when she came into the water, that it would not support her upright, but she sallied and laid down on one side, with the black strake a∣bove the bends amidships in the water, this frightened the people upon deck, and all getting upon the upper side, she then sallied or rolled over as low the other way, and the people as before shifted themselves to the contrary side, which made her keep constantly thus sallying, whilst they towed her with boats about half a mile, and got her to a side, where the people gladly got out of her.
SHE was launched without her rudder, and I had the opportuni∣ty of being near her, and observed a boat under her stern that was held by a man with the boats stem close to a rudder-band, about three feet above the water's edge, which rudder-band I perceived to have little or no motion, but was the axis of the center of gra∣vity, and motion, that she turned upon, while she was thus sallying or rolling, with her upper works in the water, which I reckoned was as high above water, as the keel was under water amidships, when the ship was upright.
CAUSES are best discovered by their effect, from experience and observation we must find out true principles. This ship's sharp bot∣tom in the water, when she was upright, made too small a base, and the center of cavity lay too low, to support her upright, with the center of gravity lying so high above water, that it made her sally or lie down on one side, till that brought a broader base into the water, and the center of cavity (then immersed) higher up, and farther over, and without the center of gravity, so that the center of cavity then became as a prop, to support the ship from going lower, as she sallied each way, and in this case, the center of cavity was the center of motion, that she turned upon, when her side was laid down; for all the weight and power that was without the cen∣ter of cavity acted as a lever, the same as when ships are hove down keel out, that lifted the center of gravity a little, as she sallied, which soon preponderated again, and the people always moving over to the upper side, accounts for this ship's sallying.
THIS ship's behaviour, and the above experiments, in my opinion, make it evident, that the center of motion of a ship, is at the center of gravity, and according to the built of the ship, and her center of gravity, being higher up or lower down, the different properties or behaviour of ships, may be accounted for; from the construction of the above ship, when loaded with refined salt, that just fil'd her, the center of gravity being then a great height, the report of her performance at sea was that she answered very well, and