238

THE NEW LONDON BRIDGE,

Sir,-After the New London Bridge was begun, a hint was given to widen it, the breadth assigned to it in the original plan being thought too narrow for the increasing population. It has, accordingly, been since widened; and so far so good. There was a readiness shown, in this instance, to benefit by anything in the way of friendly suggestion, which emboldens me to anticipate for the following additional hint an equally favourable reception.

It seems to be the present intention to make the top side walls of the bridge blank stone walls, such as bridges in former days used to be furnished with, only somewhat higher. Apparently, they will not be quite so bigh as to make a close lane or alley of the bridge, but they will be so high that nobody except persons of gigantic stature will have more than a tiptoe view up or down the river. Now, can anything, I would ask, be more unsightly, more inconvenient, more objectionable? There can be but one reason, I should think, of any consequence, for adopting this mode of finishing, in preference to an open balustra ding,-namely, that the curious and idle may be prevented from loitering to gaze through at objects on the water, and thereby obstructing the stream of passengers, But let us consider, on the other hand, that the bridge will, for want of an open balustrade, be deprived of one of the greatest ornaments to such structures; that the footway must, for want of air and sun, be in a continually dirty and greasy state; that

In the "Mechanics' Magazine," by the author, we believe, of the present communication.-ED.

in the winter, the snow must, for want of a passage, collect in drifts under the dead walls, as in a lane or hollow way; and that in the summer, the dust will gather in the same way, and, whenever the wind is high, be raised in whirlwinds, to the extreme annoyance of passen. gers. Nor will these be the only evils attending this mode of construction. The sun's rays, in hot weather, will reflect so strongly from the glass-like granite walls, as to make the footway almost insufferable. Again; in stormy weather, your head must receive all that comes, except what passes through the arches. How basket people or porters will be able to stem it along, I know not; as to the public in general, they will meet with many an everlasting remembrance, in stiff necks, jaws-ache, ear-ache, tooth ache, &c. And, after all, can you stop curiosity? I say, you may as well attempt to stop the general tide. With these dead walls, about breast or shoulder high, the people will at least have a peep over; objects on the water will be seen at a distance; and whenever there is anything to draw attention particularly, up will jump nimble Jack and Sall, kicking their horse. shoe heels in the faces of the passers by. Besides, I will take upon me to say, three-fourths of the people's curiosity will be done away with when the old bridge is removed, as there will be then no water-fall to marvel at. There is yet another objection to this blank wall,-an important one too, though, perchance, it may be laughed at. The power of a westerly wind on the Thames is sometimes tremendous; and this bridge stands well for a broadside. With such a wind, hemmed in between the houses, warehouses, steeples, &c., I should not be at all surprised to see this wall laid flat, or burled amongst the shipping (an awkward cargo ratber). As strange things have happened before, and may happen again. I once, some thirty years ago, saw a thing in Park Lane, which astonished every beholder. It was a wall two bricks thick, covered with a six inch coping,

Yours, &c.

6, East Place, Lambeth, May 5, 1829.

T.

SPITALFIELDS MECHANICS'

INSTITUTION.

We are happy to learn, that though the prevalent distress in the neighbourhood of Spitalfields necessarily occasions the number of members for whose benefit this Institution was established, to be limited, yet that the present number is sufficient for the support of the Institution (the expenditure of which is very moderate), and that the esta blishment is, upon the whole, in a prosperous condition. During the last year, about thirty pounds have been paid in liquidation of outstanding debts (to the amount of fifty pounds), in addition to the current expenses of the establishment. The improvement in the financial affairs of the Society is attributable to the lectures delivered by Messrs. Hemming, Preston, Williams, Dr. Mitchell, and other gentlemen, gratui tously; to the honorary services of Mr. Beck, the Secretary; and to a donation of ten pounds, by Thomas Gibson, Esq., President. The library is scarcely inferior to that of the London Mechanies' Institution, and the philosophical apparatus is splendid and complete. Lectures are delivered once a week; and the reading-rooms, which are supplied with the popular periodicals and daily papers, are open every evening. The Society is held at No. 4, Wood-street, Spitalfields. At the Quarterly Meeting, on the 30th of April last, thanks were voted to the Donors, Lecturers, and Honorary Secretary (who was elected Hondrary Member, for his services), and to Mr. Hemming, the Chairman. The fourth Anniversary was cele

289

brated on Thursday, April 23, by a supper, at which about forty members attended, and the evening was spent with much harmony and con⚫ viviality.

WOOD ENGRAVING,

We had the pleasure of being present at an extremely entertaining and instructive lesture on this subject, delivered on Friday evening last, to a very numerous and respectable audience, at the Royal Institution, by Mr. A. J. Mason, woodengraver. The lecturer considered the origin of this art to be contemporaneous with that of printing itself-as, in fact, identified with itthe first essays in printing having consisted of impressions of letters engraved in relief on wooden blocks. The cutting out of pictorial embellishments, as well as letters, in wood, was but an extension of the same species of art. While books continued to be printed from blocks only, the art of wood engraving made great progress; in evidence of which Mr. Mason exhibited some very remarkable specimens, with the loan of which, for the occasion, he had been obligingly favoured by that distinguished patron of the arts, Earl Spencer. The specimens con. sisted not only of impressions from wooden blocks, but of the original blocks themselves. After printing with moveable types was intro. duced, the art of wood engraving, both as regarded letters and pic. tures, fell rapidly into disuse, and, for more than a century, it may be said to have been altogether lost sight of. When it was at length revived by the celebrated Bewick, in England, the first wood engraving he produced was of an exceedingly rude character, and not at all to be compared with the specimens still extant of the old block-book times. Yet of such importance was the re vival, in any shape, of the art considered to be, that Bewick was rewarded for this his first attempt, by a premium from the Society of Arts. With the progress which the art has subsequently made, in the hands of

1

242

bar E, and then screwed by the thumb-screw h.

PD moves freely in a circular groove on the end of the bar E, having G, the vertex of the intended curve, for its centre.

d is a slit socket, traversing the whole length of A; on a projecting part of which is fixed a tube T, to receive a pen or tracer. On this tube moves a socket, to which is screwed the rod C; so that, when the axis of P D, C and E, are in the same vertical plane, the centre of the tube T will coincide with G.

M is a bridge, fastened by the screws n n to a slit socket, moveable on the rod B; and at right angles to the bridge is another socket t, through which, for greater steadiness, slides the long socket b, screwed tot by the milled thumb-screw o.

The bar P D moves between the socket below M, and that of t, and is prevented from any lateral shake, by a pin in the under side of the bridge M traversing in the groove e.

Now, from these combinations it is evident, that if the handle T be moved either to the right or left, the rod C will always preserve its parallelism to the fixed axis of E, and the tracing point at T will generate a portion of the parabolic curve HG N.

If the bar P D remain stationary, and that of E be moved, then will the tracer at T describe a right line.

REPLY OF MR. CHILD TO

MR. IBBETSON.

Sir, It was not my intention to request that the pages of the "Mechanics' Magazine" should be occupied by any further observations respecting my youthful amusements; but as I think the communications inserted in No. 291 require some notice, I shall be much obliged by an insertion of the following remarks, at your earliest convenience.

The two specimens engraved and published are not such as I should have selected for setting "the only point" at rest; indeed, the second figure has no reference to the observations of Mr. Ibbetson, and the other is, probably, the first I ever drew of the kind. Therefore, I

wish to say, that nearly half a century ago, it was no secret with me to move a pin along the radius of a wheel, fix it at any point therein, and then cause it to work a lever backwards and forwards, by playing in a straight groove made in a direction passing through the centre of motion of the said lever. This lever I applied to more purposes than one. I made various other combinations of wheels and levers, and of wheels of different forms,-such as ellipses, ovals, &c., and also of segments of circles and ellipses, the parabola, &c. These I still have; and of these, combined in a variety of ways, my apparatus consists. I have never made a secret of these things; numbers of persons saw them when newly made, and many gentlemen, amateur mechanics, from distant places, have lately seen them,-not at a distance, but so as to examine them minutely, and enter into the rationale of many of their operations, which are, in their opinion, entirely new: they had ocular demonstration "that the means" had existed" of graduating an ellipsis, and of cutting elliptical wheels into any number* of teeth," and of their "use in the arts,”—at least, in the art of describing figures. When I had produced a figure, by a combination of wheels, &c. moving a surface against a fixed point, and wished to describe the same figure on a fixed surface, by a moving point, I had to reverse the arrangement of such combination, and apply it to the point, instead of apply. ing it to the surface. This being the case, I still say the "chuck is on the same principle;" and this fact Mr. I. should know now, as well as I did then; if he does not, this communication will furnish a hint for the producing of new figures.

Permit me here, Mr. Editor, to refer your readers to the following remark, made by Mr. Ibbetson, vol. vi. p. 552:-"I constructed an instrument on the principle of the

Although elliptical, &c. wheels can be cut into any number of teeth, yet they will work only with peculiar numbers, adapted to the figure of the wheels.