Let AI (fig. 3) represent the plane on which the following given forces, viz. B=6, C=7, D=3, and E=9, act upwards on the points F, G, H, and I, at the several distances from the end A of 5, 6, 16, and 32 inches, and let the downward forces be K=5, L=16, and M=4, acting on the points N, O, and P, at the several distances from the same point A of 8, 18, and 20 inches. Now it is evident there are

18

M

still two conditions to be observed 1st. Whether the sum of the upward be equal to that of the downward weights, (which may be found by addition,) for were the weights alone to be considered, they would be in equilibrium. 2nd. Whether the weights act in their proper places, which is to be found by the same rule as before; thus taking the upward forces.

L M

And since they are in equilibrium they destroy the effects of each other, and the plane will be at rest.

There is one more case to be attended to.

Fig. 4.

E

Let AD (fig. 4) represent a plane, on which act the two unequal forces or weights C and E, in opposite directions, and of which E is the greater.

1

16 x 182 88

4 X 20-80-408.

It is required to find the place and weight of a single force that will produce equilibrium. Now from what has been previously stated, the required force will be equal to the difference of those which are given, viz. E-C. With regard to its place, it has been shown that two forces will keep a single force in equilibrium if one force bear the same proportion to the other, as the distance between the opposite weight and the single weight. Now supposing the distance between the points A and B to be expressed by the letter e, this proportion will stand thus —(E—C)·.·C::e: the distance between the point B and that on which the weight (E-C) acts, and which distance may be called d. But if the weights C and E be known, then the other parts may be also discovered (provided the distance between them be also given). Let the weights C=3

and E=7, then E-C=(7–3)=4, which will be the weight required, and let the distance e=8 inches, then the proportion will be as 4:3::8:6, which will be the value of d, and consequently be the distance from the point B, that the required weight F=4, must be to keep the other weights in equilibrium.

In the last case these given forces were unequal. Now it can be proved that the nearer they approach to equality, the further will be the distance of the required force, until they are exactly equal, when the distance will be infinite. Thus supposing the weight C to be equal to 6, then the proportion will stand thus. As EC:C::e:d, or as (7-6)=1:6::8:48, which would be the distance of the required weight from B; but suppose the difference to be still less, viz. A=6, it will be then as (7-6%)

:68:552, the distance required, and which will keep on decreasing until the weights are equal, when it will be as (7-7)=0:7::8:0 or infinity, when there will be no weight required, and from which this conclusion may be drawn, that if there are two equal weights acting on the same point, and in opposite but parallel directions, they will not admit of any counterpoising weight; and this may be said to be the spirit or doctrine of statical science.

(To be continued.)

was

were boiled in water, until no further quantity of carbonic acid was disengaged. This hot solution gradually mixed with the first, continually agitating until effervescence ceased; an abundant dull yellowish green precipitate was formed. About three parts of acetic acid were then added, or such a quantity, that a slight excess was sensible to the smell; gradually the precipitate diminished in volume, and in some hours a slightly crystalline powder was deposited at the bottom of an entirely colourless solution. The fluid was poured off as soon as possible; and the powder, washed with plenty of boiling water to remove the last portions of arsenic, was then of a

brilliant colour.

In

Care must be taken not to add to the cupreous solution an excess of arseniate of potash, as it causes waste of the acetic acid afterwards added, as the latter must be in excess. repeating the process in the large way, an arseniate of potash, prepared with eight parts of oxide of arsenic, instead of six, was used, and the result was very successful. M. Braconnot thinks that probably a slight variation of the advantageous; but in the mean time proportions he has given may be found he considers it right to give the best process he is able for the preparation of a colour so beautiful, and which may be very valuable in the arts.

THE SECRET OF THE COMPOSITION OF THE SCHWEINFURT BLUE.

A portion of a very fine blue pigment was placed in the hands of M. Braconnot, by M. Noel, for examination. It was the produce of a manufacture at Schweinfurt, where the preparation was kept secret. M. Braconnot readily ascertained it to be a triple compound of arsenious acid, hydrated deutoxide of copper, and acetic acid; so that it approximates to the green of Scheele. After various trials to form it, the following process was found to be the best. Six parts of sulphate of copper were dissolved in a small quantity of water; also, six parts of white arsenic, with eight parts of potash of commerce,

CHINESE SUBSTITUTE FOR CANAL-LOCKS.

(From the Boston Journal of Science.) It has been observed, that locks were unknown to the ancients; they are still unknown to the Chinese. Some of the canals of China, however, are constructed on different levels, and their method of passing boats from one level to another is worthy of attention. The levels are connected by inclined planes, constructed of hewn stone; these inclined planes, in some instances, connect levels differing 15 feet in elevation. In passing from the upper to the lower canal, the boat is raised out of the water, and launched over the inclined plane; the last part of the operation, of course, requiring no great labour, as the friction over the plane retards the descent of

the boat: but in passing from the inferior to the superior canal, powerful engines are required. These consist of capstans, from which ropes are passed round the stern of the boat. The effort of a hundred men is sometimes required to effect the elevation of a loaded boat. The objection to this mode, taken in this simple and rude form, lies not only in the great labour required by it, but in the injury which must necessarily be done to the boats. The practice could never be adopted with the slightly-timbered barges used in our canals, which are calculated to be supported by the fluid in which they move, and which presses with a force perfectly equal on every part with which it is in contact. There are some situations, however, where, from a scarcity of water, the inclined plane is necessarily substituted for the lock. Some works of this kind are used on the Continent of Europe; and in England, in some cases where the weight of the descending greatly exceeds that of the ascending commodities-as in the traffic between mines and 'furnaces-inclined planes are used with advantage. In these situations, the descending and loaded boat is made to drag up an ascending one, which is empty, or but lightly loaded; thus exhausting in a useful purpose a force which not being expended in friction, as rollers or wheels are used between the boat and the plane, could not be otherwise controlled without some labour and cost.

way:

191

"The entire line of the railway is in steady progress to completion, with as much order as any undertaking of similar magnitude can be conducted." Ohio is, as your readers are aware, one of the back states; and as railways are already laid down throughout the United States, your readers have to complain not that you are arousing the public to this subject, but that the United States have taken the lead. Your correspondent "B" will perceive that you are labouring to prevent the United States from wresting from us our cominercial and (I may add) maritine superiority, and that Liverpool and Manchester are but acting in self-defence.

I am, Sir, your obliged servant,

T. Νου. 2. Mr. Editor, With respect to the proposition of "W. B." in your Magazine of Oct. 24, 1829, No. 324, relative to the putting "rollers" in the place of the surfaces that the locomotive carriages now go on, I should like to offer you some particulars in furtherance of his scheme, but that would be useless, until it is ascertained by what contrivance those rollers are to be put in motion. "W. B." seems to have overlooked that the motion of the machine is dependent on the wheels of it, impelled by the power of the materials within it; and that deprived of its own wheels, and their moversteam-the machine must stand still. However, where horses are used, I think his scheme worthy a thought, and that all difficulties would be removed. I should be glad to see this noticed by Some competent practitioner of experience in your Magazine. I am, Sir, yours, &c.

C. H.

Sir, Although I take a lively interest in railways and railway carriages, and am by no means of the opinion of your correspondent "B," yet I do not see how the wheels in any of the carriages are propelled; and if you will be so good as explain how the wheels of "The Novelty" are put in motion, you will greatly A YOUNG READER. oblige,

[If our "Young Reader" will study a little more attentively the engraving on our 130th page, and imagine to himself what will be the effect on the bell-crank E, and connecting rod D, of alternately moving upwards and downwards the sling F, he can scarcely miss perceiving that that effect must be to turn the wheels continually round. This is commonly known by the name of the simple crank movement, and was first devised by Watt.-EDIT.]

Cycloidal Pendulum.-Sir, Some time back I invented a pendulum, which oscillates in a cycloid. I believe rewards have been offered for a pendulum of this description, because some great advantage would accrue to the astronomer, from the equable motion which mathematicians say must result from its describing a cycloid. Any gentleman informing me what the rewards are, by whom they are offered, and how they may be obtained, would confer a benefit where it is needed.

INDIGENS.

[We are not aware that any reward has been specifically offered for such a pendulum as our Correspondent states he has invented; but it being one of the peculiarities of the cycloidal curve, that a pendulum wheel, oscillating in it must perform all its vibrations in equal spaces of time, such a pendulum would supply so ob. vious a desideratum, in the measurement of time and determination of the longitude, that the inventor could scarcely fail to reap an ample reward by the disclosure of his invention.We take it for granted that our Correspondent is aware of the cycloidal pendulums invented by Huygens and De la Hire, and that his invention is something more perfect than either. EDIT.]

Perpetual Motion. Sir, I have read much in your Magazine about perpetual motion, and have studied this disheartening question many years before your work began. In No. 319, I see there is an account of a perpetual motion invented by one Richard Von Dyke, of America. I do not suppose any one can understand what that machine is from such an account; but no doubt it was the best you was able to procure. I verily believe that I invented the same thing a few months ago, but was prevented from putting it to the test of experiment by great troubles in my family. The doctors and the undertakers had taken away all my fiddling money; otherwise, I should have tried the thing before this time. If a few of your Correspondents will favour me with their addresses, I will appoint a time and place to have their united opinions on my scheme. But I hope no one will apply to be of the number who does not know something about pneumatics: 'I do wish that person to be one who wrote on the subject, p. 399, No. 312. I remain, Sir, your humble servant, R. W. FRANKLIN.

North-place, Wilsted-street, Somers'-town. P. S. When the gentlemen have examined my drawings, I wish some one of them to give your readers an account of it.

MISCELLANEOUS.

A Capital Filter for Four-pence!-Buy a common earthenware funnel, put a small piece of clean sponge at the top of the pipe inside, and over that a handful of fine gravel; then fill it up with water, and, after passing through, it will come out as clear as crystal. Thus you have quite as good a filterer for domestic purposes for four-pence, as can be purchased for as many pounds.

Musical Automata.—A mechanician, brother to the celebrated Maelzel, of Vienna, has constructed at Boston a set of musical automata, no less than forty-two in number, which compose a complete orchestra, and execute several of the most difficult pieces of music in the most perfect mauner, among others, the Overtures to Don Juan, Giovanni, Iphigenia, and La Vestale Those which excite the most admiration and wonder are the violin-players, which execute their portion of the music precisely as if they were living performers, viz. by the motion of the fingers, &c. A company of Americans have offered the artist 300,000 dollars for this extraordinary and unrivalled piece of mechanism; but the price demanded is 500,000 dollars, and it seems probable that it will be obtained.

King's College-The piles are now driving into the ground for the foundation of the King's College. From the proximity of the building to the bed of the river, and the nature of the soil, this is a work of great labour, and requires infinite care.-Sunday Times.

News for the Needle-Makers-An Englishman writing from France says, "The needle and pin manufactories around Aix-la-Chapelle are half a century behind England in the qualities of the articles, and a case of real English needles is a most acceptable present to a Belgian lady. -Morning Herald.

Discovery of Coal in Van Dieman's Land.A very fine vein of coal has been discovered in Van Dieman's Land, upon which a survey has been held, and some experiments tried, in order to determine its fitness for use on board of steamvessels, which, it appears, have been fully satisfactory.-Sunday Times.

Preservation of Apples.-It is the practice of some persons to pick apples in October, and spread them on the floor of an upper room. The practice is said to render apples more durable by drying them; but I can affirm this to be a mistake. Apples, after remaining as long on

the trees as safety from frost will permit, should be taken directly from the trees to close casks, and kept as dry and as cool as possible. If suffered to be on the floor for weeks, they will wither and lose their flavour, without acquiring any additional durability. The best mode of preserving apples for spring use I have found to be the putting them in dry sand, and as soon as picked. For this purpose I dry sand in the heat of the summer, and late in October put down the apples in layers, with a covering of sand upon each layer. The advantages of this mode of treatment are these: the sand keeps the apple from the air, which is essential to their preservation; the sand checks the evaporation of the apple, thus preserving their full flavour, at the same time any moisture yielded by the apple, and some there will be, is absorbed by the sand, so that the apples are kept dry, and all mustiness is prevented. My pippins in May and in June are as fresh as when first picked; even the ends of the stem look as if just separated from the twig.-Massachusett's Agricultu ral Rep.

Discovery of Pure Gold.-A beautiful speci men of virgin gold was lately found in a tinstream in Cornwall. It is about the length and thickness of a lady's little finger, though less regularly formed, and weighs about two ounces. Its intrinsic value is equal to nine guineas; but, as a specimen, it is invaluable.

In our next we shall give an engraving and description of the steam engine carriage of Sir Jaines Anderson and Co.

Erratum-In the statement given in our last No. (p. 165) of the cost of the fuel per mile expended by "The Novelty," for "oue farthing" read" one halfpenny." Mr. D. of Newcastleon-Tyne, who makes this error the ground of a serious charge against us, observes, that it is one which" any child who knows arithmetic" might easily detect. We agree that it is so-an error so palpable that no person, man or child, could be misled by it; but we think our Correspondent might have seen in this very circumstance reason enough to infer that it could not possibly have been intentional on our part. It was, in truth, an error of the press entirely; arising from the "one halfpenny" being expressed in the original MS in figures (3). and that rather indistinctly. We have elsewhere, in the same page, stated most explicitly that "The Novelty" worked with only two-thirds less fuel than any other engine." At a farthing per mile the rate would have been five sixths less.

Messrs. Cope and Sherwin's reply to Mr. Hopkinson in our next.

Communications received from F. F. O. B., A, Mr. Dowling, P. P., Peter, R. C. jun., Mr. Davy, T. F. R., and A Reader at Liverpool.

LONDON: Published for the Proprietor, by M. SALMON, at the Mechanics' Magazine Office, No. 115. Fleet Street; where Communications for the Editor (post paid) нie re. quested to be addressed.

M. SALMON, Printer, Fleet-street.