Left off- C FIELD-BOOK. Main lines. Right off sets. AC, S. 60° 25' E. 1896. 844 Including offset to cor. 86 746 Close to A. 152 688 594 462 200 Ꭰ he main lines AB, BC, c.; and the other two re for the offsets, accordng as they are on the right r left of the main line. or this purpose it is best O begin at the bottom of he field-book, and to write pwards, that the offsets n the right side of the main line may be placed the right-hand column, nd the offsets on the left de in the left-hand coumn. Thus, in measuring rom A to B, the offset Aa, which measures 106 Inks, is on the left hand f AB, at the beginning f the line; therefore write in the middle column, t the bottom, and opposite o it, in the left-hand coumn, write 106. Then measuring along AB, the point f is to be found, upon which the perpendicular alls from F: this is 284 inks from A, and ƒF is 200 links; therefore write 284 in the middle column, and 200 opposite to it in the left-hand column. Again, at 442 links from A, the line AB crosses the boundary-line FG; therefore write 442 in the middle column, and in the adjacent columns draw straight lines in the direction of the straight line FG nearly, for the exact position of it is not required at this stage of the survey. At 530 the perpendicular from G meets AB, and Gg is 108; place therefore 530 in the middle column, and 108 opposite to it in the right-hand column. B To left. Proceed in this way to B, where, besides the offset, BI is measured, and placed in the left-hand column, with the mark to show that it is not perpendicular. At the same place in the right-hand column is placed the mark F, to show that now the surveyor turns to the right hand. This finishes the survey along the line AB, and a line is drawn across the book to separate it from the next line. Proceed in the same way from B to C, from C to D, and from D to A. The position of any one of the lines, as AC, being found with the compass, it will determine the position of the whole. But in using the compass, the variation should be allowed ; and great care ought to be taken lest the needle be attracted by some metallic substance in its neighbourhood. Ans. Area 14 acres 2 roods 19 perches 22 yards 17 yds. 5.558 feet. Lay down the plans of the following properties from the field-book for the three examples, and calculate their contents. C Fig. 1. Fig. 2. A B PROB. XXVIII. To take an extensive survey. Choose for stations the most eminent places, from which the principal parts of the survey may be seen. Particularly choose uch eminences as lie near the boundaries. Take the angles which these stations make with one another with great accuacy, and measure carefully in a straight line the distances rom station to station, marking the places where the lines Dass ditches, roads, rivulets, &c., and take offsets to near bjects, leaving in the ground a mark at every place where you marked the distance in the field-book, distinguishing these marks by letters or figures, that they may not be mistaken for one another. In this way you will obtain the situation of the principal parts. Then take other stations within these, and measure the distances as before. And thus divide and subdivide the survey, till you come to single fields, which may be measured by some of the preceding methods. The longer the distance is between the stations, if accurately measured, the more correct will the work be; but this cannot be ascertained by a single measurement, without using various methods of determining it. At the same time, an error in these primary distances affects the whole survey; and therefore every care ought to be taken to prevent it. After the principal parts of the survey are laid down accurately, so as to have the whole divided into small compartments, these may be filled up by the plane-table, one by one. In laying down the plan, proceed in the same way, first laying down the principal distances and the boundaries, and then the interior parts as they are surveyed; and in filling up the particular departments, care must be taken to lay down the boundaries of parishes, estates, farms, &c. and to point out the particular situations of towns, villages, churches, gentlemen's seats, towers, farm-steads, also rivers, lakes, ponds, woods, plantations, rocks, precipices, and all the eminences, mines, pits, quarries, and in general every thing which can contribute to give a proper understanding of the nature of the survey. All these must be neatly sketched and properly coloured, and the names of the places are to be printed in them. 1. I took two stations near a road, of which B lay from A, N. 61° E. 1850 links; and from A took the bearings of the eminences C, S. 70° E., D, S. 62° E., and E, S. 36° E., and at B took their bearings C, S. 14° E., D, S. 61° W., and E, S. 26° W. Required their distances from the stations, and their bearings and distances from one another. Ans. BC 1684 14, AE 1201.788, CD 596-64, and D 753.41 links. S |