HISTORY OF MARINE ARCHITECTURE.

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in order to allow the greater purchase for working the oar. If the handle is impelledby the rower from a to b, and thence raised to c , it will then take the water ;and being pulled back forcibly on the line c a, will, as a natural consequence,produce its share of impulse on the vessel. Of the two rowers who work thesecond tier, the highest and innermost is placed seven feet within board, andthe seat being raised as many inches above the row-port, the handle of the oarthey work will describe the lines d e f. Of those in the third tier, the inner-most and highest will be raised ten inches above its row-port, and as many feetwithin it, the handle of their oar describing the triangle g h i. Preservingthe like proportion, the upper rower in the fourth tier sits thirteen inches abovethe row-port, and as many feet within it, he will have to move the handle k to /,and from thence to ?n, where it will meet the water. The interior rower in thefifth tier is seated sixteen inches above the port, and as many feet within it,and extending his oar handle from n to o , and from thence to Ji, will, by draw-ing it back with spirit, produce the effect required of him. Let us imagine allthese tiers to have been placed under the upper deck : the sixth and uppermostwas, as may be supposed, worked on the upper deck itself, the innermost row'ersitting nineteen feet within the port, and as many inches above it; but thoughstill so much more elevated above the surface of the water, this was a task ofno more difficulty and labour than that of working those in the fifth tier, becausethe handle of the oar being raised to the height of the line q q , might be broughtdown from any point thereof to its first station with much greater ease than inany of the lower tiers, in which it was absolutely necessary that the extremityof the handle of each oar should describe fixed and determinate lines, inasmuch as,otherwise, the stroke would have been interrupted by the seats, or what was ofstill worse consequence, the rowers would have impeded each other.

It must appear very evident, on inspecting this, and the diagram, Fig. i,that it was scarcely possible to extend the tiers of oars, rising above each other,,to more than six ; not only because the operation of rowing must become nearlyuseless, on account of the great degree of elevation to which it was necessaryto bring the handle of the oar in order to form the stroke, but also, as the oarswould of necessity become so long as to be unmanageable, even if the objectionfirst mentioned did not exist.

That it may be, if possible, ascertained still farther, with something like pre-.cisiou, how many benches, or ranks of oars there were in a ship of the largestrate, and how many rowers could with convenience sit on, each bench, let us. I 2 take