408

The 5 per cent. method is founded on the same principles as the foregoing, and is, in my humble opinion, the shortest and most correct that can be devised, viz.-Suppose the interest of 2191. for 25 days was required: 219 × 25 1-3d

1-30th

1-300dth

H

5475

1825

1825

1-10,000dth=

1825

7500 75

75

369,863, &c.

27,000,000

1

3

x +

300

-, &c. 100 shillings

=

27,000,000.
369,863,&c.

I remain, Sir,
Your constant reader,

G. U. A. P.S. I never give myself the trouble to multiply by 20, 12, and 4, to reduce the decimals of a pound to shillings, pence, and farthings; but, by inspection, I double the figure next the point for shillings; if the next figure be 5, or upwards, take 5 from it, and add one to the shillings; there the second and third figures are farthings, after deducting I for every 25 in them.

BURMESE IMPERIAL STATE
CARRIAGE.

The Burmese Imperial State Carriage, which has been captured in the present sanguinary Indian war, has reached this country, and is now preparing for public exhibition. It is said to be, without exception, one of the most singular and splendid works of art that can possibly be

conceived, presenting one entire blaze of gold, silver, and precious stones; of the latter the nuniber must amount to many thousands, comprehending diamonds, rubies, sapphires (white and blue), emeralds, amethysts, garnets, topaz, cats eyes, crystals, &c. The carving is of a very superior description, the form and construction of the vehicle extraordinary, and the general taste displayed throughout the whole design is at once so grand and imposing, yet at the same time so chaste and refined, that we are told it may defy all rivalry even from European workmanship. The warlike power and resources of this surprising people are at present exciting universal astonishment and attention: this new object attests the fact that, in taste for design, and skill in execution of works of art, their talents have been equally hidden and unknown to us. The carriage stands between twenty and thirty feet in height, and is drawn by elephants.

GRAND BALLOON.

Selim Ogal, of Smyrna, has just finished one of the largest Air Balloons that has ever yet been made : it is 140 feet in diameter, and the parachute 22 feet in circumference, and he intends shortly to make an ascension.

Selim will be the first Turk who ever approached so near the regions of their prophet in so 24 Tille frail a vessel.

VEGETABLE TALLOW.

A Vegetable Tallow, extracted by boiling from the fruit of the Vateria Indica tree, growing in Canara province and others on the western coast of the peninsula of India, which sells in Mangalore at about 24d. per lb., has lately been brought to London, in a very hard and tough cake, experimented upon by Dr. B. Babington. It is easily made into mould candles, which afford as bright a light as the best animal tallow, and without any unpleasant smell, even when blown out,

3

SIR,-In page 64, vol. 111. of your Magazine, a Subscriber wishes to have a description of an invention for regulating the Heat of Hothouses; I shall be happy to give him all the information in my power.

AA are a glass tube, from two to three feet in length, hermetically sealed at one end, and united at the other to a capillary tube, BB, with an intervening and also a terminating ball, C and D. The largest tube, and half the intervening ball, are filled with spirits of wine; and the smaller, and half of both the balls, with mercury. The tube is fixed by its centre in a brass frame, E, and nicely balanced. It is evident, then, that every change in the temperature of the atmosphere will produce a change in the position of the centre of gravity of the tubes. One degree of heat, by expanding the spirit, will press on the mercury at C, and drive part of it over to D, which end will, in consequence, descend like the beam of a pair of scales.

In order to apply it to opening

windows, valves of chimneys, or flues and steam-cocks, Mr. Kewley, the inventor, uses a metal cylinder, F, from 7 to 14 inches in diameter,and from 18 inches to 2 feet in length, with an accurately fitted piston, G. This cylinder is placed in any 'convenient situation, and a barrel filled with water is placed on an elevated situation, with a pipe from it, H, to a point directly under the thermometer, and not higher than the bottom of the cylinder; here it joins the pipes I and K; I, a waste pipe, and K, a pipe entering the cylinder below the piston. At the point, L, is a tripartite cock, the handle of which, M, turns only to the extent of one-fifth of a circle; when turned to the right, it opens a communication between H and K, when the pressure of the water raises the piston, and opens the sashes, &c. by the chain, N; when the cock is turned to the left, this communication is stopped, and one opened between I and K, by which the water escaping the piston descends, and the sashes,

410

&c. are shut. The cock is worked by the wire, PP, fig. 1st and 2nd, joined to the thermometer frame at one end, and to the handle of the cock at the other. It is set to any required degree of heat by the sliding scale, which changes the centre of gravity of the tubes.

A perfect specimen has been exhibited at W. and D. Bailey's, 272, Holborn, since 1818; and the details of construction will be found in the Patent Office, 1816, or the Repertory of Arts for January, 1821. I am, Sir,

Your obedient servant,

66

J. L. E.

THE AIR AND WATER ENGINE." SIR,-In looking over your 104th Number of the Mechanics' Magazine, I observe a drawing and description of a machine, which your Correspondent (a Member of the Bolton Mechanics' Institute) calls a Water and Air Engine, from which (per his supposition) he can have power, almost ad infinitum, at a very small expense compared with the steam-engine; but I am much afraid that his supposition will be found altogether fallacious. Nevertheless, as he has asked the opinion of others of your Correspondents, I will venture to give him mine. I shall, at present, pass over the first part of his communication (where he says he shall make an air and water engine into eight horses' power by the assistance of a four-horse steam-engine, &c. &c.) and come direct to his question, which is put in so very tangible a shape as makes it quite easy to handle it. It is in substance this:-What number of horses' power will be required to pump water 42 feet high, sufficient to supply two cylinders, each 24 inches in diameter, and making 22 strokes of five feet each per minute? Now, according to this, a column of water 220 feet long and 24 inches diameter must be supplied every minute, and lifted to the height of 42 feet, for the use of his water and air engines. This is no joking matter, I can assure him ; as he wishes to know what power will be required to do it, I will endeavour to inform him.

and

At what power he will estimate his machine, when completed, I do not know; but here we see that it will require no less a power than fifty-four horses to lift water necessary to work this air and water engine.

The next thing will be, to try if we can find the power of this machine after water is supplied to it, and in doing this we will allow him the full weight of the atmosphere (15lbs. to the square inch), and say nothing about the friction of his machine. First, then, the area of the cylinder =452,39 × 15 × 220 = 1492887lbs. lifted one foot high in one minute, and 1492887 45,23 horses' power; from

=

33000 this it is evident that, instead of gaining power, he will be minus nearly ten horses! The reason of this is obvious, because he pumps his water 42 feet high into the cistern, L (which, by-the-bye, I cannot find in the drawing), and he has only the advantage of 34 feet fall, or, in other words, the pressure of the atmosphere to gain power by. Even if this were not the case, and the water were only raised to the same height as it had to fall, the rising and falling columns would only then balance each other, and he would be minus the friction of the two engines, without still gaining one pound of power.

But

I would here beg leave to remind your Correspondent, that water cannot be made use of, as a power, to advantage in any other way than by its gravity, and the best application of this is upon the water-wheel. should he (contrary to my expectation) succeed in convincing himself and me, that one single pound of power will ever be gained by the air and water engine more than is required to supply it with water, I then will engage, with great pleasure, to send you a complete plan of valves and working gear, with a mode of governing the said engine.

As I have no other end in view but of giving and receiving instruction, I hope your Correspondent will not find fault with my feeble attempt to undeceive him.

I am, Sir, Yours respectfully,

A MAN IN THE MOORS.

August 30th, 1925.

HOW TO RESTORE THE COLOUR or

WOOLLEN CLOTHS DISCHARGED
BY AN ACID.

SIR,-Having accidentally spilled some strong solution of oxalic acid on a pair of black trowsers, the colour was discharged, and the place, which was large, turned of a yellow colour. The following day I dissolved some pearlash in water, with the addition of an equal portion of quick lime, and sponged the part with it. The alkali rendered the stain and the adjacent part, which was wetted, of a dark foxy brown; a little vinegar, now applied, restored all to its pristine black, and I defy the most experienced scrutinizing Hebrew to discover the place.

I remain, Sir,
Your obedient servant,
ALKALI.

A House-Spider was placed by Mr. Bell on a small platform, in the middle of arummer full of water, the platform being about half an inch above the surface. It presently made its escape, as was anticipated, by suffering a thread to be wafted to the edge of the glass. Mr. Bell, suspecting it might have been assisted by the water being so nearly on the same level, poured some of the water away, and placed the spider as before. It descended by the stick that supported the platform, till it reached the water, but finding no way to escape, it returned to the platform, and for some time employed itself in preparing a web, with which it loosely enveloped the abdomen, by means of the hinder legs. It now descended, without hesitation, to the bottom of the water, when Mr. B. observed the whole of the abdomen to be covered with a web containing a bubble of air, probably intended for respiration, as it evidently included the spiracles. The spider, enveloped in this little diving-bell, endeavoured on every side to make its escape, but in vain, on account of the slipperiness of the glass; and

.

411

NEW SCARLET COLOUR.

Mr. Badams has recently described a process for obtaining scarlet chromate of lead, and highly recommends its use as a colour either in painting or calico printing. He prepares the scarlet chromate by boiling yellow chromate of lead with potash, and has made several experiments upon the properties of the scarlet colour thus obtained. It appears that it may be made what is termed a fast colour in calico printing, and that it is a durable and beautiful colour when used with oil, possessing considerable body. It is not degraded in its hue by admixture with white lead, as vermillion is; and it also mixes with other colours. As a watercolour it has not been sufficiently tried to render it certain that it will not blacken; but several slips of card and thin paper, painted with it, and hung up in situations likely to affect colour, have not, in some months, perceptibly diminished in brightness. Mr. Badams very justly remarks that, should it succeed, no tint would be a more desirable accession to the pallet than a bright and permanent scarlet, or scarlet orange.

412

SIR,-It has for some time been an object with me to obtain some authentic account of the number of Mechanics' Institutions, and Mechanics' Book Clubs, now existing in different parts of the country; and it has just occurred to me, that your very useful Magazine might be made the means of obtaining this most desirable information, by introducing a notice, inviting the Secretaries, or other Officers of such Institutions, to forward to the Editor the names of the societies to which they belong. To communicate, however, to such a return all the advantages of which it is susceptible, it would be most desirable to include in it the number of members belonging to each society, the average number of readers which attend the libraries or reading rooms, the number of volumes of which each library consists, and the rate of the weekly or annual contributions, brought up to some definite period, say Michaelmas, 1825. Such returns, when collected by the Editor, might be tabulated and reduced into a systematic form, and printed in the Mechanics' Magazine; thus affording the materials of much important information, not only to the present generation, but to the historian, whose duty it may be, in after ages, to trace the causes that have operated in accelerating the march of useful information among the working classes. And if annual returns of the same kind could be made, and tabulated according to the best form, the successive steps which mark the growth and extension of mechanical information might be traced from year to year, and from one generation to another,

To your most useful Magazine, dedicated so exclusively in its objects to the diffusion of sound mechanical information among the operatives-the most numerous class by far of our active and enterprising community-the future investigator of the causes of our unrivalled superiority in arts and manufactures will naturally turn, for the materials to assist him in his magnificent survey. Few surveys, indeed, could present more striking and impressive results. It would interest both the philanthropist and the philosopher; it would form a sort of skeleton map of the state of useful knowledge every year would tend to beautify among the operative classes, which and fill up.

For want of authentic information of this kind, if we attempt at any time to trace the causes that have led to

results so interesting to human happiness, as are daily presented to our contemplation, we soon become enveloped in uncertainty and error. Let us, however, hope, by the attention that has been latterly awakened to statistical inquiries in this country, that our successors may not have occasion to say of us, what we sometimes have good occasion to say of our predecessors. Let us remember, "that it will equally reflect on the present generation, when they, like the foriner, shall become the past, unless some means are adopted

to furnish our successors with those

interesting facts, the want of which leaves us often enveloped in the shades of uncertainty and error.*" I remain, Sir, Your obedient servant,

GEORGE HARVEY, F.R.S. Plymouth, Sept. 21st, 1825.

P.S. The reader is requested to mark with inverted commas the 11th, 12th, 13th, and 14th lines, from the bottom of the second column of the Letter in page 315; and also the 19th, 20th, and 21st, and the five concluding lines of the second column of page 316.

*Wimpey on Economical Registers, vol, 1. Manchester Memoirs.