TIMBER. To find the Area or Superficial Content, of a Plank. + Note. When the Board is tapering, add the breadths at the two ends together, and take half the sum for the mean breadth. Or else, take the mean breadth in the middle. Example. Required the Content of a Board whose length is 11 feet 2 inches, and breadth 1 foot 10 inches. ft. in. ft. in. ft. in. 11 2 X 1 10 20 5. Content required. To find the Solid Content of squared, or four sided Timber. Multiply the mean breadth by the mean thickness, and the product by the length, for the Content nearly. Note 1.-If the Tree taper regularly from the one end to the other, either take the mean breadth, and thickness, in the middle, or take the dimensions at the two ends, and half their sum will be the mean dimensions; which multiplied as by the above Rule, will give the Content nearly. Note 2.-If the piece do not taper regularly, take several different dimensions, add them all together, and divide their sum by the number of them, for the mean dimensions. Example. Required the Content of a piece of Timber 16 feet long, and side of square 14 inches. ft. in. ft. in. ft. ft. in. Content required. To find the Solidity of round, or unsquared, Timber. Multiply the square of the quarter girt, (or the square of of the mean circumference) by the length, for the Content. Note. When the Tree is tapering, take the mean dimensions, either by girting it in the middle for the mean girt; or at the two ends and taking half the sum of the two; or by girting it in several places, then adding all the girts together and dividing the sum by the number of them for the mean girt. But when the Tree is very irregular, divide it into several lengths, and find the content of each part separately. Example. Required the Content of a Tree, whose mean girt is 3.15 feet, and length 144 feet. To find the Weight of a Tree. Find its Content in feet, and multiply that by the Specific Gravity of the Wood. Vide Table of Specific Gravities. Example. Required the Weight of an Elm tree whose mean girt is 5 feet, and length 60 feet. 1.25 1.25 X 1.25 = 1.5625 1.5625 X 60 93.75 Content in feet. (Specific gravity of Elm 540) × 93.75 50625 ounces= 1 Ton 8 cwt. the Weight required. Note. Oak weighs about 50 lb. per cubic foot. с с TONNAGE. To ascertain the Tonnage of Sailing Vessels, Rule. Divide the length of the upper deck between the afterpart of the stem, and the forepart of the sternpost into six equal parts. Depths: At the foremost, the middle, and the aftermost of those points of division, measure in feet and decimal parts of a foot the depths from the under side of the upper deck to the ceiling at the limber strake. In the case of a break in the upper deck, the depths are to be measured from a line stretched in a continuation of the deck. Breadths: Divide each of those three depths into five equal parts, and measure the inside breadths at the following points: viz. at one fifth and at four fifths from the upper deck of the foremost and aftermost depths, and at two fifths and four fifths from the upper deck of the midship depth. Length: At half the midship depth measure the length of the vessel from the afterpart of the stem to the forepart of the stern-post; then to twice the midship depth add the foremost and the aftermost depths for the sum of the depths; add together the upper and lower breadths at the foremost division, three times the upper breadth and the lower breadth at the midship division, and the upper and twice the lower breadth at the after division, for the sum of the breadths; then multiply the sum of the depths by the sum of the breadths, and this product by the length, and divide the final product by 3500, which will give the number of Tons for register. If the Vessel have a poop or half deck, or a break in the upper deck, measure the inside mean length, breadth, and height of such part thereof as may be included within the bulk-head; multiply these three measurements together, and dividing the product by 92'4, the quotient will be the number of tons to be added to the result as above found. * Note. The calculation of Tonnage for Baggage, Stores, &c. is by measurement, a Ton consisting of 40 cubic feet: but Metals and very heavy articles are estimated for by actual weight, without reference to bulk. In order to ascertain the tonnage of open vessels, the depths are to be measured from the upper edge of the upper strake. To ascertain the Tonnage of Steam Vessels. Rule. In each of the several rules herein-before prescribed, when applied for the purpose of ascertaining the tonnage of any ship or vessel propelled by Steam, the Tonnage due to the cubical content of the Engine room must be deducted from the total tonnage of the vessel as determined by either of the rules aforesaid, and the remainder will be the true register Tonnage of the said Ship, or Vessel. To determine the Tonnage due to the cubical Content of the Engine Room. Rule. Measure the inside length of the Engine room in feet and decimal parts of a foot from the foremost to the aftermost bulk-head, then multiply the said length by the depth of the ship or vessel at the midship division as aforesaid, and the product by the inside breadth at the same division at two fifths of the depth from the deck taken as aforesaid, and divide the last product by 924, and the quotient will be the Tonnage due to the cubical content of the Engine room. To ascertain the Tonnage of Vessels when laden. Rule. Measure, first, the length on the upper deck between the after part of the stem and the forepart of the stern-post; secondly, the inside breadth on the underside of the upper deck at the middle point of the length; and, thirdly, the depth from the underside of the upper deck down the pumpwell to the skin; multiply these three dimensions together, and divide the product by 130, and the quotient will be the amount of the register Tonnage of such Ships. MECHANICS. Mechanics is the Science of Forces, and the effects they produce when applied to Machines in the motion of bodies. Machine, or Engine, is any mechanical instrument contrived to move bodies. Mechanical Powers are certain simple instruments commonly employed for raising greater weights, or overcoming greater resistances than could be effected by the natural strength without them. They are usually accounted Six in number; viz.: The Lever; the Wheel, and Axle; the Pulley; the Inclined Plane; the Wedge; and the Screw. Weight, and Power when opposed to each other, signify the body to be moved, and the body that moves it; or the Patient, and Agent. The Power is the Agent, which moves, or endeavours to move, the Patient, or Weight. Equilibrium is an equality of action, or force, between two or more powers, or weights, acting against each other, by which they destroy each other's effects, and remain at rest. The Centre of Motion is the fixed point about which a body moves. The Axis of Motion is the fixed line about which it moves. The Centre of Gravity is a certain point on which a body (being freely suspended) will rest, in any position. The whole Momentum, or quantity of force of a moving body is the result of the quantity of matter multiplied by the velocity with which it is moved; and when the product arising from the multiplication of the particular quantities of matter in any two bodies by their respective velocities are equal, their momentum will also be so. Upon this simple principle depends the whole of Mechanics; and it holds universally true, that when two bodies are suspended on any machine so as to act contrary to each other; if the machine be put in motion, and the perpendicular ascent of one body multiplied into its weight, be equal to the perpen |
