This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.
In order to ascertain the contents, multiply the square of the quarter girth, or of 1/4 of the mean circumference, by the length. When the buyer is not allowed his choice of girth in taper trees, he may take the mean dimensions, either by girthing it in the middle for the mean girth, or by girthing it at the two ends, and taking half of their sum. If not, girth the tree in so many places as is thought necessary, then the sum of the several girths divided by their number, will give a mean circumference, the fourth part of which being squared, and multiplied by the length, will give the solid contents.
The superficial ft. in a board or plank are known by multiplying the length by the breadth. If the board be tapering, add the breadth of the two ends together, and take-half their sum for the mean breadth, and multiply the length by this mean breadth.
The solid contents of squared timber are found by measuring the mean breadth by the mean thickness, and the product again by the length. Or multiply the square of what is called the quarter girth, in inches by the length in feet, and divide by 144, and you have the contents in feet.
Boughs, the quarter girth of which is less than 6 in., and parts of the trunk less than 2 ft. in circumference, are not reckoned as timber.
1 1/2 in. in every foot of quarter girth, or 1/8 of the girth, is allowed for bark, except of elm. 1 in. in the circumference of the tree, or whole girth, or 1/12 of the quarter girth is the general fair average allowance.
The quarter girth is half the sum of the breadth and depth in the middle.
The nearest approach to truth in the measuring of timber is to multiply the square of 1/5 of the girth, or circumference, by double the length, and the product will be the contents.
100 superficial feet of planking equals 1 square.
120 deals " l hundred.
50 cub. ft. of squared timber " 1 load.
40 ft. of unhewn timber „ 1 load.
600 superficial ft. of 1-in. planking „ 1 load.
A fir pole is the trunk of a fir tree, 10-16 ft. long.
Battens, deals, and planks, as imported into this country, are each similar in their various lengths, but differing in their widths and thicknesses, and hence their principal distinction; thus, a batten is 7 in. by 2 1/2 in. a deal ,, 9 „ 3 „ a plank „ 11 „ 3 „ these being what are termed the standard dimensions, by which they are bought and sold, the length of each being taken at 12 ft.; therefore, in estimating for the proper value of any quantity, nothing more is required than their lineal dimensions by weich to ascertain the number of times 12 ft. there are in the given whole. Thus - if purchasing deals -
7 of 6 ft.
5 „ 14 "
11 „ 19 " and 6 " 21 "
6 X 7 = 42 ft. 14 x 5 = 70 " 19 x 11 = 209,, 21 X 6 = 126,,
12)447(37.25 standard deals.