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Description, Nature, and General Use

OF THE

SECTOR

:::: AND
PLAIN-SCALE
. Briefly and Painly laid down.

AS ALSO
A Short ACCOUNT

OF THE

U SE S

OF THE

Lines of Numbers, Artificial Sines,

:. and Tangents. stimet

:

The Fourth Edition.

LONDON:
Printed for Tho. WRIGHT, Mathematical Instrument

Maker to His MAJESTY, at the Orrery, neag
Water-Lane, in Fleet-Street, 1746.

ed for TH His fleet-se

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ADVERTISEME NT. THE great Encouragement Mr. Wright

1 has had for above seventeen Years påst, in making large ORRERYS, with the Motions of all the PLANETS and SATELLITEs, and the true Motion of Saturn's Ring, has made him so ready and perfect, that Gentlemen may depend on having them made reasonable and sound, not liable to be out of Order :

As may be seen by one he made for Mr. Watts's Academy in Tower-Street.

Another for His Majesty at Kensington.

Another for the New Royal Academy at Portfmouth.

Another for his Grace the Duke of Argyle, (late Lord Ila.)

And several other large ones for Noblemen and Gentlemen.

He has also great Choice of Mathematical Instruments ready made; as Cases in Silver, Brass or Ivory, Surveying Instruments, Sun-Dials, Weather-Glasses, Reflecting-Telescopes of different Lengths, &c.

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S

X

O METHING concerning the De

scription and Use of the Sector and

Plain-Scale being at this time very

ex much wanted, and so I prefume will be very acceptable, therefore I have compiled this fmall Treatise of them ; in which is briefly. contained, their Description, Nature, and General Use.

In the first Chapter is contained, not only the Description of the Lines upon the Plain-Scale, but likewise their Construction and Nature are therein Bewn: As also a short Account of their Use..

In the second Chapter is contained, the Description of the Sector, and the Lines now commonly placed thereon.

In the third Chapter is rewn, the Ground and General Use of the Sector. From this Chapter it appears, that the Sector ferves as a Scale to ell Radius's, not greater than its Length, when A 2

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