chain in his right hand at the first mark, or beginning of the line. Then, if the leader is in a direct line with the mark, he must put down the arrow which he holds in his right hand at the end of the chain, and take another from his left; but if he is not in a straight line with the mark, the follower must direct him with his left hand by moving it to the right or left, as may be necessary, till he is in the proper direction; then the follower must move his hand downward as a signal for the leader to put down his arrow. That being done, the leader must fix his eye upon the mark he is going to, and endeavour to go straight towards it, a chain farther, and then the follower will come to the place where the leader put down the first arrow; this he must take up after the leader has put down another in the proper direction. In this manner they must proceed till the whole line is measured, and when they come to the end the arrows in the follower's hand must be counted, and also the number of odd links, if there be any, between the last arrow and the end of the line. If the line, however, be more than eleven chains in length, it will be necessary for the leader and follower to change arrows-that is to say, when the leader has put down the tenth or last arrow, and gone a chain farther, the follower, after taking up the arrow, must come forward and carefully count to him the ten arrows which he has taken up, and one of them being put down at the end of the chain, they must proceed with measuring the next ten chains, and so on, till the whole line is finished. To be particularly careful in counting the arrows at each change, and also at the end of the line, and if any of them are missing, the line must be measured over again. When the line is of great length, a mark should be set up at each change, so that in case any of the arrows are lost, it would be necessary only to measure the last ten chains instead of the whole line. When it happens that there is not quite the length of the chain between the last arrow and the end of the line which you are measuring, the leader may fix the end of the chain at the station-staff or mark, and hold it there till the measurer comes to the last arrow; then, by stretching the chain, he will be able to reckon the odd links by help of the brass marks beforementioned, without going to the end of the line, or trusting to the assistant to reckon them for him. Suppose for instance, that the measurer, when standing at the last arrow, finds the distance between it and the end to be one, two, or three tens, and some odd links, past (or more than) fifty, then the distance will be 60, 70, or 80, together with the odd links. A day's practice in the field will render a learner quite perfect in counting the surplus links. The measurer, when giving directions to the chain-leader to keep in a right line with the mark, must have his eye and chain-hand directly over the arrow which sticks in the ground, and must take care that the leader places his arrow perpendicularly and in a direct line with the object of direction, or else the distance will be made longer than it really is, a straight line being the shortest way from one point to another. When the leader has put down his arrow he must keep his eye fixed upon the mark at the end of the line, as he moves forward, which will save the measurer a great deal of trouble in keeping him straight; for he cannot possibly deviate much. from the proper path if he keeps the mark in view as he moves forward. With these preliminary instructions, which are indispensably necessary to be observed, to obtain correct results, I will now give you the rules and directions for measuring with the chain and cross-staff, all manner of straight sided fields, whether square, rectangular, triangular, quadrangular, or multangular, and casting up the contents of the same with the pen. The quantity of land in any field or estate, is estimated by the number of square chains contained in its surface, and those square chains are afterwards reduced to acres, roods, and perches. An acre is equal to ten square chains, or to a space ten chains in length and one in breadth, which is divided into four equal parts called roods, and each rood is divided into forty equal parts called poles or perches. The divisions of land-measure are therefore as in the following table: The length of the line measured with the chain are set down in chains and decimals, the odd links being so many hundredth parts of a chain, therefore the content, when found, is in square chains, and must be divided by ten, (or the decimal point must be removed one place to the left-hand) to bring it to acres. The decimal part must then be multiplied successively by four to bring it to roods, and by forty to bring it to perches. Some surveyors, however, pursue a different practice, and set down the whole number of links as integers, the content, when found, is then in square links, which are reduced to acres by dividing by 100000, or by cutting off five figures from the right hand for decimals. When a chain is not at hand, or when small pieces of land are to be measured, the dimensions may be taken in yards, or in feet and inches, with a measuring tape; and when the content is found in square yards it is reduced to acres by dividing by 4840, the number of square yards in an acre. PROBLEM I. To find the area of a square whose side is 14 chains 20 links. To find the content. Rule:-Multiply the side by itself and reduce the product to acres, roods, and perches. To find the content of a rectangular piece of ground whose length is 16 chains 64 links, and breadth is 7 chains 44 links. Rule:-Multiply the length by the breadth, and the product will be the content. To find the content of a piece of ground in the form of a rhombus (diamond shape) 6 chains 64 links long, and 2 chains 20 links perpendicular height. Rule: Multiply the length by the perpendicular breadth or height, and the product will be the area. To find the content of a piece of ground in the form of a Trapezoid, that is a plane four-sided figure having two of the opposite sides parallel to each other, one side 5 chains 20 links, the other side 8 chains 14 links, and the base 16 chains 64 links required the content. Rule-Multiply the sum of the perpendiculars, or parallel sides, by the distance between them, and take half the product. 8.14 To measure and find the content ofa triangular field whose base is 6 chains 50 links, and perpendicular height 5 chains 60 links. Rule:-Multiply the base by the perpendicular height and half the product will be the area; or multiply the one of these divisions by half the other. 6.50 6.50 2.80 52000 13000 10) 1.82000 R P 3 11 |