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THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[March, 



GALVANIZED IRON. 



Aboi - t five years since a patent was taken out in this country, by M. Sorel, 

 for the purpose of galvanizing iron, by a process of ccating it with zinc, in a 

 similar manner to tinning, but for some cause, we believe a dispute among 

 certain capitalists, this patent has been allowed to remain in abeyance, during 

 which period, it has been in considerable use in Fiance, and is, at the pre- 

 sent time, we understand, extensively employed by the French government. 

 It is now taken up in this country by some spirited individuals, who have 

 established large works in London for zincing iron to any extent. The pro- 

 cess may be applied to both cast and wrought iron in any form. 



" The effect of zinc in protecting iron from oxidation," says Professor 

 Graham, " has been known to chemists for some time. When these two 

 metals are in contact, an electrical or galvanic relation is established between 

 them, by which the iron ceases to be susceptible of corrosion by dilute acids, 

 saline solution, or atmospheric humidity. It was found in experiments lately 

 conducted at Dublin and Liverpool, that small pieces of zinc attached to 

 each link of a chain-cable were adequate to defend it from corrosion in sea 

 water. The protection was observed to be complete even in the upper por- 

 tion of the iron chains by which buoys are moored (and which, from being 

 alternately exposed to sea water and air, is particularly liable to oxidation,) 

 so long as the zinc remained in contact with the iron links. The protecting 

 influence of the zinc could not be more certainly secured than in the articles 

 prepared by the patent process, the iron surface being uniformly coated over 

 by that metal. In trials to which I have had an opportunity of subjecting 

 them, the iron escaped untouched in acid liquids, so long as a particle of the 

 zinc covering remained undissolved. The same protection is afforded to iron 

 in the open atmosphere by zinc, with a loss of its own substance, which is 

 inappreciably minute. The zinc covering has the advantage over tinning, 

 that, although it may be worn off, and the iron below it partially exposed, i 

 the iron is still secured from oxidation by the galvanic action, while the 

 smallest quantity of zinc remains upon it ; whereas tin. in common tin plate, 

 affords no protection of this kind, and not being absolutely impermeable to 

 air and moisture, the iron under it soon begins to rust in a damp atmosphere. 

 The simplicity and perfect efficacy of the means employed to defend iron 

 from the wasting influence of air and humidity in this process of zinc tin- 

 ning, certainly entitle it to be ranked as one of the most valuable economical 

 discoveries of the present age." 



DRPAYERNE'S PATENT FOR PURIFYING AIR. 



An abstract of this patent appears in the Mechanics' Magazine; it is 

 granted to \Y. R. Vigers, Esq. of Russell-square, on behalf of Dr. Payerne, 

 " for a mode of keeping the air in confined places in a pure or respirable 

 state, to enable persons to remain or work under water and other places, 

 without a constant supply of fresh atmospheric air.'' 



The first thing claimed and specified is the depriving the atmosphere 

 in confined places of the carbonic acid gas which it contains, produced from 

 respiration or combustion, by means of quick lime and caustic alkali, or of 

 the lime alone, which is to be dissolved in eight times its weight of water. 

 The air in the apartment is to be passed through this caustic solution by a 

 pair of bellows, the nozzle of which reaches nearly to the bottom of the vessel 

 containing the lime and water. The vitiated air thus coming in contact with 

 the lime, the carbonic acid gas is absorbed. It is calculated that one cubic 

 foot of atmospheric air must be purified for each person per minute. 



2. The patentee claims the restoring the requisite quantity of oxygen, to 

 supply the place of that consumed ; which oxygen is to be procured from the 

 chloride of potash, or driven otf from the peroxide of manganese by means of 

 beat, into the apartment or allowed to escape from vessels into which it may 

 have been previously compressed. 



3. The patentee claims further, the purification of the air contained in the 

 diving bell, by the process described in claim 1, and the restoring the requi- 

 site proportion of oxygen from a vessel attached to the diving-bell, into which 

 the oxygen had been previously compressed ; also the allowing the escape of 

 atmospheric air, which had previously been compressed several atmospheres, 

 into two compartments, one of which is situated at each end of a diving bell, 

 somewhat resembling a boat inverted, the centre one being occupied by the 

 diver or workmen, who may, by means of stop-cocks, regulate the supply 

 according to their wants. 



The specification is of extraordinary length, filling no less than ten skins 

 of parchment, but the above extract contains all that is material in it. 



The bituminous pavement consists of blocks a foot square and 6 inches in 

 depth. These block are composed of an artificial bitumen and angular 

 broken stones, forming a concrete of considerable tenacity. When the 

 granite stones of the old pavement had been taken up and removed, a surface 

 with a considerable convexity in a transverse direction was prepared to re- 

 ceive the bituminous blocks. These are then laid down in straight lines 

 longitudinally, and breaking joint transversely. The blocks are not placed 

 close together, but with a space betwen them of about one inch all round 

 each block. This space is left for the purpose of being filled with melted 

 pitch in order to fix the blocks in their places. These spaces or joints be- 

 tween the blocks are filled in with pitch at several different times ; but when 

 the pitch joint is only 2 or 3 in. in depth, the blocks are quite immoveable. 

 When the first thickness of pitch has become quite solid, the joints are filled 

 with the same substance up to the top, and before the top surface of the 

 joint has time to set, a workman sprinkles it over with a sharp, yellow, large 

 grained sea sand, which sets firmly in the pitch. The pavement, when 

 finished, presents the appearance of an ordinary stone pavement, except that 

 the blocks, instead of ranging in straight lines transversely across the road, 

 are placed in straight lines in a longitudinal direction. We can see no good 

 reason for this deviation from the old practice, while on the other hand it has 

 obviously one great defect, namely, that the water falling on the surface is 

 checked in its escape to the sides at every course of stones, and thus the sur- 

 face of the roadway must be kept constantly wet. The unbroken transverse 

 lines of joints in an ordinary pavement, answer the useful purpose of minute 

 channels to convey the water off to the sides. It may be said that the bitu- 

 minous surface will prevent the penetration of water, and that the w ater lodg- 

 ing on the surface is of no consequence. We cannot agree in this, but con- 

 sider on the other hand that for this very reason bituminous pavement should 

 always lie laid with a slope in some direction, so that the water, which can 

 only otherwise escape by evaporating, may drain oft" it as fast as it falls. 



BITUMINOUS STREET PAVING. 



Notwithstanding several unsuccessful trials of bitumen in the paving of 

 carriage-ways, as in the Vauxhall Road some years ago, and more recently 

 in Oxford Street, the Parisian Bitumen Company is at this time engaged in 

 paving the square space opening into Hungerfor'd Market, at the bottom of 

 Hungerford Street, Strand. As this place is not subject to the same kind of 

 wear and tear as a street through which a rapid traffic is constantly passing, 

 it is possible that the bitumen may here answer better than in former trials. 

 and in any case it may interest our readers to know the method pursued bv 

 the Company in their present operations. 



MISCELLANEA. 



Stockton". — The bridge to substitute the Stockton Suspension Bridge is 

 now in progress ; two of the piers are completed — one on each side of the 

 stream; and the gangways and travelling cranes are erected. Mr. (. ra- 

 nt" Newcastle is the contractor for the masonry, and Mr. Kitchen of 

 Darlington, the contractor for the iron work. The foundation requires piles 

 50 feet long, and a 10-horse engine with a ram of 18 cwt., and three men to 

 drive them. The stone piers are dressed in rockwork, six feet broad at top ; 

 the span is 83 feet 6 inches between the piers ; the roadway is to be carried 

 by cast iron bearers about 3J feet deep. The site is about 100 feet above 

 the suspension bridge, up the stream or to the west of it. It is not certain 

 whether the suspension bridge will be taken down, or used as a turn. out for 

 wagons. 



Middlisborovgh Dock. — This dock was completed in the early part of 

 1842, and ships were admitted on the 12th of May in thai year, and the 

 shipment of coals has been carried on regularly in the dock since that time. 

 H lias an area of nine acres of water surface, and is entered by a commo- 

 dious channel rather more than a quarter of a mile in length, leading from 

 mid-channel of the river Tees. The entrance lock is 132 feet long, and 30 

 ; the depth on the sill averages about 18 feet at spring tides, and 

 15 feet at neap tides ; and the coping is 21 feet above the sill. The bottom 

 of the dock is three feet under the level of the sills; the sides of the dock 

 are sloped and paved with stones at the water's edge. For the shipment of 

 coal there are 10 staiths or "drops," at each of which coals may he loaded 

 at the rate of 5 keels, or 10 a tons per hour. Ballast is taken out at a very 

 low rate, by means ..f cranes situated at different places on the river hanks. 

 The branch railway leading from the Stockton and Darlington line, which 

 communicates with the dock, is situated on the south side of the town of 

 Middlesborough ; it terminates in 10 lines of double railway leading to the 10 

 drops. The raised platform is covered by three diverging lines of railway, it 

 comprises an area of la acres, and affords standage room for 1,200 loaded 

 wagons, or more than 3000 tons of coal, besides ready means of egress for 

 locomotives with their trains of empty wagons. Unfortunately the lock 

 entrance has been constructed too narrow for steam tugs to enter, of which 

 there are about 20 from 2j to 50 horse power. The channel from Middle 

 Tees is very much liable to silt up, and requires constant dredging. Mr. 

 Cubitt was the engineer, and Mr. Turnbull the resident engineer, and Mr. 

 Briggs the contractor. 



Lower Shannon Improvements. Ireland. — The works at Banagher 

 are contracted for by Mr. William M'Kenzie, and consist of deepening all the 

 fords in the river from Killalo to Athlone, either by dams and excavating, 

 or by dredging. Two 12 horse dredgers are employed, and two weirs are to 

 he constructed, 1100 feet long each, across the Shannon ; also a lock 170 

 feet by 40 feet, and 8 feet rise to pass an 80-horse steamer; likewise a stone 

 bridge at Banagher of 6 arches 60 feet span, and a 40 feet swivel bridge on 

 one side to pass the steamer through. The works are under government, 

 and are expected to be completed in the ensuing summer. 



The Oik: —A new seam vessel, o! 765 toi 



ihe 2Sth of January, having been built by Mr. Thomas K iyd :n 

 for the East India ami China irade. 



