Bearings by Compass, Sun, &c. 287
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° to |
S. 17° |
I |
July |
N. |
23° |
to |
N. ]so |
|
February |
S. |
17 „ |
S. 8 |
|
August |
N. |
18 |
|
N. |
8 |
|
March |
S. |
7 „ |
N. 4 |
|
September N. |
8 |
|
S. |
3 |
|
April |
N. |
5 „ |
N.15 |
|
October |
S. |
3 |
|
S. |
14 |
|
May |
N.15 „ |
N. 22 |
|
November |
S. |
15 |
|
S. |
22 |
|
June |
N.22 „ |
N.23 |
|
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. As to the moon or a star, if its declination be unknown, but its bearing and altitude being given, its declination and path may be found, and therefore the time since its rising or before its setting ; a most useful piece of information to a traveller. Watches break, and compasses cannot be used on horseback without stopping, and therefore a diagram of this description, of which any number of copies can be traced out, may be of use for rough purposes.
Other Signs of Direction.-Bearings by the Growth of Trees.In exposed situations and near the sea, the growth of trees is rarely symmetrical; they betray by their bent heads and stunted branches the direction of the prevalent influences most adverse to their growth. This direction is constant over wide districts in a flat country, but cannot be equally relied upon in a hilly one, where the mountains and valleys affect the conditions of shade and shelter, and deflect the course of the wind.
Moss grows best where there is continuous damp, therefore it prefers that side of a tree which affords the most suitable combination of exposure to damp winds and shelter from the
