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A new and correct Instrument for describing Ellipses.

Plate XI. fig. 8, represents an improved instrument for describing Ellipses, invented by Mr. Farey. It is similar in principle to the oval chuck of a turning lathe, and it was not known in time by the Editor, to be included in its proper place in this work. It consists of two brass equal circles, A, B, four inches in diameter, adapted to slide over each other, by turning a pinion, K, to produce their required eccentricity for the delineation of an ellipse. When the circles are placed concentric to each other, a brass ink pen filled with Indian ink placed in the socket ¿, and the circles turned round by the small pins at a, a, a, a, between the four straight rulers, D, E, F, G, the instrument will describe a circle on the paper underneath, and of any diameter less than that of the circle according as you turn the pinion, H, or move the socket with the pen b. The two rulers, D, E, apply to the lower circle, and the rulers, F, G, to the upper; when the circles are made eccentric by turning the pinion or nut, K, the pen will describe an accurate ellipse, the eccentricity of which may be increased as required, by simply turning the nut, K, for an increased separation of the circles. Another ellipse, parallel to the first, may if required be readily described by loosening the two screw nuts, N, O, to move the centre frame, and setting the pen opposite to the ruler D, the frame and circles may be moved with the longer axis parallel to itself, so as to describe another parallel ellipse.

This is a property very advantageous to an engraver or other artist, as he is enabled to represent in perspective the thickness of a circular plate, &c. &c. A pair of small jointed ink drawing bows, such as is usually contained in a common case of drawing instruments, is a very convenient and useful article to place in the socket b; if a long arm containing a pen is occasionally placed in the socket b, an ellipse tolerably correct for purposes of delineation on paper of a diameter beyond the size of the instru ment can be drawn.

A more complete description by Mr. Farey, is given with the instrument, and may be seen in the Transactions of the Society of Arts for 1812. The whole instrument is contained in a pocket fish-skin case, 6 inches square and 1 inch deep.

A LIST

Of the principal Instruments described in this Work, and their Prices, as made and sold by W. and S. JONES, 30, Holborn, London.

PLATE I.

PARTIAL, or complete magazine cases of instruments, as represented in the plate, from 17. 18s. to.....

PLATE II.

Parallel rulers, fig. A, B, C, D, and E, according to

£. s. d.

10 10 0

the length and mounting, from 2s. each, to ...... 2 12 6

N. B. Of figs. A, or B, or C, or D, or E, one of them

is included in the cases above, to order.

Improved ruler, FGH

Ditto I KL ..

1 11 6

Ditto represented at M, from 10s. 6d. to

1 16 0

0 16 0

PLATE III.

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090 Fig. 1. Marquois's parallel scales, divided.......... 2 and 3. Protractors, wood or ivory, from 2s. to 0 7 0 4. Sectors of box-wood, ivory, or brass, &c. according to the length, from 2s. 6d. to 7. Brass proportional compasses, six inches.... Without the adjusting rod, fig. A, plate 1 ..

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....

313 6

1 18 0

1 11 0

9 and 9 a. Elliptical sector, and beam compasses 3 13 6
10. Beam compasses from 17. 4s. to
11. Sisson's beam compasses

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Bevel, &c. rulers, figs. 4, 12, 15, 16, 17, and 18,

various prices from 10s. 6d. to.

3 13 6

PLATE XI.

Fig. 1. Suardi's geometric pen ....

Ditto, with a greater variety of wheels, &c.. 7 7

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4 4 0

Ο

212 6

212 6

Fig. 4. Parabolic drawing machine....

- 5. Cyclograph for drawing circles of large radii

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6. Spiral machine....

7. Protractor, perpendicular, &c.

8. Farey's new elliptical instrument.

PLATE XIV.

Fig. 1. King's surveying quadrant with sights..
2. Portable surveying brass cross and staff..
3. Brass pocket box cross and staff.
Ditto without a staff....

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6. Ditto with a compass and staff.

Ditto with a divided nonius and limb

4. Optical square..

5. Ten inch common theodolite and staves. -7. Best complete portable theodolite....

PLATE XV.

Fig. 1. Common circumferentor and staves
Ditto, without staff.....

--

2 and 6. Improved ditto, with staff, 47. 14s. 6d. to
3. Miner's compass without telescope, 11. 5s. and
4. Four inch pocket common theodolite and staves
5. Six inch theodolite by rack work and staves..
Ditto without rack work, common..

PLATE XVI.

Fig. 1. Second best 7 or 8 inch theodolite and staves,

--

167. 16s. and.......

2. Very best improved ditto, ditto.

Eight inch ditto

Nine inch ditto...

...

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...300 0 0

N. B. For large theodolites see the frontis

piece, from 801. to.....

PLATE XVII.

Fig. 1. Plane table and staves in a box..

-

2. Beighton's improved ditto

3. Spirit level of the best kind with telescope
and staves, according to the adjustments
and finishing, from 81. 8s. to

Common ditto, without compass, from 37. 13s.

6d. to

4. Six inch circular protractors, 17. 18s. to
5. Ditto by rack work, very best...

...

Common circular brass protractors, 6s. to...
6. Perambulator, or measuring wheel, best
8. Way wiser for carriages, 67. 6s. to
9. Station staves, the pair

...

44 0 880

13 13 0

6 6 0 210 O

44 0

0 18 0

7 17 6

15 15 0

2 15 0

Fig. 10. Pocket spirit levels, from 10s. 6d. each, to..

--

11. Improved universal ditto

PLATE XIX.

....

E. s. d.

I 11 6

14 14 0

Fig. 1. Hadley's quadrant, ebony and brass, 37. 10s. to 4 4 0 4. Best metal sextant, 8 to 10 inches radius 13. Brass stand and counterpoise for a ditto Second best sextants, 87. 8s. to

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11. Pocket box sextant from 31. 3s. to
12. Artificial horizon 17. 18s. and complete

PLATE XX.

....

5 5 0 10 10 0

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Fig. 2. The new universal map-meter, 17. 10s. to... 212 6

PLATE XXII.

Fig. 2. Feather edged 12 inch box plotting scales,

each....
Ditto ivory, each

036

0 10 0

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Fig. 2, 3, 4, and 5. Keith's improved box parallel

scales in a case....... Ditto in wood and ivory, or all ivory....

6 and 7. Gunner's callipers, from 21. 2s. to

8. Gunner's quadrant...

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9.

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For farther particulars see W. and S. JONES's general catalogue.

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PLATES

TO THE

GEOMETRICAL

AND

GRAPHICAL ESSAYS,

BY THE LATE

GEORGE ADAMS,

MATHEMATICAL INSTRUMENT MAKER TO HIS MAJESTY, &c.

THE FOURTH EDITION,

CORRECTED AND ENLARGED

BY WILLIAM JONES, F. Am. P.S.

LONDON:

Printed by C. Baldwin, New Bridge-street;

FOR, AND SOLD BY, W. AND S. JONES,
30, HOLBORN.

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