2S4 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[August, 



parent at the upper ends of the pools, where the heavy materials, such 

 as gravel and boulders, were first deposited on coming in contact with 

 the comparatively still water |)roduced by the weirs, and as the stream 

 advanced, by deposit of the sand and lighter materials further down. 

 At first recourse was had to remedy the evil by raising the weirs by 

 means of boards, which were frequently washed away by the floods, 

 and had to be renewed as the water subsided, and partly by raking 

 the gravel and sand to the sides of the river. But as soon as the 

 power of the dredging engine became known, recourse was had to it; 

 it was, however, still found that although they had procured and kept 

 in constant work two of these engines, the deposit was gaining on 

 them ; they therefore had recourse to the adoption of canals, as before 

 stated, commencing w ith those parts which were the most affected by 

 the deposit, until they now use only a little more than four miles out 

 of a distance of twenty-two miles of the river. The Aire and Calder 

 Company now use about nineteen miles out of forty-three, by having 

 recourse to dredging, and raising their weirs by means of boards, as 

 before described. That they, are enabled at present to navigate a 

 greater proportion of the rivers than their neighbours, no doubt 

 arises principally from the «ircumstance of their being situated further 

 pown the stream, and their being numerous weirs above, which retain 

 the sand and gravel from coming down to them. 



I cannot conclude these remarks better than by giving the result of 

 my observation and experience, which i« that converting natural rivers 

 into artificial navigations by erecting dams across them, is much to be 

 deprecated. First, because the dams cause the adjoining lands to be 

 more frequently overflowed than they otherwise would be. Secondly, 

 because dams obstruct the ordinary drainage of the country. Thirdly, 

 because the object sought is but imperfectly obtained, and lastly, 

 because it is the means of materially retarding, if not of entirely pre- 

 venting, the adoption of the more efficient means of providing for 

 inland navigation by artificial canals, which, if made at all, are rarely 

 or never made so complete as they would have been had no attempt 

 been made to adapt the natural rivers. 



PROCEEDINGS OF SCIENTIFIC SOCIETIES. 



INSTITUTION OF CIVIL ENGINEERS. 

 March 9. — The President in the Chair. 



" Deicription of the Arched Timier Viaducts on the Newcastle and North 

 Shields Railway, erected from the designs of Messrs, John and Benjamin 

 Green ; and on the aj/plication of the same system of construction to obliqve 

 and other JSridges, to the Roofs of Railway Stations, and to otiier large Build- 

 ingt." 15y Benjamin Green. 



The coustruction of viaducts and bridges forms so important an item in the 

 cost of a railway, tbat the engineer is induced to device new methods of com- 

 pleting his works with due regard to stability and durability, and at the same 

 time with the least possible expense. Stone and brick have been the mate- 

 rials most generally used for bridges ; cast iron has been introduced where 

 the heights were too low for the spans, in large arches, or in trussed beams 

 where a certain clear space beneath was required, with only a limited height 

 to the level of the rail. Timber, from its lightness, strength, and cheapness, 

 has been extensively used, but only in spans of limited extent, owing to the 

 »ole mode of its application being by framed trusses, upon the same principles 

 SB those usually employed for roofing. 



These considerations induced Mr. John Green, as far hack as the year 1S27, 

 to make a design and model for a bridge, with timber arches resting upon 

 stone piers. In 1833 the plan was adopted, and in 1837 it was put into exe- 

 cution at the Ouse Burn Viaduct, where the construction was of great extent, 

 and the cost was an important consideration. 



The Viaduct is 018 feet in length, and 108 feet in height from the bed of 

 the river. There are five arches, the versed sine 33 feet, and the radius 68 

 feet; three of them are 116 feet span each, and two are lit feet each : two 

 •tone arches of 40 feet span each have been introduced at each end to give 

 length to the abutments, and to prevent the embankments from being brought 

 too near to the steep sides of the ravine. The piers are of stone : the spring- 

 ing stones for the three ribs, of which each arch is composed, are on offsets, 

 within -10 feet of the top of the piers ; cast-iron sockets are there bedded in 

 the masonry, and secured so as to receive the feet of the ribs. Two of the 

 piers are placed upon ))iles ; the others are founded upon the rock ; immedi- 

 ately beneath the centre of one of them an ohi coal-pit shaft was discovered, 

 and close adjoining to it the remains of the working of a coal scam : both were 

 rendered secure by being filled up with grouted rubble masonry. 



The ribs for the arches are composed of planks of Dantzic deal (Kyanized) : 

 the lengths vary from 46 feet to 20 feet, liy II inches wide and' 3 inches 

 thick: they are so disposed, as that the first course of the rib is two whole 

 deals in width, the next is one whole and two half deals, crossuig the joints 

 longitudinally as well as in the depth. Each rib consists of fourteen deals in 

 thickness, bent over a centre to the required form, and secured together liy 

 oak treenails I J inch diameter at intervals of 4 feet apart, each treenail tra- 



versing three of the deals. A layer of strong brown paper dipped in boiling 

 tar is placed between the joints, to bed them and exclude the wet. Trussed 

 framings and beams are secured upon the arched ribs; the platform composed 

 of planks, each 1 1 inches wide by 3 inches thick, is spiked down and covered 

 with a composition of boiling tar and Urae mixed with gravel in laying on, 

 forming a coating impervious to the wet ; upon this platform the two lines of 

 radway are laid, leaving a foot-path between them. 



The centreing for turning the ribs was very light and simple, and as every 

 convenience was afforded by having a railway with travelling cranes along 

 the sides of the piers, a whole centre could be moved by twenty men from 

 one arch, and fixed in another in one day. 



The author then describes the construction of the Welhngton Viaduct, and 

 that which has been erected by him at Dalkeith for the Duke of Buccleuch; 

 giving the relative costs of the three structures which have been mentioned, 

 and stone biuldings of the same dimensions : whence it appears that in the 

 Oiise Bum Viaduct there was an economy of £9000, resulting from the 

 adoption of this system. 



lie then shows the application of this system to the stnicture of oblique 

 bridges, particularly where a certain clear space is required beneath, and the 

 total height is limited : this is illustrated by a description of a bridge of 71 

 feet span, on the Newcastle and North Shields Railway, which crosses the 

 turnpike road at Walker, and by one erected over the lUver Wear on the 

 West Durham Railway. 



He describes also the application of the same system to the extensive 

 buildings and sheds of the Shields Railway Station ; to churches and to pri- 

 vate houses ; in the latter the arched form is very advantageous in gaining 

 space for the upper rooms, showing at the same time the economy resulting 

 from the adoption. 



The paper is illustrated by a series of nine elaborate detailed drawings, 

 showing the application to every kind of construction. 



Mr. Rendel remarked, that on those radways where first cost was a matter 

 of importance, the introduction of a superior kind of Timber Bridge was a 

 great desideratum. The communication proposed the application of tarred 

 paper between the joints , from experience be could not recommend either 

 paper or felt in such situations. He found that both substances prevented 

 the intimate contact of the surfaces of the timber ; in all framings exposed to 

 the action of the weather the tar was absorbed by the wood ; the paper and 

 felt then became saturated with and retained the moisture, so that decay very 

 speedily ensued. The mode he at present adopted was to have all the joints 

 and mortices of the framings very closely fitted, leaving only sufficient space 

 at the edges to be caulked with oakum, and the joint run with pitch, like the 

 seams of the deck of a vessel. M'herevcr it was practicable, great advantage 

 would result from covering the joints with sheet lead, to exclude the mois- 

 ture and prevent the decay, which was the great bar to the more general use 

 of timber in many engineering works. 



Mr. Vignoles was inclined to think the curve of the arch was too steep ; he 

 should prefer its being flatter. He would not then enter into the subject, but 

 he would present to the Institution a large model of a Timber Bridge, and 

 with it a communication, explaining his views on this subject, which was one 

 to which he had ])aid much attention. 



Mr. Macneil had found constant tronhle to result from the decay of wooden 

 bridges. The Dalmarnoch Bridge, which had been erected about thirty years, 

 now demanded continual repairs; the struts were nearly all decayed at the 

 points of insertion into the cast-iron sockets. The original floor had been 

 replaced by one of teak wood. 



In answer to a question from the President as to the process of " Kyaniz- 

 ing" timber for the Hull and Selby Radway, Mr. Timperley described the 

 method pursued there. In a close cyhndrieal wrought-iron vessel, 70 feet 

 long and 6 feet diameter, filled with a solution of corrosive sublimate, the 

 timber was piled, leaving a space along each piece ; the air was then exhausted 

 by air-pumps to a vacuum of about 25 inches by the mercury gauge, and by 

 the apphcation of a force-pump, under a pressure of 100 tb. per square inch, 

 the solution w.as driven into the pires of the timber. From experiments he 

 had made he believed that the timber was thus thoroughly saturated, and 

 although sufficient time had not elapsed to give any correct result as to the 

 comparative diu-ation of the sleepers, he thought very favourably of the pro- 

 cess. 



The original cost of the timber, which was the best Riga Balk, squared, 

 was 5/. 10s. per load (50 cubic feet). The expense of "Kyanizing" about 

 400,000 culdc feet, including the interest of the first cost of the apparatus, 

 was between fourpence and fivepence per cubic foot. The process was carried 

 on with greater r.ipidity, and much more effectually, than it could have been 

 done in open tanks. 



Mr. Lowe was of opinion, that although the mechanical part of this process 

 appeared %-ery effective, it was not really so. There were chemical difficul- 

 ties : a certain length of time was required to dilute and extract the sap and 

 aqueous matter from the pores. The greater or less duration of the process 

 might in some measure account for the difference of the residts practically 

 obtained. Dry planks succeeded better than wet ones ; with sound dry tim- 

 ber any solution of the metallic salts, such as the sulphates of iron or copper, 

 was efficacious, but with wet timber he doubted whether any preparation 

 would he effectual. 



Mr. Cooper believed that in the process of " Kyanizing" the chlorine united 

 with the albumen, and formed chloride of albumen ; it was possible that in 

 the exhausting process the air contained in the timber would expand and 



