On the History of Gunter's Scale and the Slide Rule During the Seventeenth CenturyCajori, Florian
History
On the History of Gunter's Scale and the Slide Rule During the Seventeenth Century
Cajori, Florian
Slide-rule
Thirdly, opposite to those Sines on the other side are the Logarithmall
Tangents, noted alike both in the moveable and fixed thus
6.6.7.7.8.8.9.9.10.10.15.15.20.20. &c. unto 45.45. which numbers or
divisions serve also for their Complements to 90. so 40 gr. stands for
50. gr. 30. gr. for 60 gr. 20. gr. for 70. gr. &c. each degree here both
in the moveable and fixed is also divided into parts. As for the degrees
which are under 6. viz. 5.4.3.2.1. they are noted with small figures over
this divided Circle from 45.40.35.30.25. &c. and each of those degrees
divided into parts by small points both in the moveable and fixed.
Fourthly, on the other edge of the moveable on the same side is another
graduation of Tangents, like that formerly described. And opposite unto
it, in the fixed is a Graduation of Logarithmall sines in every thing
answerable to the first descrition of Sines on the other side.
Fifthly, on the edge of the Ring is graduated a parte of the Æquator,
numbered thus 10 20. 30. unto 100. and there unto is adjoyned the degrees
of the Meridian inlarged, and numbered thus 10 20.30 unto 70. each degree
both of the Æquator, and Meridian are subdivided into parts; these two
graduated Circles serve to resolve such Questions which concerne
Latitude, Longitude, Rumb, and Distance, in Nauticall operations.
Sixthly, to the concave of the Ring may be added a Circle to be elevated
or depressed for any Latitude, representing the Æquator, and so divided
into houres and parts with an Axis, to shew both the houre, and Azimuth,
and within this Circle may be hanged a Box, and Needle with a Socket for
a staffe to slide into it, and this accommodated with scrue pines to
fasten it to the Ring and staffe, or to take it off at pleasure.
The pages bearing the printed numbers 53-68 in the Grammelogia III, IV and
V make no reference to the dispute with Oughtred and may, therefore, be
assumed to have been published before the appearance of Oughtred’s Circles
of Proportion. On page 53, “To the Reader,” he says:
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