to establish telegraph stations at distances not greater than five miles apart, the connexion between them being made by separate wires, and exclusively appropriated to railway signals, and not extending continuously further than from one station to another. Whenever an obstruction occurred on the line, it should be signalled in both directions, and no train should be allowed to leave any railway station until a signal had been received from the telegraph station in advance that the line was so far clear. By the adoption of a short code of signals, these communications could be transmitted with great facility, and should any inconvenience be in the first instance experienced at junctions and cross-lines, he had no doubt that a little experience, and adaptation of the arrangements to the special circumstances, would soon remove it. The expense of such a complete system of telegraph signalling would be more than compensated to the railway companies by the avoidance of collisions, and, viewing it only in an economical point of view, the Directors would find it to their advantage to adopt such a plan. As an illustration of the pecuniary losses which railway companies sustain in consequence of accidents by collisions, Dr. Scoresby mentioned the case of a friend of his, a clergyman, who received such severe injury by a collision, that he would be for the rest of his life laid upon his back, unable to perform his clerical duties, and he and his family had to be supported at the cost of the railway company.

On Railway Collisions, with Suggestions for their Prevention. By the Rev. F. F. STATHAM.-The plan proposed by Mr. Statham, is to prevent collisions by adopting a more effectual means of retarding trains in motion, so that they may be brought to rest within a distance of fifty yards. He made three suggestions, the first of which was, to retard a train in motion by the expansion of wings, or of fans, to increase the resistance of the air; the second was, to employ an electro-magnetic brake, acting directly on the rails by the attraction of electro-maguets fixed to the carriages; and the third was, to cause jets of steam to issue from the front of the engine, and thus obtain a reacting resistance from the air.

In the discussion that ensued all the plans were considered. Mr. Statham's fan-retarder was shown to be altogether impracticable, since, to oppose any effectual resistance would require an expansion of acres of surface; nor were the electro-magnetic brake and the steam jets considered of much more practical utility. Dr. Scoresby's plan of telegraph signals was approved by several members, as being a more perfect carrying out of the plan which is now adopted; the chief novelty of the proposition consisting in the establishment of district wires and stations at short distances for railway purposes. Mr. Nelson, who has paid much attention to railway statistics, adduced the following curious computation in illustration of the comparatively few deaths caused by railway accidents: That if a person were born in a railway carriage, and were to be continually traveling on railways till he was killed by an accident, he would, according to the average number of passengers and deaths, live 960 years.

A Description of some of the large Valves and other Machinery which have been employed for the Discharge of Water at the Manchester Water Works. By J. F. BATEMAN.-Mr. Bateman described, at great length, the sources of supply and the means adopted for conveying the water

from the different collecting reservoirs to the service-reservoir in Manchester, and the peculiar valves required to cut off and regulate the water supply to the inhabitants. The magnitude of the Manchester Water Works was stated to be greater than that of the Croton Aqueduct at New York, which has been hitherto considered the largest of modern times. The three principal reservoirs will contain 500,000,000 of cubic feet of water, and there are two smaller reservoirs which hold 100,000,000; so that the total quantity stored up for the consumption of Manchester and the neighboring mills is 600,000,000 cubic feet. The furthest reservoir is 20 miles distant from Manchester, and is 420 feet above the level of the upper part of the city. The daily consumption of the inhabitants is 30,000,000 gallons, which are supplied immediately from a service reservoir 150 feet above the level of Piccadilly, at the highest part of Manchester. The valves of the main pipes which open and cut off the supply are 40 inches in diameter, and with a pressure of 150 feet on that area, it would have been impossible, without great labor of complicated machinery, to have opened and closed the valves had they been of the ordinary construction. Mr. Armstrong, of Newcastle, suggested, as a means of overcoming the difficulty, that the large valve should be divided into three, and this plan had been found to act remarkably well. A small compartment of the valve was first withdrawn, and the rush of water through it having filled the pipe, the pressure was counteracted, and the other and larger divisions of the valves could then be easily lifted. By this contrivance the mains could be opened and closed by one man. Another object to be accomplished was to arrest the flow of water in case the large pipes with such a pressure upon them should burst and flood the neighborhood. This was successfully effected by introducing into the main pipe a kind of flood gate, which was opened at a certain angle by the ordinary flow of the water, and at that inclination it held suspended, by means of a lever, a heavy weight connected with a throttle valve. When the rush of water greatly exceeds the ordinary flow, a catch that retains the lever is withdrawn, and the fall of the weight closes the throttle valve and stops the flow. This self-acting machinery has more than once prevented serious damage that would have arisen from the bursting of the pipes. Another contrivance invented by Mr. Moore, a gentleman in Mr. Bateman's office, deserves mention. The water in the reservoirs is generally beautifully clear, but during heavy rains it becomes turbid, and would be unfit for the consumption of the inhabitants without being filtered. To avoid the inconvenience and expense of filtration, Mr. Moore suggested a plan for separating the turbid water from the clear. A weir was constructed, over the edge of which, during dry weather, the water in the reservoir flows perpendicularly into a drain pipe immediately below, which conveys the clear water to the service reservoir; but in heavy rains, when the water is turbid, the extra flow shoots it over the first drain into a second, to convey it to the reservoirs that supply water power to the mills. By this simple arrangement the turbid and clear waters are separated, and it is calculated that a saving of 100,000l. has thus been effected. In supplying Manchester with water, a new kind of fire-plug has been adopted, consisting of a gutta percha spherical valve, which closes the apertures, and when the water is required to escape, an instrument is intro

duced which forces down the valve. The great water pressure in the pipes forces it so high that there is no necessity for fire engines; and the effectual manner in which fires are extinguished by the torrent of water that can be thus applied has greatly diminished the cost of insurance in that city. Mr. Bateman stated, that in large establishments the diminished premiums on fire insurances produced by the increased facility of extinguishing fires are sufficient to pay the water rate. Several other arrangements of minor importance which have been introduced in the Manchester Water Works were also described by Mr. Bateman.

Telegraphic Progress.*

The Magnetic Telegraph Company effected their communication between this country and Ireland on Monday week, when their new cable between Donaghadee and Portpatrick was successfully laid down.

The prospectus has been issued of an association, under the title of the Mediterranean Electric Telegraph Company, formed with the object of uniting Europe with Africa, the East Indies, and Australia, by way of France, Piedmont, Corsica, Sardinia, Algeria, and Egypt. The route is said to have been carefully surveyed. The company are making arrangements for the construction of a subterranean line along the coast of Africa, from Algeria to Alexandria; and with the aid of the British Government and the East India Company, the wires may be prolonged across the Desert, the Red Sea, Arabia, and Persia, to meet the great Indian line of 3000 miles, now in course of construction by the East India Company, and which may eventually be extended to the Australian colonies. The capital is 300,000l. in 30,000 shares, of 107. each, deposit 4l. per share. The Government of France is said to have guaranteed interest on 180,000l. and that of Sardinia on 120,000l. A contract has been entered into for the complete execution of the works from Spezzia to Tunis, including all preliminary expenses, and a transfer of the concessions, with exclusive privilege for fifty years, for the sum of 300,000l., the amount on which interest has been guaranteed. The works are said to be already in active progress in Sardinia.

In a lecture delivered at Belfast a few weeks ago, Mr. J. B. Lindsay said that he had recently instituted a series of experiments with the view of testing an idea that he had formed some fifteen years ago that no submarine wires are necessary for the transmission of electricity. In explanation of this principle, he said, "Suppose a wire connected with the copper end of the battery to be let down to the shore, and connected with a sheet of metal laid in the river. Suppose a wire from the zinc end taken to Broughty Ferry, and soldered to a metallic plate placed also in the river. Suppose similar plates laid in the river on the Fife side, at Newport and South Ferry, and these joined by a wire having in its course one or more telegraphs. Suppose now that a charge of electricity is sent through the wire on the Dundee side; this current may make its circuit from the copper to the zinc either by leaping four miles through the water from Broughty Ferry to Dundee, or by a leap of two miles across

* From the London Builder, No. 539.

the river to the other wire at South Ferry, and another leap of two miles from Newport to Dundee. In such a case, I have found that part of the electricity does not go across, and part of it does; but the part of it that does go across is sufficient to work one or ten thousand telegraphs." The possibility of this we long since noted.

Revolving Shutters.*

The shutter referred to by our correspondent, "J. F.," at Limerick, 45 feet long, is not so long by 6 feet as one erected by us at Water lane, Blackfriars, three years since,-passing round a corner, rolling in a space of 20 inches diameter, and opened and closed in 1 minute: we would have no hesitation in constructing a shutter 100 or even 200 feet long on this principle. The great difficulty is to make revolving shutters with horizontal laths of great width in one piece, as the shaft or roller can have no centre support. The shutter referred to in Fleet street is 24 feet wide and 18 feet high, in one piece, and is opened or closed with ease in 30 seconds. We have recently obtained a patent for some important improvements, first, the combining iron and wood in their construction, whereby great stiffness and lightness is obtained,-qualities, obviously of great importance; also for curving the laths of metal shutters in such a form that the joint, or hinge, is formed in the solid, greatly increasing the strength and appearance, and permitting them to be rolled in either direction, greatly facilitating their application.-Clark & Co.

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Experimental Researches to Determine the Strength of Locomotive Boilers, and the Causes which lead to their Explosion. By WILLIAM FAIRBAIRN, C. E.t

These experiments were undertaken in consequence of the explosion of a locomotive boiler in the engine house of the North-Western Railway Company, at Manchester. It may be remembered that the immediate cause of the explosion was owing to the engine driver having screwed down the safety valve while he was talking to a companion, and leaving it in that condition. In twenty-five minutes from the time the valve was screwed down, the boiler burst with tremendous force, blowing off part of the lofty roof, and killing several men who were within the building. The boiler was a complete wreck, scarcely any portion of it remaining entire. The government inspector, who examined the wreck of the boiler shortly after the explosion, reported that the stays of the fire box had been defective, and that the boiler had not been sufficiently strong for the ordinary work. Mr. Fairbairn entertained a contrary opinion, and contended that all the parts of the boiler had been strong enough to resist six times the usual working pressure, and that the accumulated generation of steam during the twenty-five minutes that the valve had been screwed down must have amounted to a pressure of 300 lbs. on the square inch. The government inspector, however, maintained that the time was not

* From the London Builder, No. 539.

From the London Civil Engineer and Architect's Journal, October, 1853. VOL. XXVI.-THIRD SERIES.-No. 5.-NOVEMBER, 1853.

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sufficient to have increased the pressure to nearly that amount. In consequence of this difference of opinion, a series of experiments were instituted to determine the real causes of the explosion, and to register those facts for future guidance in guarding against such catastrophes. In the first place, Mr. Ramsbottom, the locomotive superintendent, made some experiments with the stays of the burst boiler, from which it appeared that the force required to pull the old stays out of a copper plate (similar to that of the fire box), into which they had been screwed by the old threads only, and not riveted, was 340 lbs. on the square inch. Mr. Fairbairn said he had carefully repeated these experiments with nearly similar results; and assuming that the ends of the screws had been riveted, and sound in other respects, it might reasonably be concluded that a strain of not less than from 450 to 500 lbs. upon the square inch would have been required to strip the screws or to tear the stays themselves asunder. It should be borne in mind, that the exploded boiler, though recently repaired, had been made many years ago, and as the cylinders were only 13 inches in diameter, it had latterly been employed only as a pilot engine to pilot the trains through the Standedge Tunnel. The stays were 5 by 5 inches apart, whilst the stays of the boilers at present constructed are thicker and closer together, and form squares of 4 to 4 inches, by which increase of strength the resisting power would be raised to nearly 800 lbs. on the square inch.

With a view to determine by actual experiment the strength and power of resistance of the locomotive boiler, the Directors of the North-Western Railway Company placed at Mr. Fairbairn's disposal an engine, the exact counterpart of the one that exploded, both having been made at the same time by the same engineers, Messrs. Sharp and Roberts, of Manchester, and both having run the same number of miles. The engine experimented on was not, however, in the same state of repair as that of the exploded one, the fire box being considerably bulged, and the rivets as well as the stays much weakened. This boiler was subjected to hydraulic pressure, and when 207 lbs. on the square inch had been put upon it, one of the bolts of the cross bar over the fire box broke, which caused the experiment to be discontinued, as the leakage was greater than the force pump could supply. This experiment fully proved that the fire box stays on the comparative weakness of which so much stress has been laid-are not the weakest parts of a locomotive boiler; and that there is more to be feared from the top of the furnace, which, under severe pressure, is almost invariably the first part to give way. Great care, Mr. Fairbairn said, should therefore be taken in the construction of that portion of the boiler, and the cross beam should not only be strong, but the bolts by which the crown of the fire box is suspended should also be of equal strength, in order that no discrepancy should exist, and that all parts should be proportioned to a resisting force of 500 lbs. on the square inch.

The next point to be determined by the experiments was, whether the steam of the exploded boiler could have been raised from a pressure of 60 lbs., at which it blew off from the safety valve before it was screwed down, to 300 lbs. in the course of twenty-five minutes. Mr. Ramsbottom instituted some experiments on this subject, from which it appeared, that with the furnace in the ordinary condition, steam in a locomotive