muft point off 5 figures thus, .93930; multiply by 4, point off 5 figures and the left figure is roods 4 3.75720; multiply 40 by 40, and point off 5 fi- N. B. The reafon of pointing off 5 figures to the right is the fame as if the chain and links were fet down and work'd as one whole number, and the product divided by 100000 (the fquare links in an acre) for any number of chains is fo many hundred links: Otherwife if you work the links as the decimal of a chain and divide the product by 10 (the fquare chains in an acre,) the anfwer in acres, &c. will be the fame. PROBLEM II. To measure a four fided field. RULE. Measure round it, putting down each fide feparately; and alfo measure one of the diagonals. EXAMPLE. Suppofe a field in the following form to be measured. I measure the fide A B and find it 5.40, the fide BC and find it 3.20, the fide C D 4.00, the fide D A 6.70, and the diagonal A C 7.20, and its done. To plot the fame. Draw the diagonal A C at random, then take 7.20 from any fcale of equal parts and lay it from A to C; then take 5.40 in your compaffes from the fame fcale, fet one foot in A and defcribe an arch; take 3.20 in your compaffes from the fame fcale, fet one foot in C and cross the former arch in B; draw the lines A B and BC. Then take 6.70 in your compaffes from your feale and defcribe an arch, alfo take 4.00 in your compaffes and crofs the laft arch in D; draw the lines A D and D C, and fo you have the true figure of the field. To find the content. Now let fall perpendiculars to the nearest diftance from the angles B and D upon the diagonal A C, and measure thefe perpendiculars by the fame fcale of equal parts that you ufed before; and it being a trapezium, you may measure it as fuch; viz. multiply half the diagonal by the fum of the two perpendiculars, and in the product point off to the right hand 5 figures only (if you have no decimal parts of a link,) and what remains on the left hand will be acres, &c. See the work in the next page. Perpen To measure a five filed field. RULE. Meafure round it, putting down each fide feparately; and alfo meafure 2 diagonals. EXAMPLE. Suppofe a field in the following form to be measured. I meafure the fide A B and find it 3.20, B, C and find it 6.10, C D 2.90, DE 7.50, and EA 4.00; the diagonal AC I find to be 7.90 and the diagonal A D to be 8.80. To plot it out. Draw the diagonal A C at random, and from a fcale of equal parts take 7.90 and lay it from A to C; take 8.80 from the fame fcale, fet one foot in A, and defcribe an arch; take 2.90 from the fcale, fet one foot in C and crofs the former arch in D; draw the line A D for the fecond diagonal, and the line CD for one fide of the field. Then take 3.20 in your compaffes and defcribe an arch, and 6.ro and crofs that arch in B; draw the lines: A B and B C; take 7.50 in your compaffes and describe an arch, alfo take 4.co and crofs that arch in E; draw the lines DE and AE and you have the true figure of your field. To find the content. Let fall two perpendiculars on the diagonal A D from the angles C and E, meafure their lengths from the fcale of equal parts that you ufed before, and thence find the content of the trapezium A C D E as is before taught. Then let fall a perpendicular from the angle B upon the diagonal A C, find its length from the fcale of equal parts, which multiply by the diagonal A C and you have the content of the triangle A B C, which added to the content of the trapezium A CDE (before found) will give the the content of the whole field as required; remembring to cut off for acres, &c. as before taught. PROBLEM IV. To measure a fix fided field. RULE. Measure round it, and put down each fide separately; and alfo meafure 3 of its diagonals. EXAMPLE. Suppofe a field in the following form to be measured. I meafure each fide and find them the fame as in the figure, and alfo the diagonal A C, A D, and A E, and the field is meafured.. |