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If the perpendicular, AC, is one fathom, and it is found, by placing

EXAMPLE I. the instrument at A, that the angle, AB, is 40°, it will instantly show that the base, CB, or underlay of AB, supposing it a stratum or lode, will be about five feet and nearly half an inch, while the length of the hypothenuse, AB, will be 7 feet 10 in. nearly. But if the instrument cannot be, so placed, but that we can either first place it level, at B, and then, by means of the sights, raise it so as to intersect A, the angle will be found to be 50°. So also would it be if the instrument was placed on the surface of the declination at A, and the other half raised to a level, as shown by the dotted line. In either case the complement of this Given, the angle C, froin the perangle must be used, which will be pendicular, 25°, and hypothenuse found to be 40°, as before.

AC, six fathom, or 36 feet; the perI shall now endeavour to exemplify pendicular, CB, and base, AB, are its utility more fully by a few ex- required. amples.

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ft. 63 1.44, hyp. AC,

ft. 40 11.92, base AB.

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I should hope, from the examples as much may be effected by its user here given, it will be plain that any in one hour, as has been hitherto triangle may be accurately measured; done by the common methods in consequently its application may be twenty-four. extensively used for the measure

I am, Sir, ment of 'heights, land-surveying,

Your obedient servant, and every species of dialling required in the most intricate operations; and

M. P. MOYLEY.,, I find, from actual experiment, that Helston, Aug. 1, 1825.


mason of the country, who was only

indebted for his skill to his own inOne of the most extraordinary dustry and the power of his genius! bridges in Great Britain is that over He had engaged, in 1746, to build a the river Taff, near Llantrissent, in new bridge at this place, which he Glamorganshire, called in Welsh executed in a style superior to any Pont y ty Prydd. This was the work thing of the kind in this or any part of William Edwards, an uneducated of Wales, for neatness of workman


405 ship and elegance of design. It con- it is made widest at the abutments, sisted of three arches, elegantly light from which it contracts towards the in their construction, and was ad- centre.-PercyAnecdotes of Industry. mired by all who saw it. Unfortunately a great flood which occurred drifted down a quantity of timber against the bridge. In consequence STRENGTH OF LEADEN PIPES. of this obstruction to the flood, a thick and strong dam, as it were, was formed. The aggregate of so

[From the Caledonian Mercury.] many collected streams being unable to get any further, rose here to a Some curious and interesting expeprodigious height, and with the force riments on this point have recently of its pressure carried the bridge en- been made by Mr. Jardine, engitirely away before it. William Ed. neer, at the Water Company's Yard in wards had given security for the sta

Heriot's Green, Edinburgh, with the bility of the bridge for seven years ;

view of determining accurately the it had stood only two years and a

proper strength or thickness of metal half. Of course he was obliged to conveying

water through different parts

to be given to the pipes intended for erect another; and he proceeded on of the city. This is an important subhis duty with all possible speed. The ject, and one regarding which pracsecond bridge was of one arch, fortical men have hitherto been much in the purpose of admitting freely under the dark. The observations, thereit whatever incumbrances the floods fore, set on foot by this distinguished might bring down.

The span or

engineer cannot fail to be of great utichord of this arch was 140 feet, its lity, and we hope the particulars of altitude 35 feet, the segment of a

them will be communicated to the circle whose diameter was 170 feet. public ; for it happens in this, as well

as in many other branches of mechaThe arch was finished, but the para- nics, that a few judicious and careful pets not yet erected, when, such was

experimeuts, in one or two particular the pressure of the unavoidably pon- instances, are sufficient to comprehend derous work over the launches, that a vast variety of cases which are conit sprung in the middle, and the key tinually occurring in practice. The stones were forced out. This was a strength of pipes, for example, even severe blow to a man who had his those of the same thickness of metal, therto met with nothing but misfor

varies greatly with the calibre of each. tune in an enterprise which was to actly as its calibre, or internal diame

The pipe, in fact, becomes weaker exestablish or ruin him in his pro- ter, is enlarged. Hence it is quite un'fession. William Edwards, however, necessary to make trials of all the difpossessed a courage and a confidence ferent sizes of pipes, as one good obhis

powers which never forsook servation of any particular diameter him; he engaged in the work a third and thickness of metal affords a rule time, and, by means of cylindrical for computing the comparative strength holes through the haunches, so re

of pipes of any other dimensions whatduced their weight, that there was

The following are the results of

two of the above experiments. no longer any danger from it. The second bridge fell in 1751; the third, this--the pipe to be tried is closed at

The manner of making the trial is which has stood ever since, was com- one extremity, while the other commu. pleted in 1761. The present arch is nicates with a forcing pump, by means 140 feet in span, and 35 feet high, of which water is thrown into it and being the segment of a circle of 175 forced, until it presses the pipe on all feet in diaineter. In each haunch sides with a violent pressure, in the there are three cylindrical openings

same manner as if the pipe were conrunning through' from side to side; veying the water of a lofty spring, the

effect of which is to press out the pipe the diameter of the lowest is nine

on all sides in proportion to the height feet; of the next, six feet; and of of the fountain-head. But the pump the uppermost, three feet. The is also furnished with a valve or guage width of the bridge is about eleven which measures exactly the degree of feet. - To strengthen it horizontally, pressure communicated to the pipe, so




LIGHTING STEEPLE CLOCKS. that; in every experiment, we can com- the metal being much less ductile. pute the height of the reservoir wbich Such is the extreme pressure which would have caused a similar pressure these pipes will bear before bursting, by the water conveyed from it, and in hut it would be unsafe io practice to this manner obtain a rule for adapt subject theni to more than one-third of ing the strength of each pipe to the this. Still, however, it appears that a pressure which its situation subjects it two-inch pipe, with one-fifth of an inch to. When the water from the pump thickness of metal, will be sufficient first begins to press out the pipe, little for withstanding a pressure of 300 feet. or no alteration is observed on it for Many other examples might be given some time, as the operation of forcing of the application of these experiproceeds, however, and the pressure ments, did our limits permit. We thereby becomes increased, the pipe shall just mention, however, an intergradually swells through its whole esting piece of antiquity, which was length, until at last a small protu- lately brought from Italy hy Professor berance is observed rising in some weak Leslie; it is a Roman lead pipe, suppart, which coutinues increasing until posed to have been used in conveying the substance of the metal, becoming

water to the baths of one of the Emgradually thinner and thinner, is at perors; it is not truly round, but of an last fairly rent asunder, when the pipe irregular oval or flattened shape, the bursts with a crash, and the water, metal appearing to have been turned issues with great violence. In the first over longitudinally, without any roller experiment the pipe was 14 inch bore, or niandrel, and then strongly soldered. aud the metal, which was remarkably It is, as near as we recollect, about 25 soft and ductile, was one-fifth of an inches diameter one way, and 2 ipches inch in thickness. This was forced, as the other, and the metal about threeabove described, until the pressure be-, fourths of an inch thick. Now, it is came equivalent to that of a spring or

evident from the above experiments, column of water 1000 feet high, which that the strength of this pipe is enuris equal to 30 atmospheres, or 420lbs. mously above what the occasion could on every square inch of the pipe. This require, and this shows the advantage it sustained without alteration, but with of having accurate experiments to a pressure equal to 1200 feet it began direct the construction of such works. to swell, and with 1400 feet, or 600ībs. on the inch, it burst. It appears surprising that the soft material of lead should sustain so enormous a pressure,

LIGHTING STEEPLE CLOCKS. but this arises from its being equally distributed through every part of the illumined by gas, may be rendered

The face of a Steeple Clock, mass. There is no cross strain nor unequal action in different parts of the equally readable by the inhabitants pipe, but a fair stretch throughout the in the night as in the day; this has whole surface, which it is well-known now, for some years, been exemis by far the most favourable situation plified at the Tron Church, in the for strengih. On measuring the above City of Glasgow. A gas-lantern, pipe after the experiment, it was found whose exterior (except on the side to have swelled out from 14 inch to 13,

next the steeple, where it is glazed) so that a part of the original pipe, w

which had not been subjected to any pressure; the phænir, is supported at several

tastefully represents the bird called could be inserted within the fractured feet distant from and level with the piece. The fracture of this piece presented a very striking appearance. The upper part of the clock-face, by tivo edges were no way ragged, but quite supports acting braceways to each smooth and sharp, like a knife, show-other, and steadied, laterally, by two ing how the metal had been gradually chains proceeding from the corner's distended and thioned out to nothing of the steeple: the main of these by the internal pressure, as if the pipe supports is the gas-pipe, which suphad consisted of soft clay or wax.

In the second experiment, the pipe was

plies the lantern, and the other is two inches diameter and one-fifth of an

also a gas-pipe used for lighting the inch in thickness of metal : this sus

lantern. It effects this by means of tained a pressure of a column 800 feet numerous equidistant small holes, in height with hardly any swelling, but or narrow cross slits in its side, and with 1000 feet it burst. The fracture is called the flush-pipe. At sun-set, here was not so fine as in the other, when the lantern is to be lighted,


407 the lamp - lighter, by means of day : one shilling :: 251, for 219 cocks fixed within his reach in the days : 15 shillings. street; turns the gas into both these I observed the trifling omission I pipes, and, after waiting a proper had made, in not stating the rale; time for the gas to ascend to the and in my letter, which I wrote, and lantern, he applies his flambeau to sent a few days after, containing the the jet of gas issuing from the low- 5 per cent. method (inserted p. 339, est of the holes in the flash-pipe, the vol. iv.), I requested that it might flame from which instantly commu- be noticed. nicates to the jet next above it, and

Yoir Correspondent has been so on, until in a few moments this chain of flame enters the lantern,

pleased in Number 105) to bring and lights the burner of the main

the fractional parts, named by me,

to a common denominator, and call it pipe, which being perceived by the

a solution of the question ! and in illumination on the clock-face, the the beginning of this letter, he makes flash-cock is then turned off, and no

an observation upon my remark of further attendance is needed until about sun-rise, when the other cock

reducing the answer from shillings is shut off, and this clock-lantern

and pence, to pounds, shillings, and

ern pence, by dividing by 20, there being extinguished, in its turn, with those

se a misprint of “or” pence for and in the adjacent street. The lantern

pence. is curiously glazed, convexly, in five panes; and a number of plane mir

As a preliminary step to iny solu. rors are, concavely, fixed behind the

tion of it, I will inform him, that it burner, to act as a reflector in throw

is easier to find the interest at 31. 13s. ing the light principally on the clock

per cent. than at any other rate.

Now, I believe it is well known, that face.

if any sum, the interest of which is

required at 5 per cent. for one day, CALCULATION OF INTEREST. be divided by 7300, the quotient will Sir,-In Number 105 of your va

be the answer; and at 4 per cent., luable Magazine, I observe a com

if by 925. And I find, upon the munication respecting the Calcula.

same principles, that interest at tion of Interest; and from it, it ap

31. 13s. per cent. is procured by dipears, that what was written by your

viding by 10,000. Correspondent, and published in

The difference between 5l. and Number 93, was to refute, and not

31. 13s. is 27 shillings, and between to support, the opinion, that if the 11. and 31. 135., 7 shillings. Let us product of pounds, multiplied by take the fractional parts of 73 shildays, be divided by 3651., the answer lings, which, when added, shall be would be given in shillings. The equal to 7 shillings. I shall take for idea, that it was a letter in refutation, instance (but, of course, many others never crossed my mind : because I may be chosen), 1-12th, 1-80th, and knew that the rule (though by no 1-17,500dth; and I find that, when means a short one) was quite correct; these parts are added to 31. 13s. the and, by consequence, I was misled. amount is 41. and a very sınall fracIn that part of his letter which is ex- tion. Thus, - 73 shillings. pressed thus:-365 days : 219 days

1-12th = 6.0833333 : : 251. : 151., I really imagined he 1-80th = .9125 was showing, that if 365 days were 1-17,500dth = .0011714, &c. used for a divisor, the quotient would be the ansiver in pounds, instead of . Shillings - 80.0000047 shillings; and which appeared to me. As 17,500 appears to be an 'awk- to be, what it really is, nonsense. ward sum to divide by, if it be quaInstead of his proving the fallacy of drupled, the sum will then he 70,000 the rule, as he has imagined, I will (which in dividing, &c. is the same, prove, and I hope to his satisfaction, as to trouble, as by 7); but care that his letter is fallacious; and that must be taken to quadruple its 100, very briefly, viz.-3651. for one quotient.

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