Sidebilder
PDF
ePub

138

ON CEMENTING WATER AND STEAM-PIPE JOINTS.

labour to the animal, and much unnecessary strain upon the woodwork.

While upon this subject, I am anxious to know the opinion of some of your Correspondents upon double or under-springed carriages. They seem to me well calculated to preserve the carriage part, but I think, besides the extra weight, that they add to the difficulty of draught; inasmuch as any person sitting in the inside of the chariot will perceive, upon passing any obstacle, that he is subjected to a second rocking or undulation before the first has ceased, and that the horses have increased labour till they receive their steady pull. This inconvenience might, perhaps, be diminished by having the under-springs longer, so that they, as well as the whipsprings, might get into action, and again become quiescent at the same time.

I am, Sir,

Your most obedient servant,

D. P. BUNGY.

REPLY OF MR. WAY, ON CEMENTING WATER AND STEAM-PIPE JOINTS.

SIR,-Your nameless Correspondent, who writes from Bow (p. 389, vol. III.), calls himself a "Practical Engineer;' but without better authority than his letter, I should doubt his claim to the title he assumes. When I had stated so distinctly, that the water was pumped into a reservoir, about 900 feet from the greatest extent to which the water was brought that pipes of three inches in diameter were used; that part were flanged, and part spiggot and faucet; and that the water was raised in my house from the pipes, through lead ones, a height of about eight feet; if he had been what he pretends to be, he would have required no other information to enable him to calculate the pressure of water upon the joints; which, for me, who am not a practical engineer, might possibly have proved a more difficult task. He must also, I think, have been aware that, as the easiest way to fill the reservoir, the water would be pumped into it at the top, on the side nearest the well; and that, for the sake of economy, it would be conveyed into the pipes, by fixing them at the bottom of the reservoir, nearest the honse, and, of course, not connected with the pump; and that the

pipes would, when laid down, remain fixed and immoveable. There were various forks in some of the pipes, on the right and left sides, in case a supply of water should afterwards have been wanted in those directions; those were plugged, and never used; the water was taken from the pipes at three different left in the upper surfaces of the pipes. places, about 100 feet apart, by orifices What jar or shake the pipes could feel from the velocity of the water passing through them, am quite at a loss to find out, as the pipes would always remain full, except when water was drawing from them; and as that was from lead pipes, and cocks of about an inch in diameter, it would be scarcely felt on pipes of three inches bore. Your Bow Engineer states, that he uses iron borings pounded, which must be difficult to be got in most places (I fear he means to bore your Henley inquirer). To be sure, iron filings can be got in most country smiths' shops; but then these cannot need pounding. The place where my pipes were laid down was very near to the yard of a shipwright, who did a good deal of work, and for more than thirty years I was very frequently in the yard, viewing vessels building aud caulking, and I have some little idea how the latter work is done, but I can form no conception how such a substance, as your Bow Engineer describes, can be caulked into the ends of the joints of iron pipes. I am certain it cannot be by what the caulkers call their art and mystery, namely, drive and go; if it is, cast iron pipes would soon go to atoms. I cannot here lay my hand on the directions given me by the agent of the Neath Abbey ironfoundry for a luting, where that is requisite, and at this distance of time 1 cannot remember all the materials of which it was composed: borax was one of the principal articles, but I am certain there were no iron borings in it, as recommended by your Correspondent. Between us, however, I dare say we shall afford sufficient information for the purpose of your Henley Correspondent. In my letter, I certainly had no idea of giving information to real practical engineers, being well aware that they were too well informed for any thing I could write to be of the slightest use to them; I considered (as I stated nothing but plain facts, and those in the plainest way) that if they found a place in your very valuable publication, they might afford some useful hints to persons in the same situation in which I was placed, as well as to such sort of mechanics as i then employed.

The friend who supplied me with the Roman cement I used, has been dead some years; but I have before me a letter from his only surviving son, dated the 7th of March, referring me to your

CALCULATION OF INTEREST AT FIVE PER CENT.

Magazine for a description of an engine he meant to examine," which (he adds) I see, by a letter in a Number of last month, you occasionally look into. Thomas Everett came into the countinghouse one day, and I gave it him to read. He is highly pleased to find his name in print. I have employed him for several years, and I do not think there is a more honest man in existence, nor one that has your interest more at heart while working for you." This gentleman was born, and has always lived, in the parish in which my pipes are laid down.

I am, Sir, yours, &c.

A CONSTANT READER AND SUBSCRIBER.

139

But the first thing which strikes the scientific observer's eye is, the first antecedent is equal to the first consequent, and therefore may be both exterminated without altering the proportionality of the analogy as to

number

days.
365

1.

days.

25 :: 219

To meet my view of the true principles of proportion, we must make an alteration in the relative positions of the above remaining terms, viz.—

days.
365

[ocr errors]
[ocr errors]

days.
219 ::

25

[merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]

36500) 27375 (0

Here we find the product of the antecedents greater than that of the consequents, and we must proceed to bring the latter into the next lower denomination, which, being shillings, we multiply by 20.

27,375
20

365,00) 547,500 (15s. true ans. 1825

It is here very evident that the quotient 15, found as above, must be 157. sterling, therefore cannot be the true interest sought; but as some sensible gentleman may have discovered that the true answer was 15 shillings, he very shrewdly suggested, as a short cut, 15; therefore call the quotient shillings, and you will be right.

15 =

This being a mechanical mode of obtaining scientific results, induced me to think it may be particularly applicable to your widely-circulating and useful publication; allow me, therefore, to endeavour to explain all this to you. Let x equal the interest of one hundred pounds for one day; if the one hundred pounds be forborne for ten days, the interest will be ten times x. If ten hundred pounds be forborne for one day, and that the interest of one hundred pounds for one day equals x, ten times x must be the interest, the same as in the case of one hundred pounds for ten days, and we at once obtain the following corollary :-If any number of pounds be multiplied by be a sum, the interest of which for any number of days, the product will one day will be equal to the interest of the given sum for the given days. Now, on referring to our last analogy, we may read it thus:-As the whole year is to the number of days forborne, so is the principal sum to the fourth 219 proportional, which shall be the sum,

[merged small][merged small][ocr errors][merged small][merged small][merged small]

140 VARNISH USED FOR INDIAN SHIELDS-DOUGHTY'S RUBY PEN.

the interest of which for the whole year shall be equal to the interest of the given sum for the given portion of the year; aud we may demonstrate this from the well-known property of an analogy, viz. the product of the extremes is equal to the product of the

[blocks in formation]

That is, the interest of fifteen pounds for 365 days is equal to the interest of twenty-five pounds for 219 days. We have been searching for a thing required, and we have found a thing equal to it, which will answer our purpose as well as the original.

We were asked, what is the interest of twenty-five pounds for 219 days? and we have discovered that the interest of fifteen pounds for one year is equal to it; but the rate per cent. given is five: and it is evident that the rate five is the twentieth part of the principal sum, one hundred; therefore the interest of any sum for one year must be the twentienth part of itself; hence, the interest of fifteen pounds for one year, being equal to the interest of the given sum for the given days, we obtain the result by taking the twentieth part of fifteen pounds, viz. fifteen shillings.

[ocr errors][merged small][merged small][ocr errors][ocr errors][ocr errors][ocr errors][merged small][merged small]

buckler. The varnish is composed of the expressed juice of the marking-nut, semecarpus anacardium, and that of another kindred fruit, holigarna longifolia.

The shell of the semecarpus anacardium contains between its integuments numerous cells, filled with a black, acrid, resinous juice, which likewise is found, though less abundantly, in the wood of the tree. It is commonly employed as an indelible ink, to mark all sorts of cotton cloth. The colour is fixed with quicklime. The cortical part of the fruit of the holigarna longifolia likewise contains between its lamina numerous cells filled with a black, thick, acrid fluid. The natives of Malabar extract by incision, with which they varnish targets.

To prepare the varnish according to the method practised in Silhet, the nuts of the semecarpus anacardium, and the berries of the holigarna longifolia, having been steeped for a month in clear water, are cut transversely, and pressed in a mill. The expressed juice of each is kept for several months, taking off the scum from time to time. Afterwards the liquor is decanted, and two parts of the one are added to one of the other, to be used as varnish. Other proportions of ingredients are sometimes employed; but in all the resinous juice of the semecarpus predominates. The varnish is laid on like paint, and, when dry, is polished by rubbing it with an agate or smooth pebble. This varnish also prevents destruction of wood, &c. by the white unt,

VARNISH USED FOR INDIAN

SHIELDS.

Shields made at Silhet, in Bengal, are noted throughout India for the lustre and durability of the black varnish with which they are covered. Silhet shields constitute, therefore, no inconsiderable article of traffic, being in request among natives who carry arms, and retain the ancient predilection for the scimitar and

DOUGHTY'S RUBY PEN.

SIR,-In answer to the inquiry of your Correspondent, G. H., page 98, vol. iv. of your valuable miscellany, requesting the address of Mr. Doughty, the inventor and manufacturer of the Ruby Pen, I beg to inform him that it is No. 10, Great Ormond-street, London. By giving this publicity you will oblige,

Yours respectfully,

R. LEWTHWAITE. Rotherhithe, May 26, 1825.

[merged small][merged small][graphic][merged small][merged small]
[merged small][ocr errors][merged small]

At the Annual Distribution, this week, of the Rewards given by the Society for the Encouragement of Arts, Manufactures, and Commerce, there were fifteen awarded in the branch of mechanics. The following were the most remarkable :-

Mr. W. HARDY, Wood-street, Spafields, obtained the gold medal, for an instrument to ascertain very small intervals of time. The Secretary stated, that this instrument was so excellently constructed, that it would divide a second of time into 300 equal parts. It was used in the first instance at Woolwich, by the artillery officers, in throwing shells and other projectiles, and it had since been introduced at the Royal Observatory at Greenwich. Its functions were performed by pressing a spring, and, of course, the muscular power of different persons

would create in the instrument different degrees of motion, so that it was difficult to make an exact estimate of its truth. But all who examined it admitted that it was a very extraordinary piece of mechanism.

COLIN SHAKESPEAR, Postmaster-General, Calcutta, obtained the gold Vulcan medal, for a portable rope bridge.

This species of bridge, the Secretary observed, might be supported on that species of soil which was found in all the water-courses of India. The whole of the materials might be removed on the backs of bullocks from one place to another, and speedily fastened together with metal hooks and eyes. It was constructed on the principle of the chain bridge, and was extremely well adapted to military purposes in India and other tropical countries, where the water-courses are, in the course of a few hours, swollen to torrents. Three bridges on this plan had been constructed in India. The first was constructed near Calcutta ; after it had been removed there for some time,

142

EGYPTIAN ORE-WOODEN CHURCH CLOCKS.

it was taken down, and carried to the distance of eighty miles on the backs of bullocks. It was then re-constructed, and braved, without deterioration, the storms of the spring.

A more precise account of these bridges, called, after their inventor, "Shakespearian Bridges," will be found at p. 300 of our third volume. The following additional particulars we extract from a recent number of the Calcutta Gazette :

"These (bridges) are, the celebrated Berai torrent-bridge, eighty miles from Calcutta, near Bancoorah, of 160 feet span, by 9 feet 6; the Gooseyturah torrent-bridge, west of Hazareebaugh, 150 clear span, by 9 feet; and that over the Carramnassa River, of 320 feet by 8 feet 9. They are all composed of tarred coir rope, so light as from three to five inches in circumference, and were constructed in Calcutta by the Superintendant-General. That of the Carramnassa, from its magnitude, and the very peculiar circumstances of its situation, appears to have drawn a crowd of spectators from the Holy City of Benares and adjacent country, and is hailed as a boon bestowed on all Hindoos and pilgrims, who are now enabled to pass over the polluted waters equally free of contamination and expense. It is, at the same time, universally admitted, that the projector has succeeded in accomplishing a work of much utility, which has hitherto baffled every effort of power and money. We understand farther, that the Shakespearian bridge is in a fair way, under the auspices of Government, of being generally introduced throughout the inner range of the Hymalayah Mountains. It is peculiarly adapted to the River Sutlej, with high precipitous rocky sides, the width not very great, but the roaring of the torrent tremendous; the forests affording all the materials necessary, at inconsiderable expense, and the simplicity of the construction is such, that the mountaineers themselves will soon learn to set them up without Europeau assistance. When we consider the number of

lives that are sacrificed every succeeding year in passing mountain torrents, by the frail Joolah, and other inefficient methods hitherto in use, and that nei

ther cattle nor merchandize can pass over them, there is great reason to rejoice in the happy introduction, by means the most simple, of an ingenious scheme, in every way fraught with benefit to mankind."

EGYPTIAN ORE.

SIR,-Observing in your really useful publication an inquiry respecting MPhail's Egyptian Ore, I beg to offer my individual testimony as to its merits. I consider it as decidedly the most perfect imitation of gold which has yet been discovered. It will retain its colour as long as the material itself, and the slightest friction of a soft leather will at all times restore its original lustre. It, of course, will not resist the test of aquafortis; this is a criterion which gold alone can endure; but, in every other respect, I believe it to possess all the properties hitherto deemed as exclusively belonging to that metal. I have a watch and chain of his Egyptian ore, to which are suspended two sterling gold seals; and it is a singular fact, that I have frequently placed them in the hands of jewellers and workers in gold, requesting them to distinguish the real from the imitative metal, without applying the test, and in every instance they have been unable to decide.

As it is possible that some of your readers, deeming this a mere anonymous communication, may not attach that credence to my statement which it really deserves, I enclose a few cards of my address, and shall be happy personally to satisfy any inquirers who may deem it worth their while to favour me with a call; and I have made the above statement solely from an anxiety to offer my testimony to the merits of an invention which, I firmly believe, only requires to be more known to be universally patronized.

I am, Sir, yours, &c.

WOODEN CHURCH CLOCKS.

V.

SIR, In answer to your Corre-. spondent, Vittoria (p. 91, vol. iv.),

*Which may be had by applying to our publishers.-EDIT.

« ForrigeFortsett »