Trigonometria Britannica

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Chapter Fourteen


For these other things should be studied most carefully, (if the scheme should be complete and not with an excess of the first generation drawing away from the usage, from [it] being received and made use of) that the whole periphery of the circle being considered most conveniently being cut into 100 equal parts; and all the Canons of Sines, Tangents, Secants, and their Logarithms, together with tables of mean movements and Precessions [of the equinoxes ] with these fractions being displayed. For the sake of these I have decided these few Sines should be adjoining, by dividing the Quadrant into 40 equal parts, of which the number will be able being increased to 200, then 1000, by a third [subdivision] into 5000, and finally 25000. For in the place of Degrees we should use hundredth parts, and for minutes or sixtieths of Degrees, we should use thousandths of the hundredths. Therefor the total Quarter will contain 25 hundredths, and of these any particular thousandths you require.
Note: This is the scheme whereby the circle is to be divided into 100 equal parts or hundredth, and each hundredth to be divided into 1000 equal parts.

Note: Here is the only embodiment of Briggs' scheme referred to in Chapter 1, whereby the circle is divided into 'hundredths' or decimal degrees of size 3.60, and each hundredth into 1000 parts. A second of arc is approx. 0.771605 cross 10-6 part of a the circle, while Briggs' smallest division is 1 cross 10-5 .


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Ian Bruce January 2003