Various units of length, varying with the fiber, used in determining measures of fineness of yarn.
A 120yard length of cotton yarn, = ¹⁄₇ of the 840yard hank.
hank 

lea 
7 

thread 
80 
560 

54 inches, or 1½ yards 
120 yards 
840 yards 
The fineness of cotton yarn was expressed in counts, the number of 840yard hanks needed to weigh 1 pound avoirdupois. In practice, however, it was easier to weigh one or more leas than a hank. The lea was weighed in troy ounces, the units used for precious metals. One troy ounce = 20 pennyweights (dwt); 1 pennyweight = 24 grains (gr); 1 grain = 4 quartergrains (qr); and 1 "dc" = a tenth of a quarter grain, which is 0.0016 grams. The lea was weighed in these units.
To do the math, weavers resorted to tables that converted the mass of the lea in troy measure to the number of hanks in a pound avoirdupois, that is, the fineness of the yarn in counts.
Eventually, scales were devised which enable the count to be read directly from the scale.
1. W. Etchells.
The Cotton Spinners Assistant.
Manchester: Printed and sold by M. Wilson...and also by Messrs. Clarkes...and by Mr. T. Sowler..., and by the Author, 1820.
2. Norman Biggs.
Applicable mathematics in the 18ᵗʰ century: an example from the textile trade.
Talk given at the IMA History of Mathematics Conference 6 November 2009.
Online at https://pdfs.semanticscholar.org/a8c8/847b96dc85572724e8834f222a7b1cbce05a.pdf
Also called a rap.
1
By these tables the most unlearned may without the help of figures, ascertain the exact average, length, or fineness, of any set of yarn, that is spun on a mule or jenny of any number of spindles from 84 to 300, by the wrapping of one cop and the weight of the whole set. But where the greatest exactness is required, wrap two or three cops out of a set and then take their average length, which will be found a certain method of ascertaining the exact fineness of yarn in the cop, for weighing by penny weights and grains, one, two or more leas as is now most generally in use, is found to be a very inaccurate and deficient way, for there is scarce two leas on a set or even on one cop that will weigh exactly alike, or suppose that every lea or even every hank in a set weighs exactly the same, we cannot suppose so small a quantity as seven leas, could be weighed to so great a nicety, as to be certain, for instance, that 150 would weigh one pound, and if only one lea was weighed, as is frequently the case, it would take 1050 to make a pound of 150 hanks in the pound, and we believe it next to an impossibility to weigh a quantity of yarn at 1050 times, and say it shall be exactly one pound, nay indeed repeated trials prove to us that even at 80 or 100 hanks in the pound it will sometimes vary 10 or 12 hanks. These defects shewed us the necessity of instituting some other plan, by which we could more accurately ascertain the length or fineness of yarn in the cop.
[No author]
The Assistant Calculator, or, Cotton Spinner's Guide, being a complete Set of Tables, of the Greatest Use in the Cotton Spinning Business. Rendered as concise, plain, and simple as possible, with a full explanation to the whole.
Manchester: Printed and sold by W. Shelmerdine and Co., 1799.
Page iv.
2
A yarn number for cotton, the number of 120yard lengths needed to make up a pound. Thus the higher the number, the finer the yarn.
ASTM Standard D12303. Standard Terminology Relating to Textiles.
Edition approved 10 February 2003.
worsted wool, 80 yards.
A 120yard length of spun silk.
A yarn number for wetspun linen yarn, the number of 300yard cuts needed to make 1 pound avoirdupois. Thus the higher the number, the finer the yarn. See yarn numbers.
ASTM Standard D12303. Standard Terminology Relating to
Textiles.
Edition approved 10 February 2003.
Copyright © 2000 Sizes, Inc. All rights reserved.
Last revised: 16 August 2020.