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nr-1 a?
(np-1) (np—2) as

&c. Or, if the terms be mul. 2


n'a na? na3 3 no a3 2 na3 tiplied out, = l + na +

+ &c.; 2:3

23:P 2.3p? which is a series consisting partly of

whole of the latter may be brought as terms not containing x, and partly of nearly as we please to 0; so that by those which have powers of * only in omitting these, we have, for the limit of the denominators. "Now, it is obvious, the expression, that by making x sufficiently large, the

na a?

nda A = l + na +

n' a'

+ &c. 2

2.3 2.3.4 But this series is known to be the one On the continuous hypothesis = 100 x for { * *, (€ being = 2.718, &c., the base

100 of the Napierian system of logarithms.) anti-log.

=2711. 16s. Od. nearly.

230.258 whence A = {ne, or in other words, the amount produced in n years by

The amount of £1000 at 5 per cent. £ P put out to compound interest at r per

per annum, for 20 years, would be,

1000 cent. per annum, upon the continuous

On the common supposition hypothesis, will be = P x number to

(1:05)20 = 26531. 6s. Od.

On the continuous hypothesis = 1000 x Napierian log. P x natural

100 100


27181, nearly.

230.258 number to common log.

The same for 100 years. 230-2589

On the common method = 1000 (1:05) 100

about 131,5001. An example or two will show the dif

On the continuous hypothesis = 1000 x ference between the results of this and

500 the common supposition.


about 148,4001. The amount produced by £100 at 100

230.258 per cent. per annum, in 1 year, would I am, Sir, yours obediently, be, on the common supposition 100

W. Pole. (1 + 1)' = £200.

Bloomsbury, February 3, 1842.

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NEW MATERIAL DISCOVERED. Sir,- It is well known that the Ame the year, and delivered in the potteries ricans are endeavouring to supply them. at a less price than flint or clay. It is selves with earthenware, and that they free from any metallic mixture, and does are in possession of the materials, which not contain (excepting an almost imperat some future day may be made a ceptible portion of carbonate of lime,) greater use of. In order to retain the anything but pure silica and alumina, of superiority in making pottery, porcelain, which there are about four-fifths of the &c., that Staffordshire has hitherto had, former, and one-fifth of the latter. It we must not only consider the best mode would not require the expensive and of combining our earths and minerals, but tedious process of burning and stamping also the cheapest plan of obtaining them. like fint, but merely grinding from a Under this impression I have succeeded state of siliceous sand to powder; and in obtaining a material which is likely to containing already one-fifth of alumina, be extensively used in the fabrication of would only require an addition to be fit glass, pottery, Porcelain, &c. It possesses for the potter's use. It is difficult to meet one great advantage over articles of si with such a pure alumina-siliceous commilar properties now in extensive use, pound in nature. The silica has been that of being cheaper. It may be ob extracted easily by water from the native tained in any quantity, at any season of earth and used at BIRMINGHAM and St.

He has been bred i' the wars since he

Helen's in the manufacture of Flint and plete protection against the spreading of
PLATE GLASS, and was found equal, if fire, in all the possible casualties of ordi-
not superior, to the sand from the Isle of nary conflagrations.
Wight, now in such general use.

Witnessed, as these experiments have Any manufacturer wishing to make a been, by the highest and most competent trial of this new production, may have a authorities, it is perfectly futile for Cosample on application to the writer, lonel Macerone, at this time, to misre

SAMUEL SALT. present the facts, or to underrate the Liverpool, 32, Mulberry-street, Feb. 9, 1842. value of the protective powers of the


In order to show his intimate know

ledge of the ingredients of which the firePATENT FIRE-PREVENTIVE PLASTER, VIN

preventive plaster was composed, Colonel DICATED FROM THE ASPERSIONS OP

Macerone says, “I took a portion of it COLONEL MACERONE.

home, and found it to consist of Roman could draw a sword, and is ill schooled in boulted

cement, size, and alum." The mode of language; meal and bran together he throws with

chemical analysis by which the Colonel out distinction."

can resolve one composition into another Sir,-I had hoped that my last com must be a very singular process. Une munication on this subject would have fortunately, however, either for Colonel sufficed to show Colonel Macerone, that Macerone's honesty, or for his chemical he was greatly mistaken with reference skill, no such matters as Roman cement to the properties of the Fire-preventive or alum enter into the composition of the Cement; and that he had better either article in question ; and I am the more obtain more correct information, or be surprised at the temerity of Colonel Masilent upon this subject.

cerone, in venturing to put forth such By your last Number, however, (page mistatements upon this subject, be116,) í perceive that my friendly caution cause the actual components of this has been thrown away

plaster are no secret. The specification " He winna tak the hint."

of the patent, duly enrolled, gives the On the contrary, he continues to write public free access to all the information most disparagingly of the “anti-phlo- they can desire upon this head. The gistic plaster," alias, “the bubble ce basis of the fire-preventive cement or ment:" with what justice, your readers plaster is, slate and calcined river sand. shall be enabled to determine.

The refuse pieces of slate are ground to The highly satisfactory experiment in a fine powder, and with the sand are Dorset-street, Clapham-road, on the 6th boiled with a small quantity of tar, rosin, of June, 1838, and the (if possible) still and the strongest glue, or other animal more conclusive demonstration of the ef. gelatinous substance. When brought to ficacy of this composition, in Trafford. the required consistence, the mixture is street, Manchester, on the 23rd of Octo dried, powdered, and packed in casks for ber following, have been duly recorded sale. When required for use, it is temin your Gazette. Similar public exhi. pered with water, as in mixing common bitions have been made in New York and mortar. St. Petersburgh. Many private experi.

Colonel Macerone further states, that ments have also been witnessed by archi

at the house in Dorsei-street, he saw tects, builders, &c., and by the officers in “the tubs of Roman cement, those of connexion with Her Majesty's Board of size, and others, which, not being opened, Ordnance and Dock-yards, Colonel Fan

I cannot swear that they contained the shawe, Captain Jebb, Mr. Ewart, Mr. alum.” No such materials as Roman Lloyd, Mr. Sylvester, and others, who cement, size, or alum, were on the prenot only expressed their confidence in its mises ;* the “preventive cement' was properties, but have given orders for its delivered in tubs ready for use, requiring use in the Lucifer steam ship, and the nothing but the addition of a proper Model Prison erected under the superin- quantity of water. Indeed it is necessary tendence of the Commissioners of Woods to mention, by way of caution to parand Forests; the experiments having sa. tisfactorily demonstrated that the • Pa. Surely if such ingredients composed the plaster,

they would have been combined in the manufacture, tent Fire-preventive Plaster" is a com not in the using!


135 ties using the preventive plaster, that will be necessary to have a chain or rope Roman cement, if mixed with it, spoils hung in each chimney. The only objecit. Sach a mixture greatly impairs its tion I can see to this plan is, that in the antiphlogistic powers, and never hardens course of time the chain or rope will be properly; I have seen specimens which apt, in rubbing against any acute angles, remained soft and friable, while the to work into the joints of the bricks, as cement alone attained a stone-like hard chimneys are now constructed. To obness.

viate this, I propose to insert in the The determined hostility with which chimney, where any very acute angle Colonel Macerone has all at once attacked occurs, a metal brick, with one of its the fire-preventive plaster-professing as corners well rounded, which would form he does, to be a fellow labourer in the an easy surface for the chain or rope to cause of “ fire prevention"-is most sur

pass over. prising. Nor will I pretend to explain To all straight chimneys, the jointed ihe wherefore. Neither can the materials, rods, (Glass's machine,) are well adapted, of which the fire-preventive cement is and as one set will answer for many coma posed, be of any very great conse chimneys, they will on that account be quence, so long as it retains the remark found the most economical. If the above able fire-resisting properties, which every plan were generally adopted, it would only trial has hitherto proved it to possess. be necessary for adult sweeps to go about

Without pursuing the subject further, in the morning with brushes of two or I beg to remain,

three sizes to attach to the chain or rope, Sir, yours respectfully.

and a bag to carry away the soot. WM, BADDELEY. Should you think the above worthy of February 14, 1842.

insertion in your valuable Magazine, you will further oblige, Sir,

Your most obedient servant, MECHANICAL CHIMNEY SWEEPING.

A. M'GILLIVRAY. Sir,--On reference to page 337, vol.

38, Clarendon-square,

Feb. 1, 1842. ii., of your instructive Magazine, you will find fully described by G. W. T., with drawings, the first and best of the plans MECHANICAL CHIMNEY-SWEEPING MR. suggested by your correspondent, Mr. EMSLIE IN REPLY TO MR. BADDELEY. Emslie, in a recent Number. An im.


Feb. 9, 1842. provement upon this plan I first made public in 1837, the object of which was

Sir,- I feel assured you will do me the to obviate the necessity of going on to the

justice to give early insertion to a few words top of the house every time a chimney

in reply to the strictures of Mr. Baddeley,

on my plans for mechanical chimney-sweeprequired cleaning. A model of my improvement is exhibited in the Polytechnic ing, published in your 964th


I am, indeed, much obliged to Mr. BadInstitution, Regent-street, and may be

deley for giving me credit for motives of hudescribed as follows :- Across the top of

manity in submitting these plans to the the chimney or chimney-pot, rather to public; but, after showing himself so streone side, is placed a round bar of iron, nuously adverse to the employment of little over which runs a small endless chain, children in the sweeping of chimneys, I think (jack-chain,) or incombustible rope, des he might have left his mind open for the uncending to the fire-place, where it passes prejudiced consideration of every variety of under another round bar, placed in any suggestion for the introduction of mechanical convenient corner at the bottom of the means, instead of so strenuously advocating chimney, to prevent the chain from

one invention, to the exclusion of all others. twisting. A whalebone brush, or wisp

Could I have persuaded myself that Mr.

Glass's machine was a perfect instrument for of heath, &c., is to be attached to any part of the chain or rope, and by moving

the purposes in question, I should not have

troubled myself to devise new means. I upit up and down, it will effectually bring

hold, however, and shall demonstrate thisdown all the soot, however crooked the

that the rope, weighted brush, pulley, and chimney may be. This accomplished,

flue-door mode is much superior to Mr. detach the brush, clear away the soot out Glass's, in many instances. It is all very of the grate, and place the lower end of well for Mr. Baddeley to say, “ There is no the chain at the side of the chimney. It chimney in existence, capable of being swept

by the weighted brush, that could not be the apertures A and C would be required. It swept far better, and with less injury, by is also apparent that the lodgement of soot Glass's machines.” But where is the proof which would take place at those parts of of this? Mr. Baddeley cannot expect that fiues similar to that lettered E could not be the public will take his mere assertion of the removed by Glass's brush. A very great thing as an absolute fact. I may with more advantage likewise attending the pulley and reason, I think, ask-Can a single flue be rope is, that they can be made of very great pointed out, which Glass's machine is capable use in the formation of a scaffold in the inof cleansing, that the weighted brush mode terior of the chimney, for the performing of is not equally able to effect? I am sure that any repairs therein. all those who understand the respective pro Wishing every success to the “good perties of both methods, and are disinterested cause,” as to the success of either, will answer in the

I am, Sir, negative. Suppose the question reversed,

Obediently yours, what do we arrive at ? Why, at this; that

JAMES A. EMSLIE. by numerous soot-doors the most perversely constructed chimney may, by Glass's machine, be swept ; but that by many fewer

IMPROVED CANDLE HOLDER. contrivances, and much more easily, the same construction of chimney may be effectually cleaned by the weighted brush. The following sketch will illustrate the difference:


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Fig. 1.

Fig. 2.
Sir,-Should the above design for a
candle holder be deemed worthy of a place
in your valuable Magazine, it may be
the means of preventing many a spot of
grease from candles being awry in their

A, the candlestick.
B B, the candle holder.

CC, two springs on each side of the socket to keep the holder against the candle.

E E, two pins holding the candle holder in its position, and sufficiently loose to allow it to play.

D, the candle.

Press with both fingers on the two
lower ends of B B, protruding, as at
fig. 1, which will open the holder to ad-
mit the candle being placed, as seen at
fig. 2.
I remain, Sir,
Your obedient Servant,

J. B. B.
Guernsey, November 22, 1841.

A B C D are soot-doors, which I think Mr. Baddeley will allow would be required for sweeping a chimney of the intricate construction here represented, (I give it such a form for the sake of clearer illustration, though I should hope few such exist,) by means of the machine he so strongly advocates; whereas by using along with my suggested flue-doors and pulleys a long handled scraper, (evidently a more useful article for cleansing horizontal flues than a brush,) only

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Sir,-In No. 966, Mr. Baddeley has given an account of the bursting of a pipe under peculiar circumstances, which he designates a “ Singular Phenomenon.” I was surprised that Mr. Baddeley, with his stock of general knowledge, should find the solution difficult.

My explanation is this :—That part of the pipe situated outside the house being

colder than the portion which is inside, B

acted as a condenser to the vapour rising from the surface of the water in the shorter leg of the syphon. The vapour, as it became condensed upon the sides of the colder parts of the pipe, would

descend to the stop-cock at the lower C end, and would accumulate there. The

frost would perform the remainder of the operation.

By the rising and falling of the water in the cistern, and consequently, in the shorter leg of the syphon, the inclosed

air would be alternately compressed and D

dilated, which would increase the evaporation, as the variable density of the air would give it different capacities for retaining the aqueous vapour; and, by the falling of the water in the shorter leg, the sides of the pipe would be left wet, and

thus the evaporating surface would be Sir,- A few days ago as I was viewing much inc

much increased, forming a complete the operation of a newly-erected steam distilling apparatus upon a small scale. engine, I thought proper to open the It may be asked, why the pipe should cock in order to empty the grease cup

burst at a distance of 9 inches above the into the cylinder. But instead of doing cock? The answer would be, that the this during the ascent of the piston, that water is supposed to have stood at that is, when the space above the piston was height, and the upper surface becoming void, I unthinkingly did it during the frozen first, would strain the pipe in that descent; the consequence was, that the part, and the condensation still going on, steam blew out the contents of the grease would cause the ice to accumulate there cup with very considerable force, and and complete the fracture. scattered them all over me.

To save

If this view of the case should be others from being exposed to such ac deemed satisfactory, perhaps it may assist cidents, I beg to suggest that the cup in the explanation of the bursting of gas should be formed in the manner repre pipes, for they are subject to accumulasented in the prefixed sketch. It will be tions of a fluid, more or less watery, in advisable, previous to allowing the oil the lower situations, and are liable at or tallow to enter the cistern C, to ex times to be frozen. tract the air therefrom, by closing the

Yours respectfully, cock D, when a vacuum will be pro

T. CLAXTON. duced immediately beneath: also to make

29, Harrington-street North, Hampstead-road, the cistern C a little larger than A, in

February 14, 1842. order to preserve a small portion of air

[Somewhat similar explanations have above the tallow, after the cock B is

been furnished by S. E. A., and An Old closed, the expansion of which would,

Subscriber.--En. M. M.] on opening the cock D, cause the oil or tallow to leave the cistern more freely. I am, respectfully, yours, &c.


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