built thereon, so every line is constructed on the main line, without which it is impossible to measure with correctness.

2. When two surveyors are engaged in one survey, a base Ene is measured and each surveyor works on each side of this Ene. At the commencement, one surveyor ranges this Ene and the other measures it.

8. Some surveyors have three assistants, two to the chain, and the third so range out the lines, make stations, &c.; and this is a very good method in a large suver,

4 The general rule adopted by surreras is to measure every internal Exe from a fixed point in one line to another Exed point, or from station to station, so that every line may

prove itself, and also the figure in which it is drawn. This method, for simplicity, accuracy, and expedition, has not its equal.

5. Measure every base line as long as possible, and between two extreme angles of the estate; woods, hills, &c., sometimes will not admit of this method, in this case you must measure it as well as circumstances will permit.

6. If you can procure a plan or sketch of the land you are surveying, it will greatly assist you in forming your lines, &c. Also when you return to and from your survey, note down in your field-book how the principal fences run, and form lines in your imagination.

Measure your lines in the same order as you intend to lay them down on the plan; the three first lines should form a triangle, then the principal division lines, and lastly the lines in each division; and never measure a part of one triangle, and then a part of another, as a learner will find much difficulty when he commences to draw the plan: the best method is always the most simple and most easily learned.

8. The best surveyors are particularly careful in selecting the situation of their main lines; it is not their object to range every line to measure a fence, but that it may be clear of trees, woods, quarries, rivers, &c.; as the accuracy of the whole survey materially depends on these lines. If exactly measured and correctly laid down on the plan, the short lines will generally agree, and if not, a mistake is readily discovered, but not so readily in a constructing line.

9. Some surveyors measure all the principal lines, dividing the survey into large triangles, before they complete any one part; others cut off a large triangle, and complete it before they begin another triangle, &c.; the latter method is preferable to a learner, as the lines, stations, &c., are more recent, and therefore better impressed on the memory.

THE ORDER IN WHICH ANY ESTATE SHOULD BE SURVEYED.

I. Base Line.-Let this line be as long as possible and clear of all obstructions, and between two extreme corners of the estate.

II. Figures.-After you have measured your base line, divide the estate into triangles, if broad; but if the contrary, into triangles and trapeziums upon your base line; but let one triangle be at each end of the base line, as this will, enable you to begin the plot at that end which is most convenient.

III. Division Lines.-These lines should be measured from line to line, if very long; but if short, from station to station. These lines, if properly run in opposite directions, will remove every difficulty; and if a mistake is committed, it may readily be discovered when these lines are laid down on the plan. The pupil is particularly requested not to be too sparing in taking such lines, whether they take fences or not, as this method surpasses all others both for expedition, simplicity, and accuracy, whether practised by a learner or a practitioner. See line 25-14, plate XI.

IV. Subdivision Lines.-After each triangle or trapezium is divided by the division lines into separate parts, measure the subdivision fences by lines which run from station to station, till all the crooked or curved fences are obtained by a measured line, but the crossings at or near the ends of straight fences are sufficient when there is no intermediate fence. See a-b, fig. 1, plate VIII.; and the same order should be observed in plotting as in measuring an estate.

1. The base line is laid down.

2. The principal figures are constructed thereon.

3. All the division lines are drawn between their respective points or stations.