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either supersede, in many cases, the employment of steam, or lend a powerful aid to this mighty instrument in all the operations in which it is at present employed. The carriage was impelled along the railway about a mile and a half, and travelled at the rate of upwards of four miles an hour, a rate which might be increased by giving greater power to the batteries, and enlarging the diameter of the wheels. We understand that the carriage was built at the expense of the Railway Company, and we cannot but congratulate them in having the discernment to employ Mr. Davidson, a gentleman of much practical knowledge and talent, to whose genius great discoveries have been made in electro-magnetism, by whom the carriage was projected, and to whose unwearied exertions the practicability of the scheme is almost placed beyond a doubt.

The dimensions of the carriage are 16 feet long by 7 feet wide, and is propelled by eight powerful electro-magnets. The carriage is supported by four wheels of 3 feet diameter. On each of the two axles there is a wooden cylinder, on which are fastened three bars of iron at equal distances from each other, and extending from end to end of the cylinder. On each side of the cylinder, and resting on the carriage, there are two powerful electro-magnets. When the first bar on the cylinder has passed the faces of two of these magnets, the current of gal. vanism is then let on to the other two magnets. They immediately pull the second bar until it comes opposite them. The current is then cut off from these two magnets, and is let on to the other two. Again they pull the third bar until it comes opposite, and so on—the current of galvanism being always cut off from the one pair of magnets when it is let on to the other.

The manner in which the current is cut off and let on is simply thus :—At each end of the axles there is a small wooden cylinder, one-half of which is covered by a hoop of copper; the other is divided alternately with copper and wood (three parts of wood and three of copper.) One end of the coil of wire which surrounds the four electro-magnets, presses on one of these cylinders, on the part which is divided with copper and wood; the other end of the coil presses on the other cylinder in the same manner. One end of the wires or conductors which comes from the battery, presses constantly on the undivided part of the copper on each cylinder. When one of the iron bars on the wooden cylinder has passed the faces of two magnets, the current of galvanism is let on to the other two magnets, by one end of the coil which surrounds the magnets, passing from the wood to the copper, and thereby

forming a connexion with the battery. This wire continues to press on the copper until the iron bar has come opposite the faces of the two magnets, which were thus charged with galvanism. On its coming into that position, the current is cut off from these two magnets, by the wire or rod of copper passing from the copper to the wood, and thereby breaking the connexion with the battery. But when the wire or rod of copper leaves the copper on the one cylinder, it leaves the wood, and passes to the copper on the other cylinder at the other end of the axle, and in so doing connects the other two magnets with the battery, and they pull the next iron bar in the same manner. At the other end of the carriage there are other four magnets, and wooden cylinder, with iron bars arranged in the same manner.

The battery which is used for propelling the machine is composed of iron and zinc plates immersed in dilute sulphuric acid, the iron plates being fluted so as to expose greater surface in the same space.

The weight propelled was about six tons.

[We are glad to see that the value of the electro-magnetic agency, as a moving power, is at length likely to have a fair trial. The plan of Mr. Davidson is precisely the same as that of

Captain Taylor, described in vol. xxxii. page 694; but it will no doubt be in the recollection of our readers, that Mr. Davidson claims to have adopted that plan before it was patented by Captain Taylor. See Mech. Mag. vol. 33, pp. 53, 92.-Ed. M. M.]

INSTITUTION OF CIVIL ENGINEERS.

June 28, 1842. “ An Account of the Bridge over the

Thames, at Kingston, Surrey." Ву John Brannis Birch, Grad. Inst. C.E.

Previous to the year 1828, when the present bridge was opened to the public, the communication between the town of Kingston-upon-Thames in Surrey, and the hamlet of Hampton-wick in Middlesex, was carried on by an old and incommodious wooden bridge, which was so dilapidated that any attempt to put it into a substantial condition for the service of the public, would have been equivalent to an entire rebuilding of the structure.

The corporation of Kingston, therefore, resolved upon erecting a new bridge, on a design by Mr. Lapidge, their architect, and in the year 1825 obtained an Act of Parlia. ment, granting them the powers necessary for that purpose.

The trustees appointed under the Act applied to the Exchequer Bill Loan Commis

sioners for pecuniary assistance to the On the completion, Mr. Telford again amount of £45,000, but the application made a report to the Exchequer Bill Loan was not entertained until the working draw, Commissioners in these terms:-“With Mr. ings, specification, &c. had been submitted Lapidge, I examined the whole of the bridge to their engineer,--the late Mr. Telford, and approaches, and taking it for granted when he gave the following opinion : that the foundations of the piers and abut. “Having carefully inspected all the work. ments, which are under water, and which I ing drawings, I consider it only justice to had no opportunity of inspecting while in Mr. Lapidge to say, that they are very com progress, are according to the working draw. plete and do credit to his judgment and assi ings, all the other parts are found in a very duity; and as the blue clay has been found perfect state, executed in a workman-like quite across the bed of the river, I am of

manner." opinion that, with the precautions provided The bridge has in every respect answered in the working drawings and specification, the object for which it was intended, and it the work is very practicable, and if well has justified the good opinion Mr. Telford executed will prove a substantial and useful originally formed of it. edifice." He also said, “I have gone During the fourteen years which have through the detailed estimates, and com elapsed since its erection, it has required pared the same with the proposal accepted none other than the most trifling repairs, and by the corporation, and am satisfied bat the expectations of the trustees have been the works may be properly executed for the realized By the tolls having paid the allotted sum therein mentioned, viz., £31,300 ;”. portion of the principal, up to the present and he stated “the amount of the general time, as well as the interest of the money estimate including the above sum-the ex borrowed for its execution, and the cost of it penses of houses and ground—the flood did not exceed the amount of the estimate. arches and roads of approach, &c. to be The communication was accompanied by £47,457.

seven remarkably well-executed drawings, Upon receipt of this report, the Commis showing accurately all the details of the consioners consented to make the required loan, struction, and the Paper contained all the but it being found that the Act limited the quantities of materials in the work, together amount to be raised to £40,000, alterations with Mr. Telford's reports upon it, with in the structure were suggested by Mr. other documents of interest. Lapidge, which received Mr. Telford's approval, and the works were commenced on Description of the Harbour of Port Tal. the reduced scale.

bot (Glamoryanshire).By Henry Ro. The bridge is of Grecian architecture and binson Palmer, V. P. Inst. C. E. consists of five elliptical arches ; it is con The harbour described in this communi. structed chiefly of brick, with ashlar facing. cation is situated upon the outfall of the The abutments are terminated by towers, river Avon, on the eastern shore of Swansea and the structure is surmounted by a cornice Bay. The adjacent mountainous district and balustrade, with galleries projecting over terminates abruptly at about half a mile the piers. The span of the centre arch is from the shore, in a tract of marshy land, for 60 feet, with a versed sine of 19 feet; the most part composed of sand, with deside arches are 56 feet and 52 feet span, and tached beds of clay and peat of various thick. 18 feet 3 inches and 16 feet 6 inches rise, ness, at about 10 feet below the surface. respectively. The highest food rises 6 feet The river, which, at its issue from its above the springing line, and the lowest rocky channel, had been diverted from its summer level is about the same distance

course by accumulations of sand, nearly at below it. The foundations are all laid upon right angles with its point of discharge into the substratum of blue clay. The length of the sea, would appear at some period to the bridge is 382 feet to the extremes of the have had a direct channel thither. It has abutments, and the width between the balus been the object of the author, by whom the trades is 25 feet. The proportion of the works were designed and executed, to repiers to the span of the arches is about gth. store this obvious course for the land water, The roadway is formed at an inclination of and by means of embankments, to convert 1 in 40.

into a dock that portion of the old channel The author then describes fully the con which extends through the marshes. A new struction of the abutments, piers, arches, channel has also been formed from the outand the superstructure. The work occupied fall to a convenient part of the dock, with a about 2 years to the completion, the first lock 45 feet in width for the passage of yesstone having been laid on the 7th of Novem sels. ber, 1825, and the bridge opened in form on As the works were undertaken by a few the 17th of July, 1828.

private individuals, every proper economy

the

WATER

QUESTION

was enjoined ; and in order to diminish THE

UNFILTERED the expense of excavating by manual labour a WATER DELETERIOUS TO HEALTH AND channel of 100 feet wide and a mile in length, DESTRUCTIVE TO LIFE, Mr. John Vigurs (whose extensive tin-plate Sir,-I propose

to

prove, and copper works are situated in the ad.

First, that impure water is injurious to joining valley) proposed that the new chan

health and life; and, nel should be formed by the force of the

Secondly, that the water, particularly, land floods, which descend with great impe

supplied by the water monopolies of London tuosity. A trench of 20 feet wide by 10 feet

is impure, and, at the present season, from deep, was therefore cut in the line of the

the fall and decomposition of vegetable matproposed channel; and a few days after it

ter, a primary cause of the augmenting mor. was finished, a heavy land flood descending

tality of the metropolis. from the mountains rushed through it, car First. To prove this department of my rying out to sea from the sides and bottom of the trench an immense quantity of the

case, I call

Hippocrates, the Father of Medicine, who soil. Every succeeding flood increased the

says, “ To distinguish that water which is size of the trench, and by judicious guidance wholesome is of the first importance to of this natural excavator, the channel was

health, for a train of evils are the conseformed of the requisite dimensions; and it is

quence of the use of bad water." now generally kept clear from accumulation

Dr. Griffiths.

.-" With regard to the water by the land floods, but in dry seasons by the

in use, we cannot be too scrupulous ; the sluices in the lock-gates. The bed of the

purity of this element being almost of equal channel is stated to form a regular inclined

importance to us with the air we breathe.plane of more than a mile in length, free

Dr. F. Hoffman.—“ If every physician from a shoal or any other impediment. would make it his practice carefully to exa.

The confluence of the two channels has been rendered permanent, by a pier of cop

mine into the quality of the water used in

the houses he visits, he might confidently per slag, with an active slope of five to one. When finished, this pier will extend full half

hope to practise with more benefit to his a'mile in length.

patients."

Dr. Mead, after speaking of poisonous The paper then describes generally the

exhalations and airs, observes, that impure ordinary modes of construction adopted in water “must be necessarily almost equally the works, and more particularly the lock, fatal and dangerous.He adds,

a late the cill of which is 23 feet below the level

authority, by searching into the first accounts of an ordinary spring tide : the coping is 2

of the scurvy, finds that the origin of it was, feet above that level, and the gates are 25 in all times and places, charged upon the feet 6 inches high.

use of unwholesome water." The fabric of the lock is composed of hard Dr. Lind ascribes the scurvy (inter alia) silicious sandstone, cemented with blue lias

to those " who are obliged to drink unwhole. lime mortar. The ashlar work of the walls

some water." is 4 feet in thickness, with counterforts, and

Dr. Harrison.—" The dry rot in sheep the spaces between them are filled with rub.

has its cause in the poisonous residuum of ble, grouted with lime and sand. The whole

water. A flock of sheep will rot in one thickness of the walls may therefore be taken at 8 feet, excepting at their bases,

day; or, on some water meadows, when the

weather is sultry, in half an hour." where they are 10 feet. The walls rest in

M. Cabanis.—“ Water loaded with putrid part upon an inverted arch, three feet in

vegetable matters, or with earthy substances, thickness, and the whole mass, including the

acts in a very pernicious manner on the stoinvert, rests upon a concrete of large and

mach, and the other organs of digestion ; small rubble.

producing different kinds of diseases, both The harbour is stated to be in immediate

acute and chronical *

* they blunt the connexion with extensive copper and tin

sensibility, enervate the muscular force, and plate works, and also with a great extent of

dispose to all cold and slow diseases." coal-beds bordering the valley of the Avon, Dr. W. Lambe.—" It is the putrescent and the trade is rapidly increasing, its posi matter which is the most noxious principle tion in the Bristol Channel being highly

of common water

* sometimes the favourable to a foreign trade.

stomach feels as it would burst ; someA plan of the harbour, with the streams

times the sensation is, as if a cord were tied and channels, and a transverse section of the

round the middle of the body.lock accompanied the paper.

The peculiar noxious principle of bad
water nothing but the corrupted animal
and vegetable matters with which they are

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who say

impregnated ; these matters are, therefore, Sir John Hall.-" Have you any observa. poisonous.

tion to make on the state of the water?" (What must the water be into which the (St. Katharine's Docks.) common sewers of upwards of a million of I came to the docks, and found the human beings pour their filth daily?)

water very impure, and could not use it : Dr. Ure." It cannot but be an interest. the clothes that were washed in it were dyed, ing object to ascertain the component parts and made of a bad colour." and qualities of the water aily consumed “ Can you use it for culinary purposes?" by the inhabitants of large cities. A very “ No; not without filtering.' minute portion of unwholesome water, daily Dr. Paris.-" My opinion, as a physitaken, may constitute the principal cause of cian, is, that the water (Thames water) is the differences in salubrity which are observ. injurious to health. I visited a family who able in different places."

were all ill, in the autumn, and I believe Mr. Abernethy.--" Diseases have been their illness arose from drinking the water excited by water, and therefore it is neces on coming to town; they changed the sary that whatever is used should be as pure water, and drank other water, and got as possible."

well.'

As a physician, who Sir Henry Halford and Lord Wharncliffe. has devoted much attention to the subject, I

A constant supply of pure and whole cannot find terms sufficiently expressive of some water is essential to the health and the quful effects it may be likely to produce comfort of the inhabitants of this great and upon the health, and even lives of the in. thickly-peopled metropolis."

habitants." I trust the above witnesses will be held Dr. Yeates.-" I should say of this water, sufficient to establish my first proposition ; that it is not wholesome : I mean the ob. and I now, therefore, proceed to my second, servation to apply to any Thames water in in order to fasten these evils upon the right and about London." shoulders, to wit, the water monopolists of Dr. W. Somerville.--" It seems to me London.

that the question of the purity of the water Dr. James Johnson.-Question-" Have has been placed on a very erroneous footing you, in your practice, met with any injurious

by many,

that there is no ingredient effects from the use of Thames water?" in the water in London to produce disease :

Answer" Yes; I was informed by Mr. this reasoning would equally apply to water Ibell, Waterloo-place, who has a great many taken from the pan of a water-closet." young women employed in the millinery bu. Dr. Hooper.-" The daily use of impure siness, that several of the young people have water (speaking of the water supplied by one been repeatedly affected with bowel com. of the Companies) has a tendency to proplaints ; but that if they went out of town a duce or is the cause of many diseases, and few days, and drank other water, the complaint it is a question of much importance whether subsided, but often returned again on their such matters in the stomach do not greatly again drinking this water. I am the medical contribute to the production of that state of attendant on this establishment."

faulty digestion and impurity of blood, of Mr. William Ibell.—“ Have you reason which the inbabitants of this and other large to think that the health of any of your family cities are constantly complaining." has been injured by the use of this water? Mr. Keate.—"By the aid of filtering Most assuredly. In what way? Rather machines, and a steam kitchen, I endeavour progressively. I employ a number of females to avert from my family the mischiefs and in my business, who are from the country, dangers which I should otherwise apprehend and they are frequently affected, and also from the use of the sad compound (Thames my family in general; they appear at first water) which is laid into my house." pallid, and- then headache comes on, and The Medico-Chirurgical Review, vol. iv. they become affected in their bowels; I have p. 207.-"A time must come when the had seven or eight at a time thus affected ; people of London will open their eyes to this when it has been so for two or three days, I scene of corruption, veiled and concealed as then change the water to pump water, and it is by iron tubes and stone pavements. in less than three days the effect is gone. It We are not among the idolaters of the was the same when I resided in the city, and ancients; but we do admire the delicacy of there it was I first discovered the cause to be their taste, in expending so much labour and in the water; and that time I used the wealth in commanding abundant supplies of New River water. So that the same pro. pure and salubrious water for the Everlastportion of effect was produced from the use ing City.' of the New River water, as from the use of Mr. William Clapp," All sorts of im. the Thames water? Yes, nearly so; but the purities are found in the Thames water ; in water of the New River is not so full of my opinion as a professional man, the water fibres as that of the Thames,

ABSTRACTS OF SPECIFICATIONS OF ENGLISH

is decidedly impure and injurious; hurtful called for by the unanimous voice of the in the extreme.''

various organs of public opinion ? The Royal Commissioners, Dr. Roget,

I have the honour to be, Sir, W. T. Brande, and Thomas Telford.

Your obedient servant, We have endeavoured to gain information

B. from various sources, respecting the state Grafton-street, Sept. 26, 1842. and purity of the Thames water, and its general fitness for domestic use; and from such inquiries it appears proved to us, that the quality of the water within certain limits,

PATENTS RECENTLY ENROLLED. included in what may be called the London THOMAS RUSSELL CRAMPTON, OF SOUTH. district, has suffered a gradual deterioration

WARK-SQUARE, ENGINEER, AND JOHN within the last ten or twelve years. We

Coope HADDAN, OF LIVERPOOL-STREET, found this opinion upon the well-ascertained SAINT PANCRAS, CIVIL ENGINEERS, for fact of the disappearance of fish from those

certain improvements in steam-engines and parts of the river, to such an extent as to

railway carriages. Patent dated, February have led to the almost entire destruction of 15, 1842. the fisherman's trade between Putney Bridge These improvements comprise, first, an and Greenwich ; and upon the circumstance improved method of reversing, and varying that the eels imported from Holland can or altering the cut off of the steam, by varynow with great difficulty be kept alive in

ing the position or inclination of one eccenthose parts of the Thames where they were tric rod to each cylinder of locomotive, staformerly preserved in perfect health. We

tionary, and marine steam-engines ; second, also learn that the fishmongers in London an improved method of altering the lead of find it impossible to preserve live

fish for any admission, by giving various inclinations to length of time in water from the same dis the valve-rods of locomotive, stationary, and trict."

marine steam-engines ; third, an improved Dr. Bostock.-" It appears that the water method of cutting off and of varying the lead of the Thames, as it approaches the metro of admission, (without increasing or dimi. polis, becomes loaded with a quantity of filth nishing the traverse of the slide-valve,) by which renders it disgusting to the senses, varying the inclinations of the eccentric rods and improper to be employed in the prepara of locomotive steam-engines; fourth, a metion of food." *

“ Two bottles

thod of diminishing the friction of the slide. were sent to me for inspection, one contain valves of locomotive, stationary, and marine ing the water of the Thames, the other con. steam-engines, by the application of imtaining water taken from the same source proved pistons to such slide-valves ; fifth, after having been filtered : the former exhi.

an improved method of regulating or alterbited the usual appearance, while the latter ing the admission of steam, in its passage was perfectly free from visible impurities, from the slide-valve box to the inside of the and had lost all unpleasant flavour or odour. cylinder of locomotive, stationary, and maI think, therefore, we may conclude that

rine steam-engines, independent of the action the process of filtration, if properly con of the slide-valves; sixth, an improved meducted, would be in all respects unexcep thod of using steam expansively in locomo. tionable, provided a sufficient quantity of tive steam-engines, by increasing the size of water could be procured by this means for the cylinder, and applying a regulator, or the supply of the metropolis.”

throttle-valve, to each cylinder; seventh, a Surely it is unnecessary to crowd your method of lowering the centre of gravity of columns with additional proofs of my second locomotive steam-engines, by improved arposition, hence I shall not make extracts rangements and combinations of the various from the evidence of Dr. Brodie, Dr.

parts ; eighth, an improved method of conTurner, Dr. Hume, Dr. Macmichael, Dr. structing the tubular boilers of locomotive Bree, Mr. Thomas, the President of the steam-engines, by lowering the position of College of Surgeons, &c. I have struck the tubes, and applying a bridge across the out many unnecessary words in the extracts fire-box; ninth, the application to locomoI have given, in order to save the space of tive steam-engines and railway carriages of your Journal, and the time of your readers. cylindrical wheels, with outside flanches Í therefore conclude with the following, not fitted to axles which will allow each wheel impertinent inquiry: Why is it that in the

to run independent of the other ; tenth, the increasing mortality which the recent weekly affording additional security to locomotive bills exhibit, the remedy Dr. Bostock sug.

steam-engines, by the addition thereto of gests, and which it was stated in the House

extra (safety) wheels or sledges ; eleventh, of Lords, could be at once supplied, is not the application to railway carriages of springs

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