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 addition to the foregoing rules, 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 bulkhead, 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 of the same division at two-fifths of the depth from the deck, taken aforesaid, and divide the last product by 92·4, 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 afterpart of the stem, and the forepart of the stern-post; secondly, the inside breadth on the under side of the upper deck, at the middle point of the length; and, thirdly, the depth from the under side of the upper deck down the pump-well to the sink; 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.