Such is the method of manufacturing caustic soda and chlorine by this process, which will doubtless have a most important bearing upon many trades and manufactures, more particularly upon the paper, soap, and bleaching industries. But the invention does not stop where we have left it, for it is stated that the process can be applied to the production of sodium amalgam and chlorine for extracting gold and other metals from their ores. It can also be utilized in the production of caustic and chlorate of potash and other chemicals, which can be manufactured in a state of the greatest purity. A very important consideration is that of cost, for upon this depends commercial success. It is therefore satisfactory to learn that the cost of production has been determined by the most careful electrical and analytical tests, which demonstrate an economy of over 50 per cent. as compared with present methods. Highly favorable reports on the process have been made by Dr. G. Gore, F.R.S., the eminent authority on electro-chemical processes, by Mr. W.H. Preece, F.R.S., and by Messrs. Cross & Bevan, consulting chemists. Dr. Gore states that the chemical and electrical principles upon which this process is based are thoroughly sound, and that the process is of a scientifically practical character. Should, however, the economy of production even fall somewhat below the anticipations of those who have examined into the process very carefully, it can hardly fail to prove as successful commercially as it has scientifically.
COMPLETION OF THE MERSEY TUNNEL RAILWAY.
On the 11th of January (says the Liverpool Daily Post) will be opened for traffic the new station of the Mersey Tunnel Railway at the bottom of Bold Street. With the completion of the station at Bold Street the scheme may be said to have been brought successfully to a conclusion. It was not until 1879, after the expenditure of 125,000l. upon trial borings, that the promoters ventured to appeal to the public for support, and that a company, of which the Right Hon. H. Cecil Raikes, M.P., was chairman, was formed for carrying the project of the Mersey Railway into effect. The experience of the engineers in the construction of the tunnel is not a little curious. It was proved by the borings that the position in which the tunnel was proposed to be bored was not only the most important from the point of view of public convenience, and therefore of commercial advantage, but was from the point of view of engineering difficulty decidedly the most preferable. In this position the cuttings passed through the sandstone rock, although on the Liverpool side the shafts were sunk through a considerable depth through "made" ground, the whole of Mann Island and the Goree being composed of earth and gravel tipped on the old bank of the river. Indeed the miners passed through the cellars of old houses and unearthed old water pipes; excavated through a depth of tipped rubbish on which these houses had evidently been built; and then came upon the former strand of the river, beneath which was the blue silt usually found; then a stratum of bowlder clay; and finally the red sandstone rock. Once begun, the works were pushed forward night and day, Sundays excepted, until January, 1884, when the last few feet of rock were cleared away by the boring machine, and the mayors of Liverpool and Birkenhead met in fraternal greeting beneath the river. The operations gave employment to 3,000 men working three shifts of eight hours each, but were greatly accelerated by the use of Colonel Beaumont's boring machine, on which disks of chilled iron are set in a strong iron bar made to revolve by means of compressed air. This machine scooped out a tunnel 7 feet in diameter; and by successive improvements Colonel Beaumont attained a speed of 150 feet per week, leaving the old method of blasting far behind. As the machine moved forward the rock behind was broken out to the size of the main tunnel and bricked in in short lengths. One remarkable circumstance in connection with the work is that the boring from the Birkenhead side and the boring from Liverpool were found, when they were completed and joined, to be out of line by only 1 inch.
This excellent result was attained by careful calculations and experiments with perpendicular wires kept in position by weights, which, to avoid oscillation, were suspended in buckets of water. From shaft to shaft the tunnel is 1,770 yards in length and 26 feet in diameter; but for a length of 400 feet at the James Street and Hamilton Square stations the arch is enlarged to 50½ feet. The tunnel is lined with from six to eight rings of solid brickwork embedded in cement, the two inner rings being blue Staffordshire or Burnley bricks. For the purpose of ventilation a smaller tunnel, 7 feet in diameter, was bored parallel with the main tunnel, with which it is connected in eight places by cross cuts, provided with suitable doors. Both at Liverpool and at Birkenhead there are two guibal fans, one 40 feet and the other 30 feet in diameter. The smaller, which throw each 180,000 cubic feet of air per minute, ventilate the continuations of the tunnel under Liverpool and Birkenhead respectively, and the larger tunnel under the river. The fans remove together 600,000 cubic feet of air per minute, and by this combined operation the entire air in the tunnel is changed once in every seven minutes. By the use of regulating shutters the air passes in a continuous current and the fans are noiseless. The telegraph and telephone wires pass through the tunnel, thus avoiding the long detour by Runcorn. Probably, as a feat of engineering, the construction of the new station at Bold Street is not inferior to any part of the scheme advanced. Under very singular and perplexing difficulties it could only be proceeded with in its first stages from midnight until six o'clock the following morning, it being of course essential that the traffic at the Central Station should not be interfered with. During these hours, night after night, trenches were cut at intervals of 10 feet across the roadway connecting the arrival platforms at the station, and into these were placed strong balks of timber, across which planks were laid as a temporary roadway. Beneath these planks, which were taken up and put down as required, the rock was excavated to a depth of 9 feet, and the balks supported upon stout props. Then from the driftway or rough boring beneath well holes were bored to the upper excavation, and through them the strong upright iron pillars designed to support the roof of the new tunnel station were passed, bedded and securely fixed in position. No sooner were they in situ than the most troublesome part of the task was entered upon, for the balks had then to be removed in order to allow to be placed in position the girders running the length of the new station, and resting on the tops of the upright pillars. From these longitudinal girders cross girders of great strength were placed, and between these were built brick arches, packed above with concrete. This formed the roof of the new station. One portion of it passed under the rails in the station above, and had to be constructed without stoppage of the traffic. The rails had consequently to be supported on a temporary steel bridge of ingenious design, constructed by Mr. C.A. Rowlendson, the resident engineer and manager of the company, under whose personal supervision, as representing Sir Douglas Fox, the work has been carried out. With this device the men were enabled to go on in safety although locomotives were passing immediately above their heads. After the completion of the roof the station below was excavated by what is technically called "plug and feather" work—that is to say, by drilling holes into which powerful wedges are driven to split the rock.
A STEAM STREET RAILWAY MOTOR.
While in Paris, President Yerkes, of the North Chicago Street Railway Company, purchased a noiseless steam motor, the results in experimenting with which will be watched with great interest. The accompanying engraving, for which we are indebted to the Street Railway Review, gives a very accurate idea of the general external appearance. The car is all steel throughout, except windows, doors and ceiling. It is 12 ft. long, 8 ft. wide, and 9 ft. high, and weighs about seven tons. The engines, which have 25 horse power and are of the double cylinder pattern, are below the floor and connected directly to the wheels. The wheels are four in number and 31 in. in diameter. The internal appearance and general arrangement of machinery, etc., is about that of the ordinary steam dummy. It will run in either direction, and the exhaust steam is run through a series of mufflers which suppress the sound, condense the steam and return the water to the boiler, which occupies the center of the car. The motor was built in Ghent, Belgium, and cost about $5,000, custom house duties amounting to about $2,000 more.—The Railway Review.