1840,] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAC. 



178 



a pressure on the periphery of a wheel, fixed on an axle and kept 'rotating, 

 would produce the same results which were admitted to exist in practice. 



The paper read was a " Descrijition of a Lift Bridge, erected over the 

 Grand Surrey Canal, on the line of the Thames Junction Bratwh of the 

 London, Brighton, and South Coast Railway." By Mr. R. J. Hood, 

 M. Inst. C. E. 



The act fnrthe construction of this hranch, which was a single line, one 

 mile in length, provided that the crossing of the Grand Surrey Canal should 

 be by a swing hridge; but as there were many obstacles in the way of this 

 clause being carried out, and as it was not thought to be the most conve- 

 nient form of construction, it was determined, after due consideration of the 

 advantages and disadvantages of each particular kind of moveable bridge, to 

 erect one on a principle which might he designated a " lift bridge." This 

 consisted, simply, of a rectangular platform, 23J- feet in width, and 35 feet 

 in length, carrying on one side a line of rails, and on the other side a road- 

 way for carts; it was formed of four beams of oak timber, undertrussed 

 with wrought-iron rods and cast-iron saddles, those for carrying the rails 

 (which were bridge-shaped), being stronger than the others, and having a 

 flooring of S-inch planking ; the platform rested, when down, upon piles 

 driven into a bed of hard gravel, met with at a depth of about 20 feet below 

 the water line. The platform, which was abont 12J tons in weight, was 

 suspended at the four corners by galvanised wire ropes, four inches in cir- 

 cumference, attached to the end of each oak transome, by means of strong 

 bow springs, and passing over pulleys fixed on four pairs of cast-iron 

 standards, also supported on piles, and fastened at the other end to drums, 

 3 feet in diameter, each pair of which were keyed on to the same hori- 

 zontal shaft, situated a few inches under the rail and road level. Upon the 

 same sliafts there were also fixed six other drums, of a like diameter with 

 the former, carrying, upon coils of wire rope, 2| inches in circumference, 

 balance weights, of a total weight of 125 Wis, but not equally distributed, 

 intended to assist in raising the platform, and which descended in cast-iron 

 cylinders, or wells. Motion was given to one end of each shaft, by means 

 of simple hand-gearing, consisting of a train of wheelsand pinions, by which 

 the power was multiplied twenty-six times. 



The level of the rails, above the water-line, was 4.V feet, and as the plat- 

 form was capable of being raised 9J feet, sufficient room was atforded for 

 the passage of the barges, the greatest number of which ever passing 

 through in the twenty-four hours being fifteen, and since the erection of the 

 bridge, not one in a hundred had been detained one minute; though on 

 this point, as well as on many others, the Canal Company had raised factious 

 objections, owing to which, and to the design having to be submitted for 

 approval to the Railway Board, great delay arose in the commencement, and 

 also in the execution of the work, augmenling the actual cost to 1,300/., 

 which was beyond what, it was presumed, a similar work could, under more 

 favourable circumstances, and when the construction was not novel, be 

 executed for. 



The bridge was stated to have proved very successful, and in situations 

 where only a given headway was required for a limited span, this kind of 

 construction was recommended. 



April 9. — The paper read was " On the Construction of Locks and Keys.'' 

 By Mr. J. Chubb, Assoc. Inst. C. E. 



The author commenced by stating, that the most ancient lock, of whose 

 form and construction there was any certain knowledge, was the Egyptian, 

 which had been in use for upwards of four thousand years. The construc- 

 tion of this lock was minutely described, also that of the ancient "warded" 

 and "letter" locks, and considerable antiquarian research was displayed in 

 tracing their origin and introduction. These three kinds of locks were, in 

 principle, the foundation of all modern locks, which might be thus enume- 

 rated, reversed, for obvious reasons, in their order of antiquity: — 



First, — The letter locks; mostly used for padlocks, and were so far con- 

 venient, as a key was not required for opening them. A modification of 

 this lock had been proposed, called the "scutcheon" lock, for securing 

 doors and iron safes, but it was too expensive and complicated to come into 

 general use. 



Second, — Locks having fixed wards, in which no real improvement had 

 been made in modern times. These locks were bad in principle, as they 

 conld be easily picked; and owing to many thousands of them being yearly 

 made, that could be passed by the same key, little or no security was 

 afforded by them; in fact, it might be safely asserted, that twenty skeleton 

 keys would open all the locks, of a given size, made upon this prmciple. 



Third, — The Egyptian lock; the essential principle of which was, that of 

 moveable pins, or studs dropping into, and securing the bolt, all of which 

 must be raised to the proper height, by corresponding pins in the end of 

 the key, before the bolt could be unfastened. This lock was the foundation 

 upon which most of the ingenious inventions of late years had been based, 

 ditFering only in the forms of the moveable obstructions to the bolt — some 

 of which acted vertically, others horizontally, some with a rotatory motion, 

 and many others in an endless variety of ways; but of all these it was 

 thought sutEcient to describe only those best known and appreciated — 

 namely, Barron's, Bramah's, and Chubb's. 



In Barron's lock, patented in 1774, a great improvement was made upon 

 the ancient Egyptian, by the introduction of the over-lift, wards being also 

 used; but, from the fact of there being only two tumblers, it was evident 

 that no great change or permutation could be made in the combinations. 



In Bramah's lock, patented in the year 1784, there was a compound of 

 both direct and rotatory motion given to the key, instead of simply the 

 latter, as in Barron's lock. It consisted of a number of sliders, having 

 notches of various depths cut on one edge, so that the motion of ihe bolt 

 was totally prevented, until each slider was pressed down to its exact depth, 

 which was effected by the key having six cuts in it of different lengths. 



In Chubb's lock, first patented in 1818, and since modified and improved 

 bv various subsequent patents, there were six separate and distinct tumblers, 

 placed over each other, and capable of being elevated to different heights, 

 but all moving on the centre pin. This lock differed from the others, in 

 having a " detector," by which any attempt to pick, or open the lock with 

 a false key, was immediately notified on the nest application of its own key. 



Calculations were then gone into, to show the number of different com- 

 binations which might be made in this lock; and it appeared, that with an 

 average-sized key, having six steps, each capable of being reduced in height 

 twenty times, the number of changes would be 86,400; that if the seventh 

 step, which threw the bolt, was taken into account, the reduction of it only 

 ten times would increase the number to 864,000. Further, that as the 

 drill-pins of the locks, and the pipes of the keys, might be made of three 

 different sizes, the total number of changes would he 2,592,000. In keys 

 of the smallest size, the total number would be 648,000, whilst in those of 

 the largest size it would be increased to 7,776,000 changes. 



In conclusion, it was stated, that the manufacture of locks and keys was 

 principally carried on at Wolverhampton and the adjacent towns, Birming- 

 ham, and London, and that the fundamental principle upon which all locks 

 should be made, were perfect security — strength, so as to resist attempts to 

 force them, or of opening by picklocks and false keys — simplicity in the 

 arrangement, so that any stranger, having the proper key, might be able to 

 open the lock — and durability. 



The paper was illustrated by a series of diagrams, and a variety of speci- 

 mens of the locks and keys noticed in the paper; and also by a number of 

 Gothic locks and keys of very elaborate workmanship, suitable for eccle- 

 siastical buildings, &c., from Mr. Chubb's works, in London. 



In the discussion which ensued many additions were made to the histori- 

 cal part of the subject, and various ingenious contrivances were described, 

 which had been successfully applied, to give increased security to locks of 

 ordinary construction. The combinations in the locks of Summerford, and 

 McKinnon (of New York), were also fully described; an advantage being 

 claimed for the former, in making one tumbler to lift and the other to fall, 

 in order to open it; and, for the latter, that, by the addition of a curtain, of 

 case-hardened iron, three-quarters of an inch in thickness, radiating from 

 the centre of the pin, and a radiating key, there were no means of reaching 

 the tumblers, for the purpose of taking an impression, or otherwise, except 

 by cutting through that curtain. On the other hand, it was positively 

 asserted, that no impression could be taken of, or means invented for picking, 

 a lock which had six tumblers, although it could be easily done with locks 

 having fixed wards; further, that Chubb's lock was a decided improvement 

 on all others of the same character, inasmuch as it possessed a " detector," 

 which formed really the peculiar feature of that lock; the excellence of the 

 workmanship tended also to the facility of action and consequent durability, 

 for which it was so celebrated. 



April 16. — The discussion upon Mr. Chubb's paper, "On ihe Construction 

 of Locks and Keys," was renewed, and extended to such a length as to 

 preclude the reading of any paper. 



Several locks which had not been previously mentioned, were exhibited, 

 and their peculiarities of construction were described. These bore the 

 names of their inventors — Davis, Parsons, Williams, and Nettlefold. 



It was urged, that the curtain which had been mentioned might be essen- 

 tial for Snmraerford's lock, but could not be, in any degree, useful in Chubb's 

 lock; in fact, that its only effect would be to induce complication, and aug- 

 ment the cost, without increasing the security. 



Among numerous instances of ingenious devices for opening locks, that 

 stated to have been tried in America excited much attention. The process 

 was described to be, that the operator, after inserting two pieces of India 

 rubber, to limit the sphere of action, injected from a force-pump a com- 

 position of glue and molasses, in a heated state, which chilled quickly, and, 

 although extremely elastic, had the property of retaining the form and 

 position of the loner side, or bellies of the tumblers, and that after being 

 cut out of the lock, by a thin-bladed instrument, a key could be made from 

 the impression. 



In explanation of this, however, it was shown, that in Chubb's lock there 

 existed no similarity between the position of the beUies of the tumblers, 

 when at rest, and the figure of the bit of the key; and, therefore, that even 

 supposing it to be possible to obtain an accurate impression of the position 

 of the bellies of the tumblers, when at rest, no indication would be afforded 

 of the combination, or any assistance be given for making a false key. In 

 further confirmation of this, a lock by Chubb was shown, in which, when 

 at rest, the bellies of the tumblers were perfectly uniform, and in the same 

 plane, so that an impression of the inside of such a lock must be utterly 

 useless for any purpose. 



Although it had been asserted that Chubb's locks had been picked, it was 

 admitted that it had never been proved that those locks had really been made 

 by the inventor; but, on the other hand, it had frequently been shown that 

 purious imitations of the first expired patent had been sold in large quan- 



