PART THE SECOND. TO MEASURE LAND, And find the content without plotting, or ufing a chain. ANY person by half an hour's practice, can ascertain what length in yards he paffes over, in ftepping an hundred paces, and by that means can find the length of any line, by walking over it, near enough for common occafions. This being allowed: The next thing neceffary to be understood, is fome of the properties of a Triangle. The lower fide is called the bafe, and a line drawn from the angle oppofite the base, and falling upon it at right angles, is called a perpendicular. Perpendicular. Bafe. 52 If these two be multiplied together, and the Product divided by 2, the Quotient will be the Content. The length of the Base is easily measured, the only difficulty is in getting a true Perpendicular, to effect which procure a crofs, which may be made of a fquare piece of wood, with two grooves cut across it at right angles. This must be fastened on a Staff about 4 feet long. A crofs made with brafs, on a different con struction to this, but answering the fame purpose, may be bought of Meffrs. JONES, No. 135, Holbörn, London, Price 12s. Measure from A towards B till you think you are oppofite the mark at C, there place the cross at D, apply your eye to one end of the groove, and turn the cross till it is in such a pofition that you can see the mark at A, and the mark B when you look through the other end. Look through the other groove, if you can see the mark at C you are in the right place to measure the perpendicular; if you cannot fee it you must move the cross backwards or forwards, till you are in a pofition to see the three marks through the grooves without moving the cross. Allow the length of the Base to be 145 yards, and the perpendicular 84 yards, the content is found thus 145 Bafe 84 Perpendicular 580 1160 2) 12180 6090 Content in Yards. |