TO MEASURE AND COMPUte the solidITY OF SQUARE TIMBER, AS RECEIVED INTO THE KING'S AND OTHER YARDS. + As, in consequence of the great irregularity in the growth of that timber which is most useful in ship-building, the taking a mean out of several girths or dimensions is not sufficiently accurate, the method that is used in the King's and other yards is, to measure the tree into as many lengths as the measurers shall judge proper; (that is, they mark off the different lengths as far as the tree regularly tapers ;) and then find the contents of each length separately, and add the whole together; thus are the contents of the whole tree obtained, with branches or boughs measuring two feet compass, or six inches girt, which are reckoned as timber; their solidity being computed and added to that of the tree: but, so much of the trunk, boughs, or branches, as measure less than six inches, are not esteemed timber, and therefore not added to the other contents. RULE 5. Measure the tree into as many lengths as may be judged necessary, then find the contents of each length as follows: when the lengths are set off, take the size of the tree upon the parts that are squared both ways, and exactly in the middle of each length; then add the two squares together; next take one half, which will give a mean square ; multiply the mean square by itself, and the product by the respective length, the last product will be the contents: next add the contents of every length so found, and the total will be the solidity of the whole tree in feet; which, being divided by 50, the quotient will be the number of loads contained in the whole tree or number of trees. NOTE 1. The mean square is a geometrical mean proportional between the mean breadth and thickness; that is, the square root of their product. Sometimes unskilful measurers use the arithmetical mean instead of it, that is half their sum; but this is always erroneous; and, the more so, as the breadth and depth differ the more from each other. EXAMPLE. Required the solidity of a tree, whose dimensions are as follow first length 18 feet; the square 16 inches by 18 inches; second length 12 feet; square 14 inches by 12 inches; third length 10 feet; square 10 inches by 8 inches; one branch, length 9 feet; square 8 inches by 6 inches; and another branch, length 8 feet; square 9 inches by 7 inches. The calculating of the dimensions by figures as above, shews the exact contents of the tree (according to the rule observed) to the twelfth part of an inch; but, as that would be so very tedious in measuring timber for sale, or in receiving it into store, the measurers, for quick dispatch, make use of the sliding rule; by which they calculate no nearer than to the half of a foot in the contents of each length; but that will be of little or no consequence; because the loss thereby will not be more than the odd inches in the above tree. After finding the contents of each length, by the sliding rule, they proceed as before, by adding them all into one sum for the contents of the whole. TO FIND THE CONTENTS OF EACH LENGTH BY THE SLIDING RULE. As 12 on the girt line, is to the length on the slider; so is the mean square on the girt line, to the contents on the slider. 1 TO MEASURE AND COMPUTE THE SOLIDITY OF THICKSTUFF AND PLANK, As received INTO THE KING'S AND OTHER YARDS. RULE. Multiply the whole length of the plank by the breadth taken correctly in the middle, and the product will be the superficial contents ; then, to find the solidity or number of loads contained therein, look for the thickness of plank or thickstuff, as given in a foregoing table, in this section, under which will be found the feet in a load, or divisor for dividing the superficial contents in feet, in order to give the solidity in loads. EXAMPLE 1. Required, the number of loads contained in a piece of 10-inch thickstuff, the length of which is 49 feet, and the breadth, taken in the middle, 1 foot 9 inches. 49 feet x by 1 foot 9 inches is 85 feet 9 inches, which÷by 60 is 1 load 25 feet. EXAMPLE 2. Suppose that there are ten planks of 2 inches thickness, each measuring 24 feet in length, and 13 inches broad in the middle, required the number of loads contained therein ? 24 feet x by 1 foot 1 inch is 26 feet, which x by 10 is 260 feet superficial contents. Then 260 feet divided by 240 is equal to 1 load 20 feet, the solidity required. BY THE SLIDING RULE. As 12 on the slider is to the breadth on the rule, so is the length on the slider to the contents on the rule. In the foregoing examples are contained all the cases that generally occur in the admeasuring of timber for sale; but, when timber is regularly and smoothly hewn, the solidities of such pieces had best be computed by the rules given for prisms, pyramids, cones, &c. and their frustums. In converting timber in the forest, great care should be taken to preserve it as large and as circular as possible, from a consideration of the great use of large and compass timber; but it should be observed, at the same time, to adhere to the custom of squaring it by the rule before mentioned, as, if not so squared, the detriment would not only be in the false measure; but, the defects which might appear, were the timber truly squared, might remain unseen. And, as the defects in timber are of the utmost consequence, it should always be well examined when received or purchased, that the buyer may have an opportunity of having something abated in proportion to the nature of the defect. The defects in timber are various, but it is chiefly owing to the barrenness of the soil, as, in loose and broken ground, the timber is generally shaky, which is a very pernicious defect. Lopping of timber, or the suffering of cattle to browse upon it, often occasions it to rot and decay. But the greatest enemies to the growth of young timber are rabbits; for, where there is a number of these animals, a spontaneous shoot can no sooner appear above the ground but it is destroyed. Sound timber is generally produced in those places where the earth consists of strong clay; for which reason, timber of English growth is found to be so far preferable to that of other countries; for, though some of the best sort of East-country plank is very flexible, and consequently useful for many purposes; yet it is often found very unserviceable, as it is, too frequently, either shaken, foxey, druxy, worm-eaten, or full of rotten knots; therefore, timber of English growth certainly has the preference, even after it has stood so long, that age has made it pliable and past the time allowed for growth, as it is even then allowed to be as durable as any other in its full strength. |