4. The length of a degree of latitude varies, being 68.72 miles at the equator, 68.9 to 69.05 miles in middle latitudes, and 69.30 to 69.34 miles in the polar regions. The mean or average length, as stated in the table, is the standard recently adopted by the U. S. Coast Survey. A degree of longitude is greatest at the equator, where it is 69.16 miles, and it gradually decreases toward the poles, where it is 0. SURVEYORS' LINEAR MEASURE. 280. A Gunter's Chain, used by land surveyors, is 4 rods or 66 feet long, and consists of 100 links. The unit is the chain, and the table is made up of divisors and multiples of this unit. SCALE ch. UNIT EQUIVALENTS. rd. 1. in. 1 7.92 25 198 = 4 = 100 792 80 = 320 = 8000 63360 ascending, 7.92, 25, 4, 80; descending, 80, 4, 25, 7.92. NOTE.—The denomination, rods, is seldom used in chain measure, distances being taken in chains and links. II. SQUARE MEASURE. 281. A Square is a figure having four equal sides and four equal corners or right angles. 282. Area or Superficies is the space or surface included within any given lines: as, the area of a square, of a field, of a board, etc. Thus, a square foot is 12 inches long and 12 inches wide, and the contents are 12 × 12 = 144 square inches. A board 20 feet long and 10 feet wide, is a rectangle, containing 20 × 10: 200 square feet. The measurements for computing area or surface are always taken in the denominations of linear measure. 283. Square Measure is used in computing areas or surfaces; as of land, boards, painting, plastering, paving, etc. The unit is the area of a square whose side is the unit of length. Thus, the unit of square feet is 1 foot square; of square yards, 1 yard square, etc. TABLE. 144 square inches (sq. in.) make 1 square foot,.... sq. ft. yard,... sq. yd. .... .sq. rd. .A. 1 square mile,... sq. mi. UNIT EQUIVALENTS. sq. yd. 301 sq. rd. 1 40 160 sq. in. 144 1296 39204 1568160 4 2560 102400 = 6272640 4014489600 ascending, 144, 9, 301, 40, 4, 640; descending, 640, 4, 40, Artificers estimate their work as follows: By the square foot: glazing and stone-cutting. By the square yard: painting, plastering, paving, ceiling, and paper-hanging. By the square of 100 square feet: flooring, partitioning, roofing, slating, and tiling. Bricklaying is estimated by the thousand bricks, by the square yard, and by the square of 100 square feet. NOTES.-1. In estimating the painting of moldings, cornices, etc., the measuring-line is carried into all the moldings and cornices. 2. In estimating brick-laying by either the square yard or the square of 100 feet, the work is understood to be 12 inches or 14 bricks thick. 3. A thousand shingles are estimated to cover 1 square, being laid 5 inches to the weather. SURVEYORS' SQUARE MEASURE. 284. This measure is used by surveyors in computing the Tp. = 16, 625. 1 640 23040 = P. sq. ch. 1 = = 16 = 10 = 160 = 6400 230400 = 102400 ascending, 625, 16, 10, 640, 36; descending, 36, 640, 10, NOTES.-1. A square mile of land is also called a section. 2. Canal and railroad engineers commonly use an engineers' chain, which consists of 100 links, each 1 foot long. 3. The contents of land are commonly estimated in square miles, acres, and hundredths; the denomination, rood, is rapidly going into disuse. III. CUBIC MEASURE. 285. A Cube is a solid, or body, having six equal square sides or faces. 286. Solidity is the matter or space contained within the bounding surfaces of a solid. The measurements for computing solidity are always taken in the denominations of linear measure. The cubic or solid contents of a body are found by multiplying the length, breadth, and thickness together. 287. Cubic Measure, also called Solid Measure, is used in computing the contents of solids, or bodies; as timber, wood stone, etc. The unit is the solidity of a cube whose side is the unit of length. Thus, the unit of cubic feet is a cube which measures 1 foot on each side; the unit of cubic yards is 1 cubic yard, etc. SCALE-ascending, 1728, 27. The other numbers are not in a regular scale, but are merely so many times 1 foot. The unit equivalents, being fractional, are consequently omitted. NOTES.-1. A cubic yard of earth is called a load. 2. Railroad and transportation companies estimate light freight by the space it occupies in cubic feet, and heavy freight by weight. 3. A pile of wood 8 feet long, 4 feet wide, and 4 feet high, contains 1 cord; and a cord foot is 1 foot in length of such a pile. 4. A perch of stone or of masonry is 16 feet long, 1 feet wide, and 1 foot high. 5. Joiners, bricklayers, and masons, make an allowance for windows, doors, etc., of one half the openings or vacant spaces. Bricklayers and masons, in estimating their work by cubic measure, make no allowance for the corners of the walls of houses, cellars, etc., but estimate their work by the girt, that is, the entire length of the wall on the outside. 6. Engineers, in making estimates for excavations and embankments, take the dimensions with a line or measure divided into feet and decimals of a foot. The computations are made in feet and decimals, and the results are reduced to cubic yards. In civil engineering, the cubic yard is the unit to which estimates for excavations and embankments are finally reduced. 7. In scaling or measuring timber for shipping or freighting, of the solid contents of round timber is deducted for waste in hewing or sawing. Thus, a log that will make 40 feet of hewn or sawed timber, actually contains 50 cubic feet by measurement; but its market value is only equal to 40 cubic feet of hewn or sawed timber. Hence, the cubic contents of 40 feet of round and 50 feet of hewn timber, as estimated for market, are identical. 15 MEASURES OF CAPACITY. 288. Capacity signifies extent of room or space. 289. Measures of capacity are all cubic measures, solidity and capacity being referred to different units, as will be seen by comparing the tables. Measures of capacity may be properly subdivided into two classes, Measures of Liquids and Measures of Dry Substances. し I. LIQUID MEASURE. 290. Liquid Measure, also called Wine Measure, is used in measuring liquids; as liquors, molasses, water, etc. The unit is the gallon, and the table is made up of its divisors and multiples. hhd. = 2016 = 126 = .252 1 = 2 = 63 = 252 = 504 SCALE-ascending, 4, 2, 4, 31, 2; descending, 2, 31, 4, 2, 4. |