OCR Rendition - approximate

286   Art of Travel.

by the eye whereabout it would be in the heavens when its " pointers " were vertical, or due north ; and the Southern Cross is available in precisely the same way. The true North Pole is about 12 degree or 3 diameters of the full moon, apart from the Pole star ; and its place is on a line between the Pole Star and the Great Bear. An almanac, calculated to show the bearing, and the times of moonrise and moonset, for the country to be travelled over, as well as those of sunrise and sunset, would be a very great convenience ; it would be worth while for a traveller accustomed to such calculations to make one for himself.

Diagram.-The diagram (preceding page) is intended to be traced in lines of different colours, when it will be found to be far less confused than at present.

Its object is to enable a traveller to use the sun, both as a rude watch and as a compass. The diagram is calculated for the latitude of London, but will do with more or less accuracy for the whole of England. A traveller going to other countries may easily draw up one for himself, and on a larger scale if he prefers it, by using the Azimuth tables and the Horary tables of Lynn.

The diagram represents, 1st, circles of equal altitudes; 2ndly, the path of sun, stars, &c., for each 10th degree of declination ; 3rdly, the hour angles, all projected down upon -4thly-the level compass card.

Thus, six circles are drawn round the centre of the compass card at equal distances apart, each ring between them representing a space of 15° in altitude.

The following angles were then calculated for each 10th degree of declination in turns, viz.:-The height of the sun, &c., when above the horizon at each point of the compass. 2ndly, the bearing of the sun at each consecutive 'hour. These points were dotted out ; and, by joining the several sets of them, the drawing was made.

The broken lines which diverge in curves from P are hour lines ; those which surround P in more or less complete ovals, are the paths of the sun and stars, for each 10th degree of declination ; the prominent line running from E. round to W. being its path when on the Equator.

).F..- www.fastio.com