To Survey with the Chain only. The Parish Survey of England, under the Tithe Commissioners, is in general executed with the chain, which, when used with care and judgment, gives in surveys of moderate size, results sufficiently accurate; but that it should supercede the use of the theodolite, in such an extensive survey as that above alluded to, it is not easy to conjecture. When we use only the chain, we are always limited to one figure, namely, a triangle, the sides of which should be measured with great accuracy, a task extremely difficult, when the ground to be chained is hilly, or covered with clumps, bushes, or other obstacles; such as high walls, thick hedges, deep ditches, &c. A small error in the length of even one of the sides of the triangle will affect the correctness of every part of the survey depending on that side, and also the relative position of the ground when delineated on paper. Hence the necessity of using extreme caution in the admeasurement of the sides. In measuring lines on slopes, a certain number of links must be deducted from each chain, so as to reduce them to the horizontal measurement, otherwise the survey cannot be plotted, and the result will show a greater quantity of land than there really is. For this purpose the theodolite is generally employed. * The theodolite, with the method of levelling and adjusting it, shall be fully described further on. end D of the slope to be measured, then directing the telescope towards the object, elevate it till the cross wire intersect B, then on one side of the vertical arc will be the angle of elevation of the slope CD, and on the other the number of links to be deducted from each chain of the slope CD, in order to reduce it to the horizontal measurement CE. As an example, let us suppose the angle of elevation to be 16°, then on the other side of the arc will be found the figure 4, which signifies that 4 links are to be deducted from each chain contained in the line CD, to find the horizontal distance CE. Where it is required to take many offsets, or cross several fences, it will be of advantage to make the necessary allowance in the field, noting only the horizontal distance in the field book; but where great accuracy is required, it is best to note the angle of elevation and length of the slope, and make the necessary allowance from the following table, when plotting the work. By referring to the following table for reducing hypothenusal lines to horizontal, it will appear that a reduction of only 3.874 links ought to be made when by the theodolite you make a reduction of 4 links, shewing that where extreme accuracy is required, recourse must be had to the tables. Reduction in Links and Decimals, upon each Chain's length, for the following Vertical Angles. Angles. Reduction. Angles. Reduction. Angles. Reduction. When properties are separated by hedge and ditch, it is necessary to ascertain from one acquainted with the usage of the country, which is the boundary; as in some places the brow of the ditch is the boundary, while in others the roots of the quicks, or the foot of the bank, forms the line of separation. In crossing a ditch or very abrupt precipice, the chain should be kept in a horizontal position, and the end marked by a plumb suspended therefrom. The follower should always hold his arrow close within the handle or loop at his end of the chain, while the leader holds his, and sticks it in the ground close outside his end. In practice, it is frequently required to chain a line, the extremities of which cannot be seen by two persons stationed there, by reason of high ground intervening; in this case two long poles, furnished at top with flags, should be stuck in the ground at A and B; and two persons with A } B CD very slender poles should put themselves in a direct line with those, by placing themselves in some intermediate position, and moving from side to side, till one placed at C cover A from the person standing at D; at the same time the pole at D covering that at B from the second standing at C. Then having two fixed objects C and D, in the right line to be measured, which are visible from either extremity, the chainsmen may proceed towards these intermediate poles. A little practice will always suggest to an intelligent surveyor, the most judicious plan to be employed in every difficulty which may present itself. To measure Offsets. Let A, c, o, d, e, f, g be a hedge, brook, or ditch. ath chain to c, at right angles to AB. In the field book write the length of Ah (137), and ch (50), as in the margin. Next note the distance and offset Ai, io, and so proceed till all is done, placing the distances measured on AB to the right of the vertical line, and the offsets to the left. But should it be required to take offsets to either side of the line AB, then the several distances along this line should be written between two parallel vertical lines, and the offsets to the right or left, B 56560 53 470 48 370 36 145 50 137 A opposite each respective distance, according as the point to be measured to lies to the right or left of the line AB, making a sketch of the hedge, brook, &c. as you go along. To plot the work from the field book, mark off the several distances Ah, Ai, Aj, &c. along the graduated edge of the scale, and the offsets hc, io, jd, &c. on an offset scale; then connect the points A, c, o, d, &c. To Survey a single Field with the Chain only. Having observed before that in a chain survey we are limited to a triangle, it may be necessary to observe, that in laying out the triangles in the field, care should be taken that each be as nearly equilateral as the nature of the ground will permit, avoiding as much as possible angles which are too acute or too obtuse. Let it be required to survey the five-sided field A, B, C, D, E. Placing a conspicuous mark at the corner of the field from which you start, as at A, |