and adopted in the French service. The drawing (see plate, fig. 4) I have taken from St. Remy, a most valuable authority for his period, about the year 1702. In this work the lock is described as the fusil-musket lock, because the flint was first applied to fusils; it was afterwards applied to the musket. In the Musée d'Artillerie at Paris, they describe the lock thus: "Fusil mousquet de Vauban qui au mécanisme ordinaire de ....

I

I

a batterie reunit

le serpentin pour la mèche. A la bataille de Steinkerque (1692) les François jetèrent spontanément leurs mousquets, pour se servir des fusils pris aux ennemis. Ce fut alors que Vauban imagina son fusil mousquet, dans lequel la mèche sert au defaut de la batterie." The flint had not gained much ground in France at this period, although in the Spanish army it had been long used and known as the Platine à Miquelet. may mention that a photograph of the Vauban lock has been kindly sent to me by the Minister of War in Paris,—an attention which I esteem highly. Without paying too much attention to the affairs of our Gallic neighbours, may mention that from 1693 to 1714, a series of experiments with flintlocks was being carried on in France. In 1703 many flint-locks were in service, and the exquisite specimen dated 1705, made from designs by La Collombe, (see plate, fig. 6,) in my own possession, shows that in Paris they were no mean proficients in flint-locks; yet no model was adopted in the French service until 1714. From that time the French Government has made a complete series of model arms and their transformations up to the present date. In Queen Anne's reign a change took place in flint-locks so as to strengthen their form of construction; it was to carry the pan further through, so that the hammer-pin might be better supported. From this time up to 1837 no change took place. About 1772 Thomas Wright and C. Byrne produced a flint-lock which was self-priming, and self-hammerclosed; the patent can be seen by referring to No. 1,003 in the Collections of Patents on Locks. Cock-and-hen locks are alluded to in the patent Nov. 28th, A.D. 1799. Flint-locks are mentioned as being made so that the flint, by the operation of cocking, presents a different angle to the hen or hammer every time the piece is fired.

The very name of PERCUSSION Seems so identified with our own day, that in fact it is almost too well known to require explanation. Cock your gun, cap, and fire, explains all; a few words as to the origin of the principle are, however, desirable. For its invention, like that of gunpowder, we are indebted to an ecclesiastic, viz. to Schwartz, the monk, for the latter, and to the Rev. A. J. Forsyth for the former. In 1807 Forsyth took out a patent to explode the charge by a grain of detonating powder. In 1816 Joseph Manton took out a patent for tube guns, which are still used; and in 1821 Samson Davis took out another for using the same lock, either on the percussion principle or with gunpowder, without changing the cock or hammer. The original of this patent may be seen in the collection in the Museum, and I regret that, as a left-hand lock is there, I have not been able to obtain a right-hand one as a fellow, in order to complete the pair.*

It was not until 1837 that the percussion principle assumed such a form as to be worthy of adoption in Her Majesty's Service. At first some * A right-hand lock has since been placed in the Collection. (See plate, fig. 7.)

special arms were got up for the Foot Guards, with back-action locks, at the same time that some old arms were altered from flint to percussion. These being found satisfactory were continued in use for some time. A back-action carbine, known as the Victoria Carbine, the same as that now carried by the Horse Guards, was also adopted at that time. But, although the percussion principle was adopted in certain corps, and in the Brunswick Rifle for the Rifle Brigade, yet not until 1842 was a percussion model decided upon for the Army, or rather for the Line. This arm had not a back but a bar action. This remained the weapon of the Line and East India Company's Army until 1853. One great defect stamped the Line lock of 1842, viz. the shortness of the mainspring, which produced a very cramped action. There was also the radical fault of a hook-mainspring instead of a swivel. When the wheel-lock fell into disuse, the swivel that used to connect the mainspring with the tumbler was forgotten and ignored. So great is the difference of action between a swivel and hook-mainspring, that the former may be put together dry, and it will work easily and smoothly, whilst the hook-mainspring, unless put together with oil, will immediately grind; and so in fact it will always, unless kept constantly lubricated.

We have now reached a period when the experience of centuries has produced a satisfactory result in the lock of 1853, the pattern lock of our Service, which in simplicity deserves our praise, and in production our wonder. It will be superfluous to take up your time in detailing the processes of manufacture. I will only draw your attention to that most interesting collection in the Enfield rifle room in this Institution, where you may trace the gradual production of the different limbs and pieces from the raw material up to the highly-finished and perfect lock. The stages of fabrication, though numerous, are very interesting and very instructive.

Friday, May 20th, 1859.

Colonel the Hon. JAMES LINDSAY in the Chair.

ON ROTATORY MOTION APPLIED TO OBTAIN STABILITY FOR ASTRONOMICAL OBSERVATIONS AT SEA.

By the Rev. BADEN POWELL, M.A. F.R.S., &c. Savilian Professor of Geometry in the University of Oxford.

ABSTRACT.

THE subject of rotatory motion is one of large extent when considered in reference to the principles of theoretical mechanics, and is connected with some of the most abstruse theories of analytical dynamics. Yet some of its simpler properties, laws, and results admit of direct experimental demonstration, and such elementary ideas of the subject as can be thus communicated are fortunately quite sufficient for the full comprehension and elucidation of some of the most important and valuable practical applications of the principle.

The object of the present Lecture is restricted to the explanation of one or two of such applications which are interesting, and promise to be of considerable practical importance to nautical astronomy in supplying the means for attaining that much-desired object, a stable support applicable to the purposes of astronomical observations on board ship.

In order to render the description of such inventions intelligible, it will be necessary first to advert to one or two theoretical points involved in the nature of the constructions.

The principle of "the composition of rotatory motion" is one of fundamental importance for the explanation of nearly all phenomena of the kind we are considering. It is susceptible of very simple and elementary illustration. If we merely consider the familiar case of composition of rectilinear motions, a body moving by a force which would alone carry it through a given space in a given time, acted upon also by another force, which in the same time alone would carry it through a space in a direction transverse to the former, will, under both, in the same time, describe a space which is the diagonal of the parallelogram of which the two former are the sides.

In like manner, if a body be rotating about an axis, a point in its circumference describes in a small interval of time a small arc, which may be regarded as rectilinear; if a force act on it which in the same time would cause it to rotate in another direction, or to describe a small arc transverse to the first direction, it will, under both, describe the diagonal of the small parallelogram.

In order that the small arc of the circumference may take this new position, it is merely necessary that the axis should take a new direction,

or the plane of rotation of the whole body should shift into a new position, without any change in its inclination to a given fixed plane.

This is the actual case of the earth's rotation as affected by the attractive force of the sun and moon tending to pull down the protuberant equatoreal matter of the terrestrial spheroid into the fixed plane of the ecliptic or earth's orbit, giving rise to that slow shifting of the direction of the earth's axis, which carries with it the equinoctial points or intersections of the equator with the ecliptic, without the smallest change in the inclination of the one to the other, and which is the explanation of the wellknown phenomenon, the precession of equinoxes.

Hence, in the general case of compounded rotatory motions the resulting effect of this kind is called a "precessional motion." Of this we have many practical instances, especially in the constructions about to be described.

It is also necessary to explain the term "axes of rotation." If any body of whatever form be forcibly struck, it will acquire, besides the general motion of translation, a rotatory motion, unless the stroke happen to be directed exactly through its centre of gravity. There is always some one line passing through it, about which it will for the moment be rotating as an axis; but in general this direction will be perpetually changing, until the rotation at length becomes permanently settled about some line related to the figure of the whole mass, which is termed one of its "principal axes." It can be demonstrated that every body has at least three such axes, and in regular figures their position can be determined.

The principle termed "the constancy of the plane of rotation" is evinced in this, that a heavy body rotating about its principal axis shows. a powerful tendency to continue its rotation about that axis, in the plane in which it was originally impressed, so much so as to offer a very forcible resistance to any attempt to give it while rotating any inclination out of that plane. This is most conspicuously displayed when the rotating body is mounted on gymbals, so as to be free to turn in any direction.

To occasion this tendency there is, besides the mere inertia, the law of permanent rotation about a principal axis, and the composition of rotations, from which any small tendency to change of direction would not show itself directly, being compounded with the original rotatory force.

These, and a variety of other analogous and related phenomena, are conveniently exhibited by the small apparatus now generally known under the name of the "Gyroscope," originally devised by Bohnenberger, and described by him in 1816, and since largely improved upon by various other mechanists, until it has received its most complete form from the improvements of Professor Wheatstone, in 1854. While for more specific purposes it has received a different construction in the beautiful adaptation of M. Foucault, in 1854: the idea of which was, however, suggested by Mr. Sang of Edinburgh so long ago as 1836.

These preliminary considerations will prepare the way for the elucidation of that remarkable practical application of the principle of rotatory stability which is the specific object of the present Lecture, the means of affording a stable platform for astronomical observations on board ship, exempt from the motion of the vessel.

It is true that for some of the most ordinary, and at the same time most important, operations of nautical astronomy, this stability, owing to the happy invention of Hadley, is not needed.

But there are other classes of observations which it is highly desirable, if not necessary, to make at sea, for which this principle of stability is absolutely essential. Nay, even for the ordinary purpose of measuring altitudes, there are continually occurring cases when the sea-horizon cannot be discerned, while the sun or star is clearly seen above. Hence some means of obtaining an artificial horizontal level becomes of great importance, but unattainable by those means so easily practised on land, by reason of the motion of the ship. Hence, with only this limited, but important, object in view, various plans have been devised; and of these one of the most hopeful was derived from the principle of rotatory stability. The commonest observation showed how easily such stability (in a general sense) was acquired by the mere spinning of a top: and, though many other considerations were really involved, not at first fully apprehended, yet the general idea seems to have presented itself more than a century ago to the inventive mind of Mr. Serson; at least, as far as seems at present known, this is the earliest attempt of the kind on record. The invention consisted essentially in a circular plane reflector through the centre of which an axis passed, the lower part of which terminated in a steel point resting in a hemispherical cup of agate: on the upper a string could be wound by which it was spun; as the support moved with the ship the point shifted its position in the cup, always tending to the lowest point, and thus a nearly horizontal rotation was attained. A brass rim round the reflector descended so low as to bring the centre of gravity of the whole nearly into coincidence with the point of support. If this coincidence had been exact, the instrument would have been more perfect, theoretically, than some since made.

An account of the instrument will be found in Brewster's Cyclopædia, art. Sextant, with a figure. A shorter account is given in Rees's Cyclopædia, art. Horizontal Speculum.

The inventor went on board the Victory in 1744 to try the plan. In this ship (of 110 guns and 1100 men) he was unfortunately lost, when it was totally wrecked by striking on a reef off Alderney in the night.

In the Phil. Trans. 1751-2, there is a paper by Mr. James Short, who speaks of the invention as well known. He also states that this top when spun took "the true horizontal plane," and was not disturbed by any motion or inclination given to the box in which it is placed; and thus "may be proper to be used aboard ship" for taking altitudes.

Mr. Short's object was to try whether (as had been suggested) the air had any share in causing this horizontality. He therefore tried spinning it in vacuo; and observed that, while in air it kept up 36 minutes, in vacuo it continued spinning for 2 hours 16 minutes, "preserving a perfect horizontality for three quarters of an hour."

Owing to whatever cause, however, the invention of Serson seems to have fallen not only into disuse but into oblivion. Some plans on exactly the same principle have been proposed more recently, apparently without any knowledge on the part of their inventors of Serson's priority. But it does not appear that any material improvement in the performance has been attained.