LAND SURVEYING. Land Surveying is that art which enables us to give a true plan or representation of any portion of land, and to determine its superficial contents. In measuring land, the superficial content or area is always expressed in acres, and decimal parts of an acre, or in acres, roods, and perches; each acre containing 4 roods, and each rood 40 perches. The land surveyor must be provided with instruments accurately constructed; and he must always take particular care that they be properly adjusted. The principal instruments required, are straight poles shod with iron spikes, so as to be easily driven into the ground; a chain to measure distances; a cross-staff to erect perpendiculars; and a theodolite to measure angles. The instruments required in plotting, &c. will be noticed hereafter. The chain most generally used is Gunter's, which is 4 poles, or 22 yards, or 66 feet in length, and is divided into 100 links, each link being of a yard, or 66 of a foot, or 7.92 inches. 100 00 At the end of every tenth link is attached a piece of brass (each of a different shape ;) and sometimes at the end of every fifth link, a piece of iron, for more readily counting the additional links. An English L acre contains 4840 square yards, 160 square perches, 10 square chains, 100,000 square links. To reduce acres, roods, and perches to links, multiply the acres by 100000, the roods by 25000, and the perches by 625. In 46A. 3R. 12P. how many square links. 46×100000=4600000 3× 25000 75000 12X 625= 7500 4682500 square links. The In measuring with the chain, the lengths of lines are generally set down in links, as integers: therefore the content is found in square links, which is readily reduced to acres by cutting off five of the figures on the right-hand, towards the left, for acres. decimal figures are reduced to roods by multiplying by 4, and cutting off five figures as before, for decimals, which decimal part is reduced to perches by multiplying by 40, and cutting off five figures from the product. Example.-Suppose the length of a rectangular piece of ground to be 573 links, and its breadth 425; required the number of acres, roods, and perches it contains. The decimal cut off amounts to more than a perch, which may be included in the contents, if the ground be of such value as to make it a matter worth claiming. The statute perch is 5 yards or 16 feet; but the Irish perch, called a plantation perch, is 7 yards or 21 feet. Hence the length of a plantation chain is 1008 inches. When an Irish chain is used, the content is found in links, as before, which is reduced to acres, roods, and perches, by the same process employed above. Hence it appears that an Irish acre is greater than an English acre in the proportion of 121 to 196, an English acre being 4840 square yards, and an Irish acre 7840 square yards, which by reduction, are to each other in the proportion of 121 to 196. To Reduce Statute Measure to Plantation Measure, and the contrary. RULE. Multiply the acres by 842 121, and divide by 196, and the 196) 101882(519 acres. quotient will give the plantation measure. EXAMPLE. Let it be required to reduce 842 acres, statute measure, to plantation measure. Note. The first remainder, 158, is multiplied by 4, and the product divided by 196, which produces 3 roods, leaving a remainder of 44, which is multiplied by 40, and the product divided by 196, as before, giving 848 perches. 980 388 196 1922 1764 158 632(3 roods. 44 40 1760(848 perches. 1568 192 196 = To reduce Plantation Measure to Statute Measure. RULE.-Multiply the area in Irish measure by 196, and divide the product by 121, and the quotient gives the acreage in statute measure. EXAMPLE. Let it be required to reduce 519A. 3R. 848P. Irish measure to English measure. Note. The acres, roods, and perches are multiplied by 196, by compound multiplication, and the product is divided by 121. Before the survey is commenced, a standard distance of 66 feet should be laid down in some convenient place, in order to ascertain the exact length of the chain every morning, and register its error, if any there be, in the field book. The chain used in the common practice of surveying generally stretches: when this is the case, a ring or two is taken off, to reduce it to the proper standard of 66 feet. |