'scending can take place, nor can there be any tendency to such

Now, let the water-line be supposed to be brought into the situation CDE, (Fig. 2.) by the action of a wave, let γ be the centre of gravity of the now displaced volume of water CDEFH, into which the whole upward pressure arising from the buoyancy of the fluid may as before be supposed to be collected; the fulcrum of the imaginary lever (in fact, the centre of motion) will then be transferred to y, and consequently the equilibrium destroyed. We have then xxfc representing the tendency of the fore body to descend, zx ab that of the after body to do so, and the difference between these two moments, xxfc-z×ab, (or what is the same thing, the whole weight of the ship multiplied by Gg) will represent the moment which causes the ship to pitch. This point y is then the centre of rotation at the commencement of the vessel's pitching; as the ship's head descends, the water-line CDE approximates to A B, and y approaches to g, with which it coincides when CDE and AB are together: the vessel, however, does not then stop in its descent, the moment of inertia with which it descends (of which I shall have occasion to speak more hereafter) will cause it to plunge deeper forward than the line AB, the line of quiescent floatation, and will consequently bring the pointy to the other side of Gg: when the resistance of the water has overcome this moment of inertia, the ship will begin to ascend forward, commencing its revolution around that point to which y shall ultimately have arrived, and which will again approach to g as the ship approaches to a state of rest.

In the above investigation I have endeavoured to demonstrate that the axis of rotation does not pass through the centre of gravity, that it is not to be found in any fixed point, but that its situation may be determined at any instant of time from the mean direction of the upward pressure of the water at that time, and which is dependent on the then displaced volume CDEFH. The motion of 'scending arises from precisely a similar cause; to produce it, the water must be lower abaft than it is forward, in which case it is evident that y comes before G, the moment z x ab is then greater than xxfc, and their difference, viz. zx ab-xx fc measures the ship's tendency to 'scend.

(To be concluded.)

French or

Engl. Feet.

37

TABLE XXV.

For reducing French Feet to English Feet, and English Feet to French.

THE NEW TONNAGE BILL.

To the Editor of the Nautical Magazine.

SIR,-The vast improvements in progress in our navy, under the direction of the present enlightened surveyor, and the new tonnage bill coming into operation on the 1st of January, which has been framed doubtless with the intention of similar improvements being produced in the merchant shipping of the country, seem to point out this as a fit time for drawing the public attention to such subjects, and induce me, as possessing some experience in nautical matters, to contribute the result of my observations thereon; flattering myself that, as respects men-of-war, they may not be considered unworthy of the attention even of Captain Symonds himself. Moreover, the suggestions contained in these remarks may be found, even by that able and intrepid seaman, such as will tend to complete the work of his own commencement, by extending his improvements, and bringing nearer to perfection the ships of the British navy, already become so infinitely indebted to him for the rapid advances he has made since he succeeded to the influential station which he holds.

Although far from thinking (as will appear in the sequel) that the new tonnage bill is the best measure that could have been devised for the purpose, yet, it being now about to become the law of the land, and all new ships are to be registered thereby ; suffice it to say, that it must be acknowledged a very great improvement on the old method, the effects of which have been so extremely injurious to the merchant shipping of the country, and to the country itself.

I shall, however, point out some defects and inconsistencies in this bill, which, if not speedily obviated, will tend to render it nugatory in its professed views, if not indeed altogether a useless, and perhaps injurious effort of legislation. I think I can shew that erroneous conclusions have been come to, on the effect of the bill in different classes of shipping.

It appears there are 19,110 British registered ships, (I quote from a pamphlet written by one of the committee who formed the bill,) from 50 tons upwards,-that only 3414 of them are above 200 tons. Upon this class (which contains six divisions) it is admitted that the new method of estimating register tonnage will produce a very material nominal increase. The smaller class of vessels are embraced in three divisions, 200 to 100 tons, 100 to 50, and lastly those under 50 tons, the number of which last division is stated to be no less than 6542; there being, it would appear, more than one-third in number of the whole registered shipping of the country, consisting of vessels under fifty tons. Now, I may be in error in stating, that the average of this latter

class, (vessels under fifty tons,) as to the effect the new mode of measurement is to have upon it, has been taken from a single example. Some detail is gone into (vide pamphlet) to shew how the divisor has been obtained; and it is shewn how it is produced from the nine different classes of vessels into which the whole British shipping has been divided. With submission, I think that this divisor had much better have been fixed at any arbitrary rate, that would have produced a tonnage more like what the real burthen (or capacity rather) of a ship is, than the one adopted, (which makes the " Dunira," for instance, 1691 tons; yet, in capacity, to contain 156,248 solid feet; or, at 40 feet to the ton, 3906 tons;) yet, as the committee have affixed great importance to this point, and have affected to have deduced their divisor very exactly, so that the adoption of the new method "should not disturb the aggregate tonnage as before existing," we have a right to conclude that their measurements have been taken, so as at least to satisfy themselves, and in page 24 a list of ships is given, from which they profess to have attained the end they had in view. Being in possession of this list as a groundwork, they have produced in page 22 another table, in both of which the "Ann" appears as the sole representative of the smallest class, (of vessels under fifty tons.) The table at page 22 is intended to shew what will be the effect upon the whole nine classes of British ships; and as it is given in an answer, or in opposition, to a statement made by Mr. Steele, (a gentleman of Greenock, whose opinions the pamphlet in question seems to have been published to overthrow,) it is fairly to be considered as intended to carry the real belief of the committee, as to what this effect will be. Let us see what the result is, and how came it. They make out, from the actual measurement of a certain number of ships down to the sixth class, inclusive, that is to say, from 200 tons upwards, an increase of 2782 tons. The number of ships in each class measured is unquestionably too few, for the purpose of accuracy, but large ships so much resemble one another, that it is just possible that the above may be somewhere near the truth.

The next class, No. 7, 100 to 200 tons, seems to have been neutral, neither to have gained nor to have lost by the new measurement, therefore does not come into the account at all, (or, more properly speaking, they have omitted it altogether.) Then comes the vessels from 50 to 100 tons, class the 8th, which class, be it observed, contains no less than 5212 vessels, much above one-fourth of the whole registered ships of Britain, to obtain the average of which only five have been measured, and the result is, that in this class the decrease is 1381-8 tons. Next comes class 9, or vessels under fifty tons; and here, to obtain an average of 6542 vessels, stands the effect produced upon one! which is no less than eight tons decrease, and which produces a

reduction in the aggregate of the proportion taken of the whole class, 1217 tons. To understand the reference that is here made to the table framed by the committee, it must be understood that they have assumed such a number of vessels to each class, as the classes really bear to one another in the whole number of registered ships; thus taken, it becomes necessary, in order to preserve such relative proportions, to distribute the above measurements over 444 ships, producing an increase, as above stated, in the first six classes, of 2782 tons. Class 7 remains neutral, (or omitted rather;) those of the two last, or the least vessels, shewing together a decrease of 2599 tons; which results in a difference only of 183 tons, upon 444 vessels, or less than half a ton to each, from which the divisor is deducted, and which of course leaves the whole tonnage of the kingdom pretty much the same as it was. I will only further refer to the above table, to observe, that in taking the average of the smaller classes of vessels, it is quite evident that sufficient care has not been taken; the average size of vessels of the last class is probably not more than thirty-two tons to each, upon which tonnage it has been determined there is an error of eight tons, or 25 per cent., and this on the measurement of one! though any body who has observed the different sort of small vessels round the British coast, must have seen that their variety in construction is almost endless.

In respect to the effect the new tonnage bill is to have on different classes of shipping, I cannot but come to a conclusion directly contrary to the committee; that is to say, in the actual difference upon the whole, which I contend will be increased considerably, and that in every class: and this conclusion I come to from pretty general acquaintance with the shipping of the country, added to which, I think it may very naturally be concluded, that the consideration of saving the tonnage dues by reducing the nominal measurement, has actuated the builders and owners of small vessels, as well as those of the larger class; and this conclusion, I think, may be the more relied upon when it is considered, as the committee justly remark, that "the smaller class of vessels are oftener in and out of port;" and wherefore, I add, being more "sensitive" of the charges, their owners have naturally taken care to have reduced as much as possible.

Although I feel quite convinced that the above view will be found correct, yet we will suppose that it should be otherwise, and that the committee have estimated the effect as to measurement of the different classes correctly; there yet remains difficulties, inconsistencies, and objections, somewhat formidable. In the first place, the 3414 ships whose tonnage upon remeasurement would be increased, will very naturally remain as they are,-all those that would measure less, embracing 15,696 vessels, would most assuredly be new registered. Now, how is the great deside