rection of the axis ; this is placed ing it? Coals are to be had in abundance with its axis vertical, and is pro- in the vicinity. He would willingly pay vided with a semi-cylindrical case,

any gentleman for proper plans and in

structions. revolving about the same axis, the R. H. has favoured us with the followdiameter of which semi-cylinder is ing reply to Mr. Hall-(See Correspondadjusted to coincide with the dience of last week): rection of the wind. Thus one-half “SIR-My error,in page 309, has served the sails are exposed to the wind,

other purposes besides being amusing : and one-half sheltered, and a ro

for one, it has given me a warning to be

more particular for the future. I now tatory motion is produced.

see the error clearly : how it could escape I am, Sir,

my notice at the time, is more than I can Yours respectfully,

account for. F.O. M

“The following, I believe, will be found correct :- Take the area of both ends,

and a mean proportional between them; No. 134.

add these sums together, and take one

third for the mean area. For instauce, VARNISHING STUCCO IMAGES. from the dimensions given, page 308 SIR,-Having an anxious desire

182 +62 + 182 x 62 :3 = 156 = 13 feet.

“I was aware of this method when I of adding something to the stock of

gave the other; but I imagined that the general knowledge, and having ob- other came near the truth, and by more served several answers to your simple operatious. Terred; I thank Mr. Correspondent Aurum, elucidating H. for pointing out my error; and I now various ways of preserving Stucco give you a method not liable to this ob

jection. Images, I beg permission to offer

“The error of G.A.S. is still conspione more method, and that a very cuous ; aud my proof of the erroneous simple one, but which none of your principle on which it was founded will be able Correspondents have noticed, found correct.

R. H.” probably from its simplicity.

Mr Hope will find the information he I purchased of an Italian, some hased of an Italian some requests at p. 159, vol. iv.

We thank Cesur Borgia for his difmonths ago, the bust of Lord Byron;

ferent hiuts. That respecting the Praxis I kept it until perfectly dry. I we shall very probably follow. His trinimed it from all the superfluous “ New System of Fortification" will be marks left from the mould, and then acceptable. immersed it in raw linseed oil for

A Correspondent, alluding to the “ Air

Balloou of the 17th Century,” says—“! twelve hours (without any prepa.'

caunot help remarking, that long before ration whatever, save the trim. the discovery of Montgolfier, the princining); I then took it out, and ple and practice of the fire balloon were drained the loose oil from it: it knowu in England. There are persons now has the appearance of yellow

alive now at Ringwood, in Dorsetshire,

who remember a doctor in that town that wax. When it gets dirty, or fly.

frequently let them off for his amusemarked, it will clean by washing

meut, twenty years before ever Lunardi it with a sponge and lukewarm ascended in Eugland. I have heard, too, soap and water.

of similar exhibitions before that in ra. I am, Sir,

rious other parts of the kingdom.” Your hunible servant,

A letter from a Correspondent to

“ Mechanicus" is left with our Pub

W. GILKES. : lishers. 73, Whecler-street, Spitalfields,

G. U. A.'s letter did not reach us till 8th Sept. 1925.

after last week's publication. His former paper will appear in next week's


Communications received from--Alpha

-Ben Mizen-Lucidus --C.Smith-H.S. A Correspondent (Tyne), who has -B. P. C.-Amicus-G. H. E.-B. J.lately discoverert a Copper Ore Vein, R. R. which he supposes will yield 200 tons of ore annually, wishes some of our intelligent readers to inform him, what will Communications (post paid) to be addressed to

the Editor, at the Publishers', KNIGHT and be the expense of erecting a Smelling

LACEY, 55, Paternoster-row, London. house, to smelt that quantity of metal, and what would be the expense of suclt.


Printed by Mills, Jowett, and Muis (late
** BENSLEY), Bolt-court, Fleet-street.

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useful in surveying, &c. The outer ACCOUNT OF THE TRIGONOMETER,

Sh; rim of the large quadrant has the A NEW INSTRUMENT, INVENTED

angle in quarter degrees engraven BY MR. M. P. MOYLEY.

on it, and numbered both ways; Sir,- In January, 1824, I trans, and when the instrument is open to mitted to the “ Annals of Philoso- any particular angle from the perphy," some account of an improve- pendicular (say 2610), the inner rim ment of the Clinometer, then gene- of the large quadrant gives rather rally in use for some of the opera- more than 2 feet 11 inches for the tions of mining. It consisted of a length of base,or underlay of a stratum quadrant affixed to it, on which was or lode, supposing the perpendicular engraven the angle at which the to be one fathom. At the same aninstrument might be opened, and gle, if the hypothenuse is one fathe length of base or underlay of a thom, the base would be found, by stratum or lode to a perpendicular the outer rim of the second quadrant, fathom at any particular angle. I to be better than 2 feet 8 inches; at that time stated to Messrs. Knight, and at the other edge the perpenof Foster-lane (who manufactured dicular will be found to be about the instrument for me), as well as 5 feet 41 inches. The reverse sides to many of my friends, that I in- of these quadrants are also gradutended to complete it, by the addi- ated, showing the hypothenuse when tion of another quadrant, on which the perpendicular is given, and the should be graduated the measurement hypothenuse and perpendicular when of the remaining sides of a triangle, the base is given. where one side, and the angle from The instrument is graduated, supthe perpendicular, were given. 1 posing that the radius is in all cases have for some time accomplished six feet, or one fathom; therefore, this; and the prefixed sketch will, I if the side or radius given should be hope, convey an accurate idea of it. two, three, or more fathoms, the I propose calling it a Trigonometer; amount obtained for one must, of for it completes the operation of course, be multiplied by that nummeasuring all kinds of triangles with ber. Caution should always be had the greatest precision and accuracy. that the angle is taken from the per

It consists of two pieces of box- pendicular; and where the angle is wood, AA, firmly united together most conveniently observed from the after the manner of a rule ; each part horizon (as may be the case under is 18 inches in length, and half an peculiar circumstances), the cominch thick; one part is 24 inches in plement of that angle (i. e. what it width, the other 2 inches. To these wants of 90°) must be used, which are occasionally attached two brass will be found to be the same as if the quadrants, II; they are made to angle were had from the perpendislide in and out under the brass čular. This, perhaps, may be more plates, BB, and may be fixed by fully understood by the following the bolts, DD. CCC are three spi- diagram :rit levels, to prove the position of the instrument for various purposes ; E is a small quadrant, divided into degrees only, and numbered both ways. F is a magnetic compass, with its scale divided into 360 degrees, also numbered both ways. This compass is hung by an axis, GG, so that it may always swing horizontally. HHHH are four sights; two are placed on the upper edge of the instrument, and two on the face of the lower half, in a di

rect line with the axis of the com- pass, and which are particularly


403 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, from 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.

Angle 250 will be) ft. in. found to be, for 2 6.42

ft. in. the base., ....)

Angle 250., 5 5.25 Multiplied by .... 6

ft. 15 8.52, base A B.' ft. 33 1,50, perpendicular CB.

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I should hope, from the examples as much may be effected by its use" here given, it will be plain that any in one hour, as has been hithertoi 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, 1,100 sft sefin ment of heights, land-surveying,

Your obedient servant,.,

me ! rettsy 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. Prit,

mason of the country, who was only WILLIAM EDWARDS. ..

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 ani 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."

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