The diagram, when it is traced out for use, should have the names of the
months written in coloured ink on either side of the south line at places
corresponding to the declination of the sun during those months: viz.:--
January S. 23 degrees to S. 17 degrees
February S. 17 " S. 8
March S. 7 " N. 4
April N. 5 " N. 15
May N. 15 " N. 22
June N. 22 " N. 23
July N. 23 " N. 18
August N. 18 " N. 8
September N. 8 " S. 3
October S. 3 " S. 14
November S. 15 " S. 22
December S. 22 " S. 23
To use the card.--Draw a broad pencil line, which may afterwards be
rubbed out, corresponding to the date of travel, and there will be no
further confusion.
Then, to know what o'clock it is, "span out" (see "Spanning") roughly the
altitude of the sun. The point in the diagram where the altitude so
obtained crosses the pencil mark, corresponds to the position of the sun.
The hour is then read off; and the compass bearings on the diagram are
adjusted by holding it level, and turning it round until a line, drawn
from its centre through the point in question, points towards the sun.
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