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8 THE CIVIL ENGINEER AND ARCHITECTS JOURNAL [January '•veil, the bottom of which was only 12 feet 0 inches diameter, and as direct proof had been obtained by borings, that below the 34 feet reached in the well, there was a constant recurrence of large springs, giving evidence that the water rapidly increased with the depth, which when 80 feet were obtain ed, became so prodigiously plentiful as to set all temporary means of over coming it at defiance, and precluded ail possibility of having recourse to it for the mere purposes of an experiment, I thought it quite unnecessary .to seek further proof that a sufficient supply for all requisite purposes might with facility be obtained. It would be premature to give, in the present stage of the proceedings, a detailed account of the arrangements I propose making, for augmenting the quantity to an adequate extent, and it may be sufficient to state here that l hare not the slightest doubt, that by sinking a deep well, and extending tun nels, or drifts in the proper direction from its bottom, the necessary supply sill be fully accomplishdd. Being also convinced that the water filtering through the chalk might be considered as entirely divested of all impurities, held in mechanical suspen sion, of which, indeed, there was abuudant ocular demonstration, (as it was so beautifully transparent as to admit of the bottom of the well being seen when the water was upwards of thirty feet deep,) I at once turned my atten tion to the best means of conveying it to London. The principal difficulty which intervenes is the ridge formed by the escarp ment at the outcrop of the plastic and London clays, which Mr. Telford in his proposal to bring the water of the Verulam stream to London, had con templated perforating by a tunnel three and a-lialf miles in length. My con nexion with the London and Birmingham Railway has placed me in posses sion of facts which convince me that at the level at- which Mr. Telford would have traversed some of the beds of the chalk, and the whole of the plasti’c clay, he would have met with very great difficulty, in consequence of water. For this reason, I propose, on leaving the Colne valley, that before entering the ridge which separates it from the district draining into the Brent, the water should he forced to a height of fifty feet above its original level, at which elevation we get rid of the difficulties of the plastic clay, as we only traverse quite its upper extremity, where no water has yet accumulated. The length of the tunnel is also considerably reduced. I have preferred adopting a Line which is materially shorter than Mr: Tel ford’s, as. with the exception of the said tunnel 21- miles in length, no diffi culty of any kind is encountered. Immediately on the water re-issuing into the open air on the side of Brockley Hill, I propose forming a reservoir to contain three days’ supply of water, with a sufficient head to admit of amain being laid hence, and conveyed, (in order to avoid all opposition from land- owners,) from the town of Edgware to Oxford Street, along the side of the road itself ; thereby also facilitating the laying of the main, and rendering all the works of any magnitude, as earthwork, aqueducts, &c. unnecessary. The level of the reservoir will lastly be such, that the highest service can be given; and indeed a part of the town, which none of the present companies can sup ply, will be included within its range. I trust I have now said enough to convince an unbiassed person that there exists no difficulty, both in obtaining a supply of good water from the Springs of the Chalk, near Watford, and in conveying it thence to London. I must, however, impress you here with the necessity of enforcing my arguments, with as numerous a body of facts as can he collected ; and I would therefore recommend that, previously to the meeting of Parliament, I should he autho rised to collect such information respecting the quantity, nature and quality of the wells in every part of the chalk circle which surrounds London, as will bear practically on the subject. This might then be embodied in a second part or appendix to this Report, to be submitted to those who, being unac quainted with geological phenomena, may consequently hesitate in adopting views which others, already scientifically acquainted with the subject, will not ■for a moment call in doubt. In concluding, I may he allowed to cast a retrospective glance at the ad vantages held out by the project I have been called upon to examine. These •then consist in its being proposed to use spring water, already naturally fil tered, in preference to that which has drained a portion of the earth’s sur face ; in making use of that enormous reservoir which nature lias supplied us with in the Chalk, and effecting this at a spot where no existing interests can be injured: and in the selection of such a situation as enables us to convey the supply to London with facility and economy, and at a sufficient elevation to satisfy the demands of even the highest part of the metropolis. I have the honour to be, Gentlemen, Your obedient servant, Robert Stephenson. London, Dec. 1G, 1840. ASSISTANT ENGINES UP INCLINED PLANES. [At the last Meeting of the London and Croydon Railway, the following reports were read, respecting the use of assistant engines up inclined planes.] To the Dire: fore of the London and Croydon Railway. Gentlemen—According to your instructions, I have written to the Liver pool and Manchester, the Grand Junction, and the London and Birmingham Railways, to ascertain whether the practice of assisting trains up inclined planes by an engine at the rear exists on those lines, and whether it lias ever been found to be atcended with danger or inconvenience.—I learn that on the Liverpool and Manchester Railway, the system is in daily use, and that it has never been found to he attended with dangerous consequences ; on the con trary, it is considered safer witli a long train to assist up an inclined plane by an engine behind the train rather than in front.—On the Grand Junction Railway, the assistant engine is behind in assisting up short and steep in clines : but elsewhere the assistant engine, if required for heavy or late trains, takes the lead. Hitherto, neither inconvenience nor danger has resulted from the practice, which is prohibited except on inclined planes.-—On the London and Birmingham Railway. pushing a train on the line is only allowed in cases where the power cannot be applied in any other way. Your obedient servant, Charles 11. Gregory, Resident Engineer. December 8th, 1840. To the Directors of the London and Croydon Railway. Gentlemen.—According to your instructions, I have this day tried an ex periment, in the presence of the Chairman, Deputy-Chairman, and Mr. Baines, for the purpose of determining practically the effect of the assistant engine on the inclined plane at New Cross, and the actual amount of danger to he anti cipated from the sustained pressure of the assistant engine in the case of any sudden stoppage of the train before it. With this view, a train was made up of five loaden coal-wagons of a gross weight of 30| tons ( which is about equal to an ordinary passenger train). The Croydon engine was placed at the head of this train, and drew it up the inclined plane, with the 1 ferrule - engine as sisting at the rear.—On the train acquiring a ve’ocity of 221 miles per hour, the steam of the leading engine was suddenly shut off. The effect was in stantaneously felt in the assistant engine, on which the whole weight of the train seemed thrown hack, causing a strong re-action, which reduced the ve locity of the train to 15 miles per hour, the steam being still acting with full force’ in the assistant engine. The order was then given to stop the assistant engine : the steam was shut off', and the brake screwed down, when the engine instantly separated from the train, and stopped in less than its own length.— The same train was then taken up by the leading engine alone, and on at taining the same speed of 221 miles per hour, the steam was shut off. The velocity of the train was reduced for the first furlong from 221 to 12 or 15 miles per hour, being nearly the same as in the previous case, when the as sistant engine was acting behind. The engine and train stopped in a distance of 7-32nds of a mile, without the use of the brake.—The practical inference from this experiment is valuable, as showing that there is a great deal of unnecessary alarm existing as to the supposed danger of the assistant engine on the inclined plane.—First. Any stoppage of the train is instantly felt on the assistant engine, which may lie stopped before any serious result can arise from its overrunning the train.—Secondly. The effect of any sudden stoppage of the train is to cause such a sudden re-action on the assistant engine that for the first furlong afterwards it appears to communicate scarcely any im pulse to the train, the velocity of the train after the steam is shut*off in the leading engine being nearly the same, with or without the action of the as sistant engine.—Thirdly. The retarding effect of the inclined plane.is so great that the least obstruction would be sufficient to stop the train in r. very slid>fT distance, even when the assistant engine is acting with full force. Your most obedient servant, Charles Hutton Gregory, Resident Engineer. It was stated at the meeting that Mr. M. Ricardo, of Brighton, had con structed a model of a machine which appeared likely to be of use not only in such cases as were now more particularly referrel to, but in cases of collision. —The model was here exhibited. It consisted of a strong frame-work, some what similar to the frame-work of a goods-truck, the area being filled with powerful springs, so arranged as to collapse upon the application of a strong impinging force, the effect of the blow being thus of course broken.—A small experimental railway has been constructed at New Cross station, for the pur pose of testing, as far as a model could test, the efficiency of the invention. THE ORIENTAL STEAMER. Abstract or the Log of the Peninsular and Oriental Steam Navigation Com pany's Steamer Oriental, John Say, Commander, on her second voyage, from England to Alexandria and back. •3 a Falmouth to \ Gibraltar .( Gibraltar to \ Malta .... j Malta to ) Alexandria) Alexandria ) to Malta .. j Malta to \ Gibraltar.. f Gibraltar to \ Falmouth .f Distance in Miles. Hours under Steam. Remarks. [1,029 989 11. M. 143 25 91 0 /Tremendous gales during ( three days. /Fine weather, average speed, "t 11 knots per hour. 827 83 15 Fair weather. 875 93 30 Heavy head sea. 981 103 0 Fair weather. 1,074 118 5 (Heavy gales during three j days. Steamed, out, 2,885.miles, in 317 hours 40 minutes. — home. 2,880 miles, in 314 hours 35 minutes. Total distance, 5,765 miles, in G32 hours 15 minutes. Lowest average rate of speed from Falmouth to Gibraltar, violent gales, 7£ knots per hours. Highest average rate of speed, 11 knots per hour.
