1847.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



203 



The advantages expected from this mode of ventilation, are, 1. The pre- 

 vention of local draughts. 2. The prevention of the stains and disfigure- 

 ments resulting from such draughts. 3 The avoidance of all movement 

 and dispersion of dirt and dust of the house by currents occasioned in it, 

 which currents, if existing, would tend to render the air impure. 4. The 

 avoidance of all sudden change of temperature. Finally, it was noticed 

 that all parts of the house were fire-proof. Mr. Faraday then took occa- 

 sion to remark that this scheme of ventilation was under a disadvantage in 

 the present case, as it had to be adapted to buildings which were not plan- 

 ned with reference to it. 



DREDGE'S SUSPENSION BRIDGES IN INDIA. 



Major Goodwyn has addressed the following letter to the Editor of the 

 Englishman (Published in India in reply to Mr. Dredge's remarks): — 

 " Sir, Adverting to a statement which lately appeared in your paper, and 

 ■which, with certain commenls, has found its way into the Star and 

 ]ila(lras Spectator, relative to the failure of an iron bridge on the taper 

 chain principle, manufactured by the patentee, Mr. Dredge, sent out by 

 him, and put up at Jessore, I feel myself bound to offer a few words, as 

 the measures of the Government have been misrepresented, and the facts 

 of the case considerably distorted. The span, width of roadway, height of 

 point of suspension, being necessary data to furnish Mr. Dredge witli, 

 these dimensions, and these alone, as connected with the required strength 

 of the iron- work, were sent to him, and he was further particularly instructed 

 to form the eyes of his links in a peculiar way (which, however, he did 

 not observe). Mr. Dredge, as I before said, required the above data on 

 which to calculate the strength of his ironwork, and the angles at which 

 his rods were to be placed. Not one of these details was sent from here, 

 nor was it likely he would have adhered to them if they had been, for it 

 ■was naturally his interest to protect his patent by every care he could be- 

 stow, and it is sufficiently evident he did attempt it when he made the longi- 

 tudinal beams 2.5 per cent, above what he was in the haljit of doing, not ' as 

 the drawings warranted,' for no drawing went from this country, saving 

 a tracing of the masonry design, and section of the river, with sundry 

 queries relative to the retention of the chains in the ground. To prove 

 that the drawings of the iron-vTork came out from, instead of going to Mr. 

 Dredge, I send you his sheet of plans, which were accompanied by most 

 elaborate injunctions, all of which were fulfilled, and the bridge was most 

 correctly put up. Yet the bridge fell, though it might have been standing 

 now if it had only been subjected to the ordinary traffic of the country, 

 and guarded from the unusual crowd to which it was exposed. 



"1 have said already more than I intended; suffice it to add, that once 

 a sincere admirer of the system, I have had experience enough to discover 

 its defects ; full explanations and refutations of Mr. Dredge's statement 

 have been sent to the scientific journals in England, and will appear in 

 due course, as will also an elaborate treatise on the system in all its bear- 

 ings : let the discriminating public wait a little, and hear both sides of the 

 question." 



NOTES OF THE MONTH. 



Centre Punch. — It is customary, in moving the " centres" of a piece of 

 iron intended to be turned, to drive a centre punch into the holes previously 

 made ; first, at an angle, in order to force tiie metal over to the side re- 

 quired, and then, to drive it in, perpendicularly, in order to give the hole the 

 proper shape for the lathe centres. This is frequently repeated, until the 

 hole is mutilated, or driven so deep as to be objectionable, and is absolutely 

 barbarous on a nice piece of work. There are other modes of moving the 

 centres of accurate work, such as the scraper and centreing drill, but this is 

 the mode generally adopted on account of convenience, and has done injury 

 to much fine machinery. The new plan adopted for this 

 purpose, which I saw in a small shop at Massuchusetts, appears 

 to me to be equally convenient with the ordinary centre-punub, 

 while it is quite as perfect and unobjectionable as any of the 

 more tedious modes. This tool is formed by making the conical 

 point of a centre-punch on an angle with its shaft. It will be 

 readily seen that by using this punch, the hole will be more 

 easily moved laterally, that its uniform conical shape will be 

 preserved perpendicular, and that the distance of moving it may 

 be accurately managed by the blow of the hammer upon the 

 punch. — P. B. TrLER, New Orleans. 

 Skimming Ladles for Pouring Cast Iron. — In a foundry at Connecticut, 

 there is a mode of skimming small ladles for pouring cast iron, which is 

 found to be very useful. It consists in riveting a small bar of iron across 

 the top of the ladle, just at the back of the mouth, and covering it with 

 clay, the same as at the bottom of the ladle, to prevent its cooling the 

 melted iron. The bar should extend far enough below the top of the ladle 

 to commence skimming from the first, and near enough to the mouth to 



continue until all is poured. I saw some ten or fifteen persons pouring with 

 these ladles, while not one was required to skim, and I was told that no 

 objection was found to it in any respect. — Ibid. 



The most ExtcHsire Manual Structure is, undoubtedly, the great Chi- 

 nese wall. It is 24 feet high and 10 feet wide, and reaches to the extent 

 of from 2,000 to 2,400 miles, over mountains, precipices, and rivers, up to 

 the sea on one side, and the inaccessible mountains of Thibet on the other. 

 The (Chinese truly call it one of their wonders of the world — as the slone 

 used for its construction, if placed one beside the other, would suffice to 

 encompass the whole circumference of the globe. The entire history of 

 this construction is wrapt in similar obscurity with that of the Pyramids 

 of Egypt. Chinese documents ascribe to the founders of the empire the 

 benefit of a vast system of drainage and exsication of the land, after which 

 came the great world-dearth of seven years, &c. 



Malleable Glass. — Prof. Schonbein has discovered a substitute for glass. 

 It consists of pulp of common paper, made transparent, by causing it to 

 undergo a certain transformation, which the Professor calls catalytic. With 

 this paper, made waterproof, is manufactured perfectly transparent window- 

 panes, vases, and bottles, which will not easily break. 



Dover Landing Pier. — The lords of the Admiralty have at length been 

 pleased to give their sanction to the erection of a landing pier in Dover 

 Bay, according to the plans prepared by Messrs. Birch, and submitted to 

 them by the Town of Dover. The commissioners of the harbour also have 

 given their assurance that the measure shall meet with every assistance from 

 them. A company is, therefore, now forming for the purpose of carrying 

 out this desirable work, and it is determined to use every endeavour to get 

 the erection completed during the present season. The pier will extend 800 

 feet into the sea, and at its extremity will be a lozenge construction of four 

 sides, afl"ording to steamers not only unusual accommodation iu coming 

 alongside, but the certainty of a good lee in stormy weather. The advaa 

 tages of the pier will be greatly felt by the mail establishments of the Bri- 

 tish and foreign governments, who have expressed their willingness to enter- 

 tain the question of an annual grant for its use, — as well as by the conti- 

 nental steamers, who will thus be enabled to effect a landing of passengers 

 at low tide, which is a question of great importance to Dover, and enables 

 it to maintain its high position as a point of embarkation to the continent. 



" The Express" steam vessel, built for the South M'estern Steam Naviga- 

 tion Company for the Southampton and Havre station, by Messrs. Ditchburn 

 and Mare, and fitted with engines by Messrs. Maudslays and Field, made an 

 experimental trip on the Thames on the 4th ult. It is stated she performed 

 the distance from the Nore lights to Blackwall, a distance of 47 miles, in 

 2 hours and 8 minutes. {Qy. with tide.) 



Brighton and Continental Steam Packet Company — The two boats built 

 for this company have been running from Shoreham to Havre since the 1st 

 ult., and have answered the directors' expectations in every respect. One of 

 the boats ran the distance (84 nautical miles) in G| hours. When the 

 Dieppe railway is open, Dieppe will be the port instead of Havre. When 

 the works at Newhaven are completed, that port will be the place of depar- 

 ture instead of Shoreham, by which a saving of J or J- of an hour will be 

 effected, and in fine weather the boats will frequently go over in about four 

 hours. 



Railway Opened. — On the 20th ult., a further extension of the South 

 Devon railway, from Newton to Totness, a distance of 8| miles, was opened. 



Short Time for Building Operatives. — We are happy to state that a system 

 of leaving off work on Saturdays at 4 o'clock is about to be carried out : it 

 has, we understand, been already adopted among the carpenters and joiners 

 of London, in the shops of Mr. Thomas Cubitt, Mr. William Cubitt, Mr. 

 Baker, Mr. Piper, Mr. Jackson, Mr. Lee, Mr. Seth Smith, &c. 



Prevention of Iron from Rusting. — The Royal College of Chemistry ofi'ers 

 a premium of f 1,000 for the discovery of a method of rendering iron, when 

 used for ordinary purposes, as little liable to rust as copper. 



Printing Types. — M. Coblentz, a topographic printer in France, states that 

 type may be hardened by galvanism. 



Grindstones. — M. Jules Pugeot, of Herimoncourt, has adopted a plan to 

 preserve bis workmen from the ill effects presented by the use of grindstones 

 in his factory, by applying a ventilator to carry off the siliceous dust before 

 it can reach the mouth or nostrils. 



Conversion of Diamonds into Coke. — At the meeting of the British Asso- 

 ciation, Dr. Faraday exhitiited some diamonds, which he had received from 

 M. Dumas, which had, by the action of intense heat, been converted into 

 coke. In one case, the heat of the flame of oxide of carbon and oxygen 

 had been used— in another the oxy-hydrogen flame — and in the third the 

 galvanic arc of flame from a Bunsen battery of 100 pairs. In the last case, 

 the diamond was perfectly converted into a piece of coke — and in the others 

 the fusion and carbonaceous formation were evident. Specimens iu which 

 the character of graphite was taken by the diamond, were also shown. The 

 electrical character of these diamonds were stated also to have been 

 changed — the diamond being an insulator, while coke is a conductor. 



Iron for Girder Bridges. — Mr. Murray, a valuable contributor to the 

 Mining Journal, suggests that iron girders and similar supports ought never 

 to be made of cast iron, but of wrought iron, and composed of plate ; 

 twisted previously into a rope, and finally moulded into the required forms 



