APPENDIX A.

IT may be thought that I should have included under the head of the weights, the weight of the hull. This would have been to have given value to a defect-as, all other things being equal, the lighter the hull the better. As amongst other reasons, that which occurs in the case of the Eurydice as compared with the Carysfort's class and form. She is 50 tons lighter than the Carysfort, and can therefore take 50 tons more water and provisions under the same displacement as them.

This, of course, is only a defect when the hull is heavier of necessity, as when the breadth is great the scantling must be greater to have equal strength with that of vessels which have less breadth.

It may arise from an accidental circumstance, as in the Barham, Vindictive, &c. because of their having been two-decked ships, and in such case is unfavourable to the ship, and should be allowed.

It is most desirable that competing ships should be as nearly alike as possible in all respects, except in form, as it is quite impossible to measure exactly the consequences of disparities, for even in that of the difference in the amount of sail, though it be (approximately) true, that the velocity varies as the square root of the power, yet it is only so when all other things remain the same, which is hardly possible in practice, as every alteration in the amount of sail is attended with an alteration in the point of application of this power, therefore it will act with more or less effect, as may be; and by this, the same ship only can be compared with herself, and not ships differing in form, in height of the centre of effort of

the sail, in weights, and in the arrangement of these weights.

I said this was only the approximate law, because it is only an approximation founded upon an approximation— for it is upon the supposition that the resistance varies as the square of the velocity, and this is found to be true only under certain circumstances.

pressure of wind on a square foot of sail when

blowing with the velocity of one foot. pressure of water against a square foot at the same velocity.

effective area of the sails.

the area against which the pressure of the

water acts.

velocity of wind.

velocity of ship.

The relative velocity of wind and ship = v-V, and

For the same reason the resistance = p′ B V2.

Hence Ρ A (v—V)2 = p' B V2

If now

we want to approximate we may neglect

✓ p A in the denominator, and in such case V

VV p A

=

v.

Vp' B

or velocity of the ship would, cæteris paribus, vary as the square root of the area of the sails; but this can only be regarded as an approximation.

APPENDIX B.

A COPY OF MR. FINCHAM'S REPORT.

"PORTSMOUTH YARD, 15th Feb. 1846.

"THE 'wave line,' as a principle in the construction of vessels, which has been advocated by Mr. Russell Scott,* appears to be the principal feature in the proposed design, and vessels formed on this principle appear to have had some advantage in the experiments which he made. But as these experiments were not made under the circumstances to which sailing vessels are subject in a heavy sea, it does not seem clear that we may infer with much confidence from them, what degree of excellence such a form would possess in the greatly altered circumstances in which vessels must inevitably be placed, for the form which is opposed to the resisting medium is continually varying as the extremities are alternately elevated and depressed in a heavy sea. From these considerations I would respectfully submit, that the waved form and extreme sharpness of the bow, should be very carefully and deliberately considered before being given to ships carrying heavy weights, especially as in the form now under consideration, the adjustment of the fore and after bodies, is the reverse of what experience has shewn to be essential to a good ship, and which must subject a ship to uneasy motions, and also render the

* He means Mr. Scott Russell.

due effect of the rudder a very questionable matter. Experience has frequently shewn that vessels with a very full after-body, requiring great weight to bring them by the stern, have been uneasy in a sea, and have also steered badly. If an analysis were formed of the different ships in the British navy, it would be perceived by the great diversity of form as to the degrees of fulness and sharpness at the extremities, and it would also at the same time appear that there is in all good ships, a proper relation between the fore and aft bodies, and that where this has not been the case, the ships have always been subject to uneasy motions of pitching and scending.

"The motion of rolling and lurching depends chiefly on the transverse form of the body, and on this point it would be found under analytical examination, that when too much of the body has been thrown in by the lee lurch whilst there has not been enough body below water to catch the ship on the weather lurch, the ships have invariably rolled with an uneasy motion, except on a wind, and under a press of sail. All these effects are comparative, being confined with limits, but the degrees can be ascertained only by comparing the forms of ships which have been tried at sea. Uneasy motions in rolling may result likewise from inclination, throwing in more of the after-body than the fore-body, causing the ship to revolve on an axis somewhere between the longitudinal and the transverse axis, and this would be the case with the construction now under consideration. I have made the preceding observations with the view merely to shew, that the conclusions which I have drawn are derived from the experience and observation of ships that have been already tried, and I beg to state also, that

in order to form a just estimate of the character of the proposed construction, I have made an analysis of the bodies of several frigates, and I find the relation of the fore-body to the after-body from the middle of the waterline, in the Endymion after-body is as

"From this statement it is seen, that proportion of the after-body in the proposed construction, greatly exceeds that in any of the other ships, and consequently there must be a great excess of weights to bring the ship to her intended water-line. This must of necessity render the momentum of inertia abaft greater in proportion to that forward, and cause not only an uneasy motion to the ship in pitching, but likewise cause her inevitably to steer badly, since in all the other ships the centre of gravity of the displacement is before the middle, as all constructors consider it should be, whilst in the proposed construction it is 4 feet abaft. The same may be shewn by an examination of all the elements which affect the motions of a ship, and which will be seen by referring to the table in which the elements of construction are given. And perhaps the form may be more clearly seen by lines formed by the areas both of the vertical and horizontal sections, which I hope will give a clear view of the relative form of this ship, in comparison. with the forms of ships which have been tried.

"After having given to this construction the best con

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