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THE

MECHANICS' MAGAZINE,

MUSEUM,

Register, Journal,

AND

GAZETTE,

JANUARY 1st.--JUNE 25th, 1842.

VOL. XXXVI.

"To distinguish and present, as it were, in several columns, what is extant and already found, and what
is defective and farther to be provided."

BACON.

LONDON.

EDITED, PRINTED AND PUBLISHED, BY J. C. ROBERTSON,
MECHANICS' MAGAZINE OFFICE, 166, FLEET-STREET,

1842.

EDITED, PRINTED, AND PUBLISHED BY J. C. ROBERTSON, 166, FLEET STREET.

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Mechanics' Magazine,

MUSEUM, REGISTER, JOURNAL, AND GAZETTE.

SATURDAY, JANUARY 1, 1842.

No. 960.]

[Price 3d.

Edited, Printed and Pablished by J. C. Robertson, No. 166, Fleet-street.

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MR. GIBBS'S IMPROVED SYSTEM OF BRIDGE BUILding.

We have already given a brief notice (No. 958, p. 490) of this system of bridge building, in our abstract of Mr. Gibbs's specification of certain patented improvements in roads, railways, &c., among which that system is included; but justice to the skill and ingenuity by which it is distinguished, and the many important advantages which it offers, requires that we should lay a more detailed and fuller account of it before our readers.

The master feature of this system is, that it combines in one, the best properties both of the common arc bridge, and the suspension bridge, without the worst of their respective drawbacks-the solidity and strength of the former without its abutments, and the lightness of the latter without its land ties. If there be no fallacy in the principles of construction followed by Mr. Gibbs-and for ourselves we do not see any-it should follow, that if care be taken in adjusting the weight of the materials employed, a bridge built on this system will be so perfectly equilibrated, as to rest perpendicularly on its piers without any out-thrust what

ever.

The engravings on our front page exhibits an elevation and plan of an entire bridge constructed on this plan. following description of the details we extract from Mr. Gibbs's specification.

The

"AA are the piers; B B the arches, which may be made of hollow iron tubes or of solid timber; C C are the suspending or main chains, or inverted arch; D D is the roadway, which may be fixed to the suspending rods; E E, rods which connect the two arches together; F F are what I call thrusting braces, which commence at the lower part of each pier, and are united to the first series of suspending rods at the junction of the inverted arch C C. Another series of braces G G, called the suspending braces, commence at the top of each pier at the place where the arches C C, on each side of the pier are connected together. These braces are connected with the suspending rods E E, at their junction with the lower arch B B. After the first set of tions of the arches are combined together, a second set can be added, precisely on the same principle as before described, each end of the bridge terminating with a half arch, and counterbalanced and resting upon the piers H H. It will be obvious, however, that the succeeding portions of the arches as

por

they recede from the pier will have to sustain less weight than those nearer to the pier, and may accordingly be made lighter, commensurately with the load they will have to sustain. As many of these arches as may be required to form the width of the bridge, may be connected together by suitable horizontal and diagonal rods and braces. In some cases it may be of advantage to run the two arches through each other, which will permit a greater curvature to be given to the arches.

"The proportions of the different parts of the weights and nature of the materials to be used, and the mode of combinating them together at the joints will vary according to the character of the structure, and must be left to the judgment and skill of the engineer employed in each case."

PRACTICAL SUGGESTIONS FOR THE PRO-
TECTION OF MANUFACTORIES FROM
FIRE.

Sir,-Although I am very reluctant to obtrude my opinions on public notice, yet feeling most strongly the importance of the subject, and possessing the means, from experience, of affording information that may prove beneficial, I will hesitate no longer to offer, through the medium of your valuable columns, an explanation of the means I have long since adopted, with great advantage, to secure my premises and property from the calamity of fire. The frequent and awful conflagrations which have lately taken place, to the great injury both of public and private property, render it extremely desirable that some means should be taken to prevent a recurrence of them, if possible; and as the precautions about to be suggested have been attended with most beneficial results in my own establishment, I deem it proper persuaded that many or most of the reto make them generally known, as I feel cent fires might have been arrested, if similar care had been taken.

I am the proprietor of an establishment where a number of workmen are employed amongst timber, shavings, linen, tow, oils, and where various articles of a combustible nature are used. To prevent an accident by fire, I have established several precautions. One of these is, that under each work-bench,

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