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bered, that the operation was repeated every tide, thus leaving only a short time for the deposition of silt. His experience, therefore, led him to believe, that the outlet-cill should be laid at 6 feet or 8 feet, below the level of the low-water mark, of the lowest spring tides, in order to produce the utmost effect.

The overfall weirs and reservoirs, were, he thought, good precautions, as they materially decreased the necessity for frequently cleansing the drains.

With respect to the question of the separation of navigation from drainage, to whoever the credit of the introduction belonged, there could not be any doubt of the correctness of the principle. He had insisted upon that system, in the drainage of the Middle Level, and it would be there carried into effect to a greater extent than, he believed, in any other district, and he would have an account of the works prepared for the institution.

In that district, in a distance of 30 miles, there was only a rise of 18 inches, so that a level main drain was indispensable.

It was somewhat extraordinary, that there was so little known of the history of the embankment of the river Thames, which, whether examined with respect to its extent or efficiency, was equally remarkable. It was generally attributed to the Romans, and there was every reason to believe, that it was owing to the sound principles upon which the works had been commenced, that they had been enabled to be continued and kept up since in their present state.* It would be observed, that the land on both sides of the river, beyond the bank, was 7 feet. beneath the level of ordinary spring tides, and 10 feet below that of the extra spring tides. The action of the tide had caused the formation of a fore-shore against the banks, which materially assisted them. In short, the embankment of the Thames was, perhaps, the most useful work the Romans had executed in this country, and if they exhibited such a practical knowledge of hydraulic works in one instance, it might be presumed, that they had constructed the Carr dyke, with the intention of its serving as a "catchwater" drain, for which its position evidently fitted it.y

It was not always practicable to establish such drains, but wherever they could be formed, there could be no doubt of their advantage to a system of drainage.

* Vide Dugdale's History of Embanking and Draining; 2nd edition, by Cole (folio; London, 1772); and Cruden's History of Gravesend, p. 23 (royal 8vo; London, 1843.) This latter work contains very good information on these interesting labours of the Romans, and on the present mode of keeping them up.

Mr. J. SMITH (Deanston), was decidedly of opinion, that if it was desirable to place the cill of the outlet sluice 2 feet below lowwater mark, it would be more advantageous to place it as much as 8 feet below. The great point to be attained, was the freedom of discharge, which would be more readily accomplished, by having a considerable column and great cubic section, than by attempting to obtain great velocity. The silting up, would be more completely obviated, by a considerable mass of water, than by the passage of a less stream, at a greater velocity.

The practicability of obtaining a level main drain, must depend, in some degree, on the nature of the district and the height of the surface of the land. There could not be any doubt of the advantage of giving ample depth of water, and it was decidedly preferable to diminish the width, rather than the depth of the upper end of the drain, particularly in very flat districts, where, in an extent of many miles, there was not more than 3 feet, or 4 feet fall, from the upper point to the outlet.

Mr. FAREY said, that the opinion expressed by Mr. Walker accorded, in a remarkable manner, with that of Smeaton, as recorded in some of his unpublished MSS., from which he had extracted the following passages:

Deeping Fen Drainage.

Letter from Mr. Grundy to Mr. Smeaton, dated February 28th, 1770.

"I have taken the levels and surveys; it is a tract of near 40,000 acres, and its uppermost extent, from its proper outfall, near 16 miles, and in breadth 6 miles. Preparatory to forming a scheme for the more perfect drainage of Deeping Fens, near Spalding, I am ordered, by the adventurers of Deeping Fens, to confer with our brother Tofield on the subject matter of draining these fens. As we have made separate reports without any communication with each other, it is no wonder there are some differences in opinion, but one point we cannot reconcile, and therefore have agreed to refer the matter to you. Mr. Tofield recommends digging our drains and rivers to a dead level, or horizontal bottom, from the outfall to the lowest lands to be drained. My opinion, as well as practice is, to form them into one inclined plane, parallel with the mean surface of the country through which they are cut, by which method much expense in digging is saved, and, as I conceive, equally eligible.”

From Mr. Tofield, dated March 8th, 1770.

"I had a conference with your friend Mr. Grundy at Retford, upon the subject of

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the drainage of Deeping Fens, concerning which we had given separate opinions, the principal difference of which consisted in my recommending the mother drain to be carried up, from the outfall, upon a dead level bottom, at least 2 feet below the low-water mark in the Wash, into which it is to issue its water; this Mr. Grundy can by no means approve of, because the 2 feet of water in the bottom, he says, will be dead water, and consequently useless to the drainage; and further, that the expense will be considerably increased. The increase of expense I readily admit, but still strongly contend for the necessity of depth, on account of the smallness of fall, which, according to Mr. Grundy's Report, is not more than 4 feet in upwards of 18 miles; and I further beg leave to dissent from his opinion of such water in the drain as lies below his outfall, being absolutely dead water; however, in order to avoid contention as much as possible, we mutually agreed to beg your opinion of this matter."

Mr. Smeaton's Answer to Messrs. Grundy and Tofield, March 27th, 1770,

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"I think myself much honoured by the reference of my brothers, Grundy and Tofield, in a matter of art. Messrs. Grundy and Tofield both agree that a canal or drain, dug in such manner that its bottom follows the natural slope of the country, and thereby naturally leaks itself towards the lowest point of natural drainage, is dug at less expense than if carried upon a dead level, from the said lowest point; and still less than if the whole canal is dug below the level of the said point; but the question remaining is, as I apprehend it, from both their statements, taken collectively, whether, when so dug, it is not better and more effectual for drainage, especially in some cases.

"The digging of drains, with sloping bottoms, in the manner specified by Mr. Grundy, and for the reasons assigned by him, is undoubtedly the common practice, but where level has been scarce it has been my practice to do them (or propose them to be done) in the manner assigned by Mr. Tofield. A proposition of which sort has occurred, where I have been concerned with Mr. Grundy, and also one with Mr. Tofield. The drains proposed for the country connected with the Foss Dyke,* done by desire of Mr. Ellison, were at least some of them of this kind; but as this scheme was never executed, Mr. Grundy will probably have forgotten this circumstance. The drains for Potterick Carr were also proposed, and in

• Vide Smeaton's Reports, I. 5 (4to, 1762.)

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part executed in this way, which Mr. Tofield cannot but remember, and not only with level bottoms, but proposed to be dug (if my memory does not fail me) 2 feet below the level of the water at the point of delivery.

"A drain may be considered as differing from a pipe only in having, but three sides, instead of four, or the not being compassed all round; and that, however deep the drain may be, like a syphon, it runs to the very bottom. Thus, if a canal was dug on a dead level, 10 miles long, and 10 or (if you please) 50 feet deep of water, and if a quantity of water enters one end, and passes off at the other, over a cascade of a quarter of an inch depth of water, yet the whole body will be in motion from one end to the other. Natural currency of water is in consequence of its falling, or moving from a higher place to a lower, the greater the fall (under equal circumstances) the greater will be the ve locity; and therefore (vice versa) the lesser the velocity given, or required, the less fall is required to produce it.

"In a pipe, it is only necessary, that the end by which the water is to be discharged, be lower than the end by which it enters; for being inclosed on all sides, it cannot escape but by moving forwards, though the pipe itself should be below the level; but in a drain, which is open at top, the upper surface of the water forms a slope, from the upper end of the drain to the lower, which indeed cannot be otherwise, for if you suppose any part depressed too low, the descent being greater (in proportion) to this part than the rest, the water will flow in, till the whole, with the powers respectively acting upon each part, are in equilibrio. principle forms the inclination of the upper surface of running waters in open canals, and that more or less inclined, in each particular part, according as the velocity re'quired is greater or less; which required velocity depends upon the section in the place it holding always true, that an equal quantity must, in the same canal, or pipe, pass in a given time through every section thereof, and consequently, that the velocity will be inversely as the area of the section. (To be concluded in our next biða

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THE GREAT BRITAIN'S" THIRD VOYAGE. The Great Britain, which left Liverpool on the 27th ult., on her third transatlantic

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voyage, did not reach New York till the 15th inst. She appears to have had a narrow escape from shipwreck. We extract the following from the Shipping Report:

"Left Liverpool 4 p.m., 27th September; the first 10 days experienced westerly winds, strong gales, and heavy sea at times, during which the ship behaved admirably. For a few hours of the 2nd of October, the wind was N.E., and in a heavy squall the foremast was carried away. On the 12th, at noon, found the ship had been set 36 miles to the northward in the preceding 24 hours; and on that night found by soundings that the ship again set to the northward 30 miles, from noon of the 12th to 2 a.m. of the 13th; and among the shoals of Nantucket a thick dirty night with very heavy rain; at daylight made signal for a pilot and ran into Vineyard Sound, stopped 10 hours and a half at Holmes' Hole, left it at half-past 2 a.m. of the 14th, and reached Sandy Hook at 11 o'clock p.m., and remained outside for want of water."

The following extract of a letter from one of the passengers, with an inspection of which we have been favoured, adds some interesting particulars.

"Holme's Hole, Martha's Vineyard, Monday, about 8 P.M, Oct. 13, 1845, On board the Great Britain, at anchor. "Here we are, after a voyage so far, which has been most tedious, and not without danger. Fuel nearly exhausted, though we are still 200 miles from New York. Our foremast is gone; three arms also of the propeller, (as the captain informs us,) and all on one side, which last, however, is scarcely credible, as I have not been able to detect any irregularity in the engines, which such a state of things must, I think, have produced. It appears, by the captain's account, that after Saturday a strong current carried us, in spite of his efforts to steer for Block Island, (across St. George's Banks,) right

among the breakers off Nantucket Island; they are called the Rips, and might have proved themselves of the worst kind (of rips) had anything but fine weather accompanied us in our excursion among them. The natives here express their astonishment at our not being wrecked among them, and no doubt the danger has been most imminent. The captain called several of us into his cabin before breakfast this morning, and informed us that he had not coal for more than eighteen hours' steaming; that three arms of the propeller, all on one side, were gone (?), that he was afraid of steaming out to sea, lest any accident should happen to the propeller, and disable him from beating (or clawing) off shore, when a gale might carry him again among the breakers; in which of course, there would be great danger of being wrecked. I should tell you that we had long before this fired guns and hoisted signals for a pilot. We had taken a farmer pilot on board who advised to go round a point within the breakers, on the east of Nantucket I think it must be; but another pilot came off the island and would not carry us through, but advised passing through the Sound, between Martha's Vineyard and Rhode Island, and here we are taking in coal. We had on board at starting, 1050 tons, so that we have consumed about 63 tons per 24 hours. Condenser, 26 in. boiler, 3 in.; cut off at 16in. to 13 generally, making about 13 strokes per minute.

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"Now for the log. (for this see next page.) The last voyage was about 3147 miles; it is sometimes less than 3000, but usually 3100. After leaving Halifax, we must have gone wrong, or soon after. I have no map, but you will find that we must have had a escape soon after leaving Nova Scotia. Two inches had been riveted to each arm before leaving Liverpool, making the disc of the propeller 4 inches more. was a clumsy job, and was, no doubt, the cause of the breakage."

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LIST OF ENGLISH PATENTS GRANTED BETWEEN SEPTEMBER 25 AND OCTOBER 10, 1845. (Concluded from page 288.)

Frederick Harlow, of Paradise-street, Rotherhithe, carpenter, for certain improvements in atmospheric railways. October 10; six months.

Charles Nossiter, of Lyndon End, near Birmingham, for improvements in the manufacture of leather. October 10; six months.

James Hardcastle, of Firwood, Bolton-le-moors, Lancaster, esquire, for certain improvements in the method of conveying water. October 10; six months. Charles Hansom, of Huddersfield, watch-maker, for certain improvements in clocks, watches, or time keepers. October 10; six months.

James Knowles, junior, of Bolton-le-moors, coalmerchant, and Alonzo Buonaparte Woodcock, of Manchester, engineer, for certain improvements in machinery or apparatus to be employed for raising coal or other matters from mines, which improvements are also applicable to raising or lowering men or animals, or other similar purposes. October 10; six months.

William Hodson Greatrix, of Nuneaton, Warwickshire, ribbon weaver, for certain improvements in looms for weaving ribbons and other fabrics. October 10; six months.

James Taylor, of Lochwinnoch, Renfrew, carpet and rug manufacturer, for certain improvements in the manufacture of carpets, rugs and piled fabrics. October 10; six months.

Edmund Barber, of Tring, Herts, decorative painter, for certain improvements in graining and decorating in oil, distemper, and other colours, and in imitating marbles, granites, fancy and other

woods, and in the apparatus and instruments to be used therein. October 11; six months.

Benjamin West, of Saint James's-walk, Clerkenwell, book-binder, for certain improvements in covering or stoppering the tops of bottles, jars, pots, and other similar vessels. October 16; six months.

Stephen Reed, of the town and county of Newcastle upon-Tyne, gent., for certain improvements in railway rails and chairs. October 16; six months.

William Elliott, of Birmingham, button manufacturer, for improvements in the manufacture of buttons. October 16; six months.

John Barsham, of Long Melford, Suffolk, manufacturer of bitumen, for improvements in the manufacture of mattresses, cushions, brushes and brooms, and in machinery for preparing certain materials applicable to such purposes. October 16; six months.

John Marshall, of Southampton-street, Strand, tea dealer, for improvements in preparing cocoa and chocolate. October 16; six months.

William Betts, of Smithfield-bars, distiller, for improvements in the manufacture of brandy, gin, and rum, and other British spirits and compounds. October 16; six months.

James Webster Hall, of Fitzroy-square, gent., for improvements in machinery for cleaning or freeing wool and certain other fibrous materials of burrs and other extraneous substances. October 16; six months.

Hippolite Pierre Francois Desgranges, 1, Skinner's-place, Size-lane, gent., for an improvement or improvements in the mode of manufacturing

corks. (Being a communication.) October 17; six months.

William Henry Stephenson, of Nottingham, merchant, for certain improvements in machinery or apparatus to be used in dyeing or staining. October 17; six months.

Joseph Orsi, of Pimlico, gent., for improvements in sleepers, or blocks for supporting railways. October 23; six months.

Thomas Taylor, of Manchester, cabinet maker, for certain improvements applicable to machinery or apparatus employed for sawing timber. October 23; six months.

Thomas Worsdell, jun., of Stratford, Essex, railway-carriage builder, for certain improvements in apparatus to be attached to and employed in connexion with railway carriages. October 23; six months.

Arthur Smith, of Saint Helen's, manufacturing chemist, for certain improvements in the manufacture of soda ash. October 23; six months.

William Coles Fuller, of Brownlow-street, Holborn, cabinet maker, for improvements in the construction of carriages for railways. October 23; six months. William Thomas, London, merchant, for certain improvements in the construction of umbrellas and parasols. October 24; six months.

William Henry Ritchie, of Lincoln's-inn, Middlesex, gentleman, for improvements in carding engines. (Being a communication from abroad.) Oc

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LONDON: Printed and Published by James Bounsall, at the Mechanics' Magazine Office,
No. 166, Fleet-street.-Sold by A. and W. Galignani, Rue Vivienne, Paris;
Machin and Co., Dublin; and W. C. Campbell and Co,, Hamburgh.

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