1849.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



191 



If these plans are carried out, it will be necessary to abolish all cess- 

 pools, so that all the valuable mailer that now flows into them may be 

 conieyed away to the collecting tanks, where it will subside and undergo 

 the process of deodorization and distribution. 



Courts.— Our courts are what are usually denominated Cul de Sacs, and 

 but few, if any of ihem, are of an area suflicient for the number of the in- 

 habitants, if we allow the usual average of 25 square yards for each in- 

 dividual, the minimum area that health demands. Being very narrow, and 

 generally closed at one or both ends, they are very imperfectly ventilated, 

 anil therefore a larger area per inhabitant should be afforded them, if the 

 health of the city is to be maintained; or the number of the inhabitants 

 should be reduced to the minimum the space will allow, according to the 

 preceding scale. 



NOTSS OF "ZnS r<£CNTK. 



The Floating Railway Bridge for the Frilh of Tag. — This novel and fx- 

 traordinary piece of naval architecture has had her engines fitted at Mr. 

 Napier's dock, at Lancefield. She lately made an experimental trip down 

 the river to Greenock and hack. The vcsssel is of iron, 175 ft. long, 34 feet 

 broad, and 10 feet deep, the bottom being a very flat curve ; both ends are 

 alike, and quite square, so as to abut against the quay, and receive the 

 trains on deck from either end. The deck is flush, and clear fore and aft, 

 and on it are three lines of rails, so as to enable it to take the longest train 

 likely to require it. The steering wheel is amidship, elevated between the 

 paddle-boxes, and connected with the rudders at each end by long chains ; as 

 the vessel will not he turned, these rudders will, of course, be used alter- 

 nately, as either end becomes the stern. There are two engines entirely in- 

 dependent of each other, and instead of a shaft connecting the pa.idles, 

 each is moved solely by one engine, by which means extraordinary com- 

 mand is obtained over the movements of the gigantic machine, independent 

 of the rudders. The diameter of the cylinders is 56 inches, with a 3 ft. 6 in. 

 stroke; the valves work with great ease, and each engine is 100-horse 

 power. The valve gear is on deck ; there are two eccentrics which are 

 tlirown alternately in and ont of gear, as either end of the vessel becomes 

 in turn the head. The boilers are amidships, with a clear space all round 

 for facility of cleansing and repairs. Slie draws but little water, made eight 

 knots per hour, and is expected to be in operation in two months. There 

 are two small extra pumps for supplying the boilers, in case of the water 

 running low, and every precaution appears to have been taken to prevent 

 accident. 



Marine Engines. — Mr. Napier, of Glasgow, is now constructing a pair of 

 engines for the American mail steamers, with cylinders 9G inches diameter. 

 When completed they will be nearly 900-horse power. 



Exhibition of Machinery at Ghent. — A special exhibition of machinery, 

 frames, looms, and implements of trade (of Belgian or foreign make) em- 

 ployed in the manufacture of yarns and tissues of all sorts, is to be opened 

 at Ghent (on the occasion of the exhibition of the produce of the indu try 

 of Flanders) in the month of July. Special rewards, consisting of com- 

 memorative medals, of gold, silver, and bronze, will be awarded to such ex- 

 hibitors as shall appear to merit such a distinction. 



Mode of Silvering Glass hy the Employment of Gun-cotton. — M. Vohl 

 has recently discovered that a solution of gun-cotton, in a caustic ley, pos- 

 sesses, in a high degree, the property of precipitating silver from its solutions 

 in the metallic form. In fact, on bringing gun-cotton into contact with a 

 caustic ley, of sufficient strength, the cotton will become dissolved in the 

 ley, giving out ammonia with a considerable degree of heat, and producing 

 a deep brown liquor, somewhat thick ; on pouring an acid into this, a brisk 

 effervescence is produced, carbonic acid and nitrous acid being disengaged. 

 The action of the gun-cotton, in this instance, shows that it is not simply 

 dissolved, but undergoes decomposition, by which the atoms of oxygen, in 

 the nitric acid, enter into combination with the atoms of carbon in the gun- 

 cotton, thus producing carbonic acid, which, as well as the nitrous acid pro- 

 duced by the nitric acid, combines with one part of potash. A fresh decom- 

 position of nitrous salt by the potash, in presence of hydrogenated sub- 

 stances, furnishes ammonia. The most remarkable property of this alkaline 

 solution is the following: — On pouring into it a few drops of a solution of 

 nitrate of silver, and adding ammonia until the oxide of silver formed is re- 

 dissolved (the mixture being slowly heated in a water bath), the liquor will, 

 at a certain period, assume a dark brown colour, and eflfervescc, the whole of 

 the silver being precipitated on the sides of the vessel. The mirror thus 

 produced is much superior in brilliancy to those produced by means of etherial 

 oils or ammoniacal aldehyde; and the facility with which it is produced 

 will doubtless render it of practical importance. This property is not exclu- 

 sively possessed by gun-cotton ; it is found also in cane sugar, sugar of 

 milk, manna, gums, and other substances which may be rendered explosive 

 liy treating them with nitric acid. Picro-aznic acid produces, under the 

 same circumstances, a reflective metallic surface; and it appears that this 

 reaction takes place with all bodies which, when treated with nitric acid, do 

 not furnish products of oxidation, but another series of bodies which admit 

 of carbonic acid for forming one of their constituent parts, since they at 

 the same time give up an equivalent of water. — Tecknologiste. 



Method of Cleaning Vessels and other Articles of Silver. — Boil thirty 

 grammes of finely pulverised and calcined hartshorn in a quart of water, 

 and while on the fire put as many silver articles in the vessel used for boiling 

 as it will hold, and leave them there for a short time ; then withdraw them, 

 and dry them over the fire. Continue this until all the articles have been 

 treated in the same manner. Then introduce into the hartshorn-water clean 

 woollen rags, and allow them to remain until saturated; after which, dry 

 them and use them for polishing the silver. This is also the best substance 

 which can be employed for cleaning locks and brass bandies of room doors. 

 When the silver articles are perfectly dry, they must be carefully rubbed 

 with a soft leather. This mode of cleaning is excellent, and much prefer- 

 able to the employmeut of any powder containing mercury, as mercury has 

 the effect of rendering the silver so brittle as to break on falling. — Ibid. 



Method of Soldering Cast-iron with Wrought-iron. — The following pro- 

 cess has been recommended for this purpose : — First melt filings of soft cast- 

 iron with calcined borax in a crucible; then pulverise the black vitreous sub- 

 stance which is thereby produced, and sprinkle it over the parts which are 

 intended to be united; after which, heat the pieces of cast and wrought iron 

 and weld them together on an anvil, using only gentle blows. This method 

 is peculiarly applicable for the manufacture of iron articles which are in- 

 tended to be made red hot, and are required to be impervious to fluids or 

 liquids ; as such a result cannot he obtained by simple fastening. — Ibid, 



Self-Lighting Gas Burner. — A self-igniting gas-burner, invented by Mr. 

 Strode, of St. Manin's-le-Grand, is an adaptation of the zinc hydrogen, or 

 Duhriener's light, to the purpose of lighting a jet, or other burner, of coal- 

 gas. In this case, however, the hydrogen gas is generated in an impi-oved 

 manner by the galvanic action of a small battery of amalgamated zinc and 

 platinised silver plates, immersed in sulphuric acid, diluted largely with 

 water. The hydrogen gas so generated, is directed through a fine jet on a 

 hall of spongy platinum, and, when ignited, moved across the coal-gas 

 burner. The two cocks are ingeniously connected by means of a brequet 

 movement ; and an instantaneous light is thus produced by one movement 

 of the hand. The eff^'ct is magical, and pretty in the extreme ; and the ap- 

 paratus, which is small and portable, is a very becoming burner for the office 

 desk or library table, where we have no doubt it will be extensively used and 

 appreciated, as soon as Mr. Strode shall have announced it as ready for 

 general sale. So far it has only been used privately in the way of experi- 

 ment ; but several months' constant use have served to prove its perfect uni- 

 formity of action. The safety it affords, by the avoidance of the use of 

 lucifer matches, is a consideration which will weigh with the prudent; and 

 the ease with which it is lighted and extinguished, will be very valuable, if 

 only in the avoidance of unnecessary heat. For chambers, bed-rooms, offices, 

 and libraries, in private houses, and for the ball table at night, it is perfect, 

 and, above all, safe. It is also easily connected to the ordinary gas branches 

 by a union connection fitting the common burner screw, and a flexible or 

 other tube. 



Machine for Manufacturing Envelopes. — M. RiSraond, of Birmingham, has 

 just constructed a very ingeidous and complete machine for the manufacture 

 of envelopes. The machine, we are informed does its work in a very elB- 

 cient and admirable manner, the envelopes which it turns out being more 

 perfect and uniform in their construction than those produced by hand in 

 the ordinary manner ; but tlie quantity of work which the machine accom- 

 plishes is the most astonishing. Supposing it to be turned by manual labour, 

 one man, with the aid of three or four young girls or boys to gather the 

 envelopes, would, it is calculated, by its lueaus, be able to manufacture from 

 30,000 to 3.5,000 in an ordinary working day, the paper being cut before- 

 hand ; while an expert baud, in the ordinary way, exclusive of the cutting, 

 cannot, upon the average, make more than 2,000 in the same manner as 

 those in question, which have a device stamped upon them at the point 

 where the seal is usually placed. 



Stvivel Bridges. — Mr. Dodd, of St. Vincent-street, Glasgow, has designed 

 a swivel bridge, for the Midland Junction liaihvay, to cross the Clyde canal 

 at Falkirk. The two main beams of the bridge are constructed of hollow 

 rectangular panelled tubes of wrought-iron, stretching across the water-way ; 

 they are stayed transversely by wrought-iron tension-rods and diagonal 

 timber-frames, and are further supported from the centre cast-iron pivot by 

 four cast-iron box-beams, which act as struts, and convey the strain from the 

 roadway to the top of the pivot. Two open ornamental cast-iron frames rest 

 one on each side of the upper circular plate of the pivots, and ate attached 

 together at top by a capital, and carry the saddle for two dia.;onal tension- 

 rods, bolted to the girders, which they stifi'en to a great extent. The pivot 

 is in form of an inverted truncated cone, c\lindrical at its U|)per end, where 

 it is guided hy a set of stationary anti-friction pulleys. The bottom enters a 

 small chamber through a water-tight stuffing-box, in connection with a 

 hydrostatic ram, by which water can be pumped in beneath the cone, whiL-h 

 will elevate the whole structure, sufficient to clear the bearings, when it can 

 be swivelled round. This is eft'ected by two hydraulic rams, placed horizon- 

 tally at right angles with each other, working a shaft, around which and 

 the cylindrical top of the pivot, is an endless chain, the communication of 

 the movement of the rams to which may be effected by the adoption of 

 various mechanical arrangements, according to circumstances. 



Guildford Drainage. — The various plans for the drainage of Guildford, 

 sent in competition, were submitted by the committee to Mr. Ilosking for 

 examination, to assist them in making the award. Three plans have been 

 selected for final consideration — " Pioneer," " Specula," and " C. Engineer." 



