The barleycorn (one-third inch.) is an old unit still surviving in shoemakers shoe sizes, these being graded by thirds of an inch or bar leycorns, in a system of 13s.
Four units based upon the °hands are some times used. These are the nail (two and one fourth inches) for measuring cloth, originally the distance from the end of the thumb nail to the joint at the base of the thumb, and later fixed as 1-16 yard; the palm (three inches) ir.cludes the breadth of the hand exclusive of the thumb; the hand (four inches), originally the breadth of the palm, is used in measuring • horses and is almost exactly one decimetre; the finger (four and one-half inches) is about the length of the middle finger and is only used as a rough unit in cloth measure. This should not be confused with the finger breadth used in measuring charges of powder.
The surveyor's link (7.92 inches) is the length of one link or 1-100 part of a surveyor's chain, and is used in the survey of lands.
Quarter (nine inches) is sometimes used in measuring cloth (more frequently in Great Britain) to designate a quarter of a yard. A unit of the same length called the span was originally half a cubit, but probably has not been used in modern times as an officially recog nized unit.
The engineer? link (12 inches) used as a unit in engineering is the hundredth part of the engineers' chain and is decimally divided. The 10th of the engineers' link is 12 inches.
The pace is a conventional unit for measur ing distances and is the length of a stride meas ured from the heel of one foot to that of the other ,• a full pace measures about one yard. This is the value of the United States military pace, double time, with a cadence of three steps a second. 'The regulation military pace quick time is 30 inches with a cadence of two steps per second. The Roman pace was a dou ble step of about five feet.
The English ell, a unit still referred to but seldom used, having a value of 45 inches, vary ing, however, in different places. The Flemish ell of 27 inches is still in use commercially in the Low Countries.
The fathom (six feet) is used in measuring depths of water or mines. The name conies from an Anglo-Saxon word faethm, signifying 'embrace.' and originally meant the length of rope between the two hands when the arms were held outstretched.
The rod, perch or pole is equal to five and one-half yards and is used in measuring land. It has varied in different places from five to eight yards and is supposed to have been the length of the ancient goad used to measure the width of the first furrow.
The surveyors' or Gunter's chain (22 yards) was so chosen that 10 chains square might ex actly equal one acre This chain is the official unit prescribed formerly for the use of stir surveying public lands under the super vision of the surveyor-general and now often used in relocating old surveys.
The engineers' chain (100 feet) is used in engineering, and is decimally divided into feet. tenths and hundredths of a foot. The use of the two chains in many cases for the same land for different purposes requires reduction tables. On account of the direct relation to the foot, the engineers' chain is becoming very widely used.
The bolt for measuring cloth is generally given as 40 yards. though the name means sim ply a roll of definite length. The customary length of the bob varies with different fabrics and manufacturers.
The skein for yarn is often defined as 120 yards. Its length varies, however, according to the material and the locality. Consult the United States Conditioning and Testing Com pany's tTextile Tables' (New York 1914).
The United States cable's length (720 feet), used by mariners, is 120 fathoms as recognized by the United States navy.
The furlong (220 yards) originally meant 'length of a furrow,' supposed to be the dis tance oxen ,could plow without stopping to rest.
The hank is a unit of length for yarn. In the United States the length of a hank of cot ton is usually 840 yards, while that of linen is 3,000 yards; different lengths, however, are also in use under that title.
The nautical mile or geographical mile has been defined as 1-60 part of the length of a degree of a great circle of the earth. Since the earth is not a perfect sphere, however, the de gree varies in length and this has led to much confusion in usage regarding the nautical mile. The definition accepted by the United States Coast and Geodetic Survey (consult Report of 1881, Appendix 12) is as follows: The 1-60 part of the length of a degree on the great cir cle of a sphere whose surface is equal to the surface of the earth. This makes the length of the nautical mile 6,080.20 feet or 1,853248 metres. The uncertainty in the dimensions of the earth affects the last decimal place given. The nautical mile is often miscalled *knot.* The latter term, however, is not a measure of length, but a measure of speed, equal to one nautical mile per hour. The admiralty 'knot' of Great Britain is 6,080 feet.