During the fine season, which lasts three or four months, the liquid is passed from the fourth house to the boilers, and from thence when it boils to the rope graduating house, where it is repeatedly raised, until the greater part of the salt is deposited upon the ropes, which in very fine weather takes from 12 to 16 hours. In general 27 boilings take 45 days.

The cords are then coated with common salt, so as to be sometimes 0,006 met. (21-3d in.) in diameter; this salt is got off by a cross piece of wood armed with iron plates being raised to the top of the building, and the cords pulled alternately, so as to strike the salt against the plates. In the bad season the water is slowly evaporated in the boilers, of which there are four all of the same size; they are from between 7 and 8 metres long, 5 and 6 broad, and 0.5 met. (19-6 in.) deep.

Yours, &c. Oct. 23, 1831.

H. B. ANDREws.

Garvey's Plan for Ventilating Coal Mines-Sir, In the description you have published in your 431st number, of the pipeing which I propose for the ventitation of coal mines, it should have been stated, that by making the pipes return to the boiler, and the insertion of one being a few inches higher than the other, a constant circulation of hot water would be obtained, on the principle of those used for warming greenhouses, graperies, &c.-Yours, &c., MAURICE (not Michael) GARVEY.

Revolving Houses.-Sir, I called at your office on the day of publication of your 432d No., with an improved plan, which provides against all the objections raised by you, at least as far as human fore sight can. The motion, generally, will not be perceptible. The houses must be locked. An exterior frame also is provided. The inner chambers will not be affected. A revolving house of wood, built firmly, has a better chance of escape than a stone or brick building. Wood is in some measure elastic. The "breadth" of the wind cannot affect the house, the length of the house being opposed only to a space equal to that length. The resistance of the returning stroke can be guarded against by means of springs. A house of wood can be built stronger than is gene. rally supposed; and, if necessary, it would stand a century, revolving, at least, once in an hour at a given rate. Gold and science can cause the blast or hurricane even to pass harmless over the roof,-and a hundred or two would be well laid out in one of the Parks, exemplifying the system.-Yours, &c. MICHAEL ROUGH, Schoolmaster, 21, Little Earl street, Seven dials.

Maps of Cities.-Sir, The plans suggested by Lector, in your Number for the 19th of November, for the improvement of maps of cities, has been adopted in France for at least these fifteen years past, to my recollection, but with the addition of having the squares numbered at the top of the maps, and marked by the letters of the alphabet at the side, and with the further improvement, proposed by F. H., of the list of the streets printed at the sides. This double reference in numbers and letters renders the use of the maps extremely convenient; and I have

one of Paris of that description now in my possassion.-Yours, &c. H., Nov. 30, 1831.

The Tides.-A very remarkable irregularity was observed in the tide of the Hull Dock gates on Sun day week. The moon having entered into her first quarter, gt seven o'clock in the evening of Saturday, it would be high water, by calculation, about noon on the ensuing day; but the tide rose at the old Dock-gates to 15 feet 3 inches on Sunday noon, and continued to flow until a quarter past 2 o'clock in the afternoon, ween it reached 16 feet 4 inches, flowing one inch in the last quarter of an hour; and at twenty minutes to 12, it was again high water there. On Monday afternoon, it was high water at a quarter to two, and on Tuesday morning at halfpast one o'clock. These irregularities in the time of high water arose from the constant north-westerly breezes which prevailed during the previous week.

Zine Sheathing. The Semaphore, a Marseilles paper, states that the ship owners of that place have found the means of rendering zinc, in every respect, equally applicable to copper for covering the bottoms of vessels. By keeping the sheets of zinc in tallow or vegetable grease of any kind, in which is infused about one-tenth portion of verdigrease, all kinds of adhesion on the outside, such as weeds, shells, &c., are said to be prevented. This discovery will, according to the estimate of the French journalist produce a saving to the ship-owners of four-fifths in the expense of sheathing new ships.

INTERIM NOTICES.

We have received a letter from Junius Redivivus, in reply to T. M. B., on Temperance Societies, which makes it proper that we should withhold our own remarks upon the subject, till both can appear at the same time.

Another long Parliamentary Report has reached us on Steam Carriages, of which we shall endeavour to give our readers some account as soon as the abridgement in hand of the one on Steam Navi. gation is completed. We have no doubt of getting through with both long before any practical measure is founded on either.

Many thanks to Scrutator. If he will send to the office on Monday, the 12th instant, the packet will be left out for him.

J. W.'s wishes will be complied with.

We have not overlooked the "other useful Annuals" pointed out to our attention by Ennius; and only wait for a spare corner to bestow a line or two upon them in their turn.

Communications received from Mr. JoplingCaptain White-Mr. Davy-Mr. Ryan-Mr. Laker -T. M. B.-Mr. Fairbairn.-B. C. S.

Errata.-P. 151, col. 2, line 4 from the boltom, for "B=e," read "b-c."

P. 159, col. 1, 1. 18 from the bottom, for "02" read "a2."

LONDON: Published by M. SALMON, at the Mechanics' Magazine Office, Wine-office-court, (between 145 and 146) Fleet Street, where Communications (post paid) are requested to be addressed. Sold by G. G. BENNIS, 55, Rue Neuve, St. Augustin, Paris.

M. SALMON, Printer, Fleet Street.

DESCRIPTIVE ACCOUNT OF THE PRINCIPAL BRIDGES FRECTED OVER THE RIVER THAMES. BY MR. C. DAVY, ARCHITECT.

No. XXI.

The Water-Works.

In my preceding papers under this head I have endeavoured to bring together every thing that could be considered of importance to the professional reader respecting the Old and New London Bridges; but before quitting this locality, it seems proper that I should devote a page or two to the description of the once celebrated appendages to the old bridge- the Water-Works — long esteemed one of the greatest curiosities of this, or perhaps any other country; and, in general, allowed to be superior to those of Marly.

It appears, from undoubted authority, that these works originated, in 1582, with one Peter Maurice, a German engineer, who laid before the Corporation a scheme for supplying the City of London with Thames water. This scheme being approved of, he was allowed, on lease, the use of one arch of the old bridge, and a place on the north side to fix his engine. The duration of his lease was for 500 years, and the yearly rent ten shillings. In the course of two years after he obtained a lease of a second arch. The proprietor and his posterity grew rich, and the public benefitted immensely by the invention Dr. Hughson states, that in the year 1701, they sold the property to Richard Soames, a goldsmith, for £36,000; Maurice having previously obtained another lease of the fourth arch. Soames got from the City a confirmation of Maurice's lease, at the yearly rent of twenty shillings, and a fine of £300; after which, Soames divided the whole property into 300 shares, at £500 each share, and formed a company. It must here be observed, that the vacuities or open spaces for the passage of the stream were not termed archways, but “locks,” bearing the following names:-The first four openings on the north side were called " mill-locks;" then followed in succession the Shore Lock, King's Lock, Little Lock, St. Mary's Lock, Chapel Lock, the Long Entry, Gut Lock, Pedlar's Lock, Fourth Lock, Rock Lock, Se

History of London.

cond Lock, and Shore Lock, adjoining the Surrey shore. The waterway was so contracted by the number of piers and extent of the starlings, that with the exception of the times of high and low water, the fall was found sufficient to turn the immense wheels of the WaterWorks, and effectually to work the powerful engines attached to them. The machinery of which a representation is given in figs. 1 and 2, was designed by Mr. Beighton, and improved by Smeaton. Fig. 1 is a side elevation of the largest engine, taken from the sixth pier of the bridge. For the following explanatory description of these figures I am chiefly indebted to that valuable work, the Pantalogia, vol. iv:-AA, the starlings of the 5th pier, showing the heads of the piles. The water-wheel fills the space between the two starlings as nearly as possible without touching, and the axes of the wheel rest on and turn in plummerblocks, resting also on headstocks DD, supported by the starlings. The waterwheel has four rings EEEE, each having six arms morticed into the axis; each of these rings is provided with 24 starts, e, morticed into it, upon which are firmly secured the float-boards. Upon either end of the main axis are fixed two large wheels (of wood), having on their periphery a ring of iron cogs, fixed on in segments. These wheels G take into two trundles, and by connecting-rods H, and cranks, form the communication to the beams I, which are connected at their other ends to the pump-rods. There are six pumps, beams, &c., three on each side of the water-wheel (only one set are exhibited in the drawings). It will be seen that the beams or regulators (as they are sometimes called) are arched at one extremity, upon which the chains attached to the piston-rods are laid MNO. The joints of the crank-rods, f, g, h, are screwed together round the crank neck, and furnished with brasses in the usual way; the connecting-rods have each a circular flange in the centre, held together by four screws. These screws being removed, the connecting-rod is then divided, and the pistons may be drawn completely out of their cylinders, for the purpose of any repairs that may be required. Each pump-rod has a crosspiece, o, fixed on the top of it, to which the two outside chains are screwed, and the lower ends of the same chain are

fastened to the lower end of the arch. These chains act to push down the pistonrods; the other two chains which raise the rods are fastened to the top of the arch, and to the rods at the lower ends, as shown in the beam . The action of the pumps (which are forcing pumps) do not differ from those generally known. When the solid pistons are drawn up, a vacuum is formed in the cylinders, and the pressure of the atmosphere on the surface of the water (from which the pipe Q draws) raises the valves at the bottom of the cylinders, and fills them. At the descent of the buckets the lower valves shut, and the water contained in the cylinders can find no passage but through the valves in the pipe R. The cranks are so arranged, that a constant succession or stream of water is kept up the pipe; R is the outlet or main communicating with the streets. The engines were calculated by Desaguliers to supply the enormous quantity of 1954 hogsheads in an hour to the height of 120 feet, including the waste, allowed to be one-fifth of the whole.

(To be continued.)

THE RIGHTS OF INDUSTRY.† When about this time last year, the breaking and burning of machines was a favourite scheme with the ignorant rustics of the south of England, for bringing about high wages and cheap bread, the Society for the Diffusion of Useful Knowledge, produced a seasonable little work, in which "The Results of Machinery" were very ably shown to be all in favour of those, who had thus insanely banded together for its destruction. This year, the discontent of the labouring poor is supposed to threaten a different sort of outbreaking-that of a war against accumulated property of every description-and to stay the progress of this new variety of popular distemper, the Society have come forth with another small treatise, by the same author, which has for its object to show that the right of property is but a con

See also Switzer's Universal System.

The Rights of Industry, addressed to the Working Men of the United Kingdom. By the Author of "The Results of Machinery." Section I. Capital and Labour. Forming one of the numbers of the Working Man's Companion, published under the Superintendence of the Society for the Diffusion of Useful Knowledge.

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as

vertible term for the right of every man to retain and enjoy the fruits of his own labour; and that it is, therefore, much the interest of the poor as of the rich, that it should be held inviolable. We must confess we entertain very strong doubts of the reality of the danger which has given birth to this treatise of the "Rights of Industry;" and as the assumption is of a nature that seriously affects the character of the working classes of England, we must, before speaking of the merits of the book itself, take leave to request attention to the Society's statement of the grounds on which that assumption rests. The Society are supposed, in the following extracts, to be addressing themselves to the "working men of these kingdoms:"

"Pretended Rights' are held up to your wondering credulity which a little honest and patient consideration will show to be the greatest Wrongs' that could be inflicted on yourselves, and on every other class of society if they could be called into action. Sometimes these doctrines meet you in the violent addresses that wrong-headed men deliver in popular assemblies. Sometimes they force themselves upon your notice in the shape of miserable writings, which profess to advocate your interests against those who are called your oppressors,-by which name all those are meant who have any thing to lose, and anything to defend. Sometimes they are proclaimed aloud from Rotundas,' where the priest of Atheism and the orator of Plunder stand side by side. And, lastly, they insinuate themselves to your view, scattered amongst sound principles, intended to explain to you the laws which govern the production of wealth, in lectures on Popular Political Economy." One and all of these counsellors, we say, are your bitterest enemies. They would lead you away from the pursuit of those means which can alone better your condition, to the cherishing of vain delusions, which will make you first unhappy, then idle, then starving, and then utterly depraved and worthless. Such doctrines may begin in the lecture-room, and there look harmless as abstract propositions ; but they end in the maddening passion, the drunken phrenzy, the unappeaseable tumult, the plunder, the fire, the blood -of such scenes as have just disgraced our country, and made one city, amongst the earliest in the march of civilization, a bye-word and a reproach for all the civilized earth.

66

"It may perhaps be said that the doc

trines which are thus advocated do not lead to pulling down and firing houses. The advocates of the doctrines do not want a destruction of property; they only request a division of it. Say what they will, the doctrines distinctly tend to establish disorder; and if the reign of disorder is allowed to exist, you will instantly cease to be producers, and as instantly be deprived of the power of being consumers. The course of national misery resulting from national disorders always begins with financial embarrassment, by the destruction of capital, or its withdrawal from all useful works. Those who would advise the "division of property" by force or fraud, say, "to taik of sending away roads, bridges, canals, and cultivated fields, is a striking absurdity." They do not say that the roads and bridges and canals would cease to be used, and the fields would cease to be cultivated, when the capital was gone. Capital was circulated only because it could be circulated with security. If the present capitalists were driven away, as these reasoners would imply might easily be done, and the labourers were left to work the tools and steam-engines-to labour in the manufactories, and to inhabit the houses of the present capitalists,production could not go on an hour, unless the appropriation of the plunder were secured to the individual plunderers. We cannot exactly see the course of the operation; but we think that the advo cates of the principle may discover a new historical fact, for an illustration of its practical working, in the riots at Bristol.

"The advocates of the division of property have, however, some inen amongst them who are more temperate in its distribution, than those who burn houses that they may carry off featherbeds. The scheme of these philosophers is, at the death of any member of the community, to abolish the exclusive claim of his widow and children, and to divide his property among all the members of society who have just arrived at adult aget." It is not necessary for us to argue as to the justice or injustice of this proposition; for we have no hesitation in affirming that if such a distribution were to take place, there would be no property to distribute."

Again, after quoting a very excellent passage in support of the right of property, from Cooper's Lectures on the

Hodgskin's Popular Political Economy.

+ Free Enquirer, published at New York, 1830.

Elements of Political Economy (an Ame rican work):

"These are not the words of some advocate of arbitrary government—some upholder of exclusive privileges-some courtly admirer of lavish expenditure. They are the words of a stern republican, teaching the American youth the sound doctrines of political economy, and teaching them at the same time some tenets of government which would be thought much too strong for utterance under a monarchy, and, indeed, would be unsuited to our actual condition. But, lover as he is of a purely democratic form of government, he never thinks that a supreme power residing in the people is to involve the destruction of the rights of property. He knows that to destroy the right of property is to destroy the power of the people to produce, and he wisely and honestly tells them so. Not so the class of teachers whose new theories for advancing the prosperity of mankind in general we have exhibited to you. • In asserting that accumulation of capital,' says Mr. Hodgskin, 'in the hands of persons who neither make nor use it, impedes the progress of society, let me not be supposed to overlook the statement, that if there were no profit to be obtained on the capitalist's stock, there would be no motive to save, no spur to industry, and no increase of national wealth. I do not overlook this statement; but because I am sensible of its importance, I will not hastily and dogmatically decide concerning it.' We have seen how Mr. Hodgskin has decided. This is the candour of the cruel and despotic judge, who says to a prisoner, Let me not be supposed to overlook the evidence of your innocence. I do not overlook this evidence but, because I am sensible of its importance, I will not hastily and dogmatically decide concerning it, but I will only say that you shall be taken hence to the place whence you came, and thence to the place of execution.' Surely, the working-men of this country are not to be deceived by such feeble, and at the same time presumptuous reasoners!

"To you who have patiently borne with us in our examination of the great questions upon which this little book so imperfectly treats, it is, we should think, unnecessary to urge the paramount duty of exhibiting, during a time of strong political excitement, a respect for the laws, and a determination to maintain the private rights of all men inviolate. The rights which are most open to attack, as we have shown you, from designing and ignorant persons, are the rights of pro