or it may be found with equal ease, by taking each figure (beginning at the left hand or index), from 9, except the last or right-hand figure, which must be taken from 10. Thus: if from 9.99990 we take 9.35752

It gives 0.64248

die object of this being to perform each problem by addition, in lieu of the lengthy process otherwise required.

Example.—Required the zodiacal longitude and latitude of Halley's comet, at noon, on the 18th October, 1835, Greenwich mean time ?

Comet's right ascension, 16h 25.31 equal in degrees to 246® 19', which, being more than 180°, is south. The declination is 0° 35' north.

Co-tangent dec.


« 11.99219

Sine R.A. from

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