keep a perfectly straight course.  But if he cannot find a second mark, it will not be difficult for him to use the tufts of grass, the stones, or the other accidents of the soil, in its place; they need not be precisely in the same line with the mark, but some may be on the right and some on the left of it, in which case, as he walks on the perspective of their change of position will be symmetrical.  Lastly, if he has not even one definite mark, but is walking among a throng of forest trees, he may learn to depend wholly on the symmetry of the changes of perspective of the trees as a guide to his path.  He will keep his point of sight unchanged and will walk in its direction, and if he deviates from that direction, the want of symmetry in the change of perspective on either side of the point on which he wishes to walk, will warn him of his error.  The appreciation of this optical effect grows easily into a habit.  When the more distant view happens to be shut out, the traveller must regain his line under guidance similar to that by which a sailor steers who only looks at his compass at intervals—­I mean by the aspect of the sky, the direction of the wind, and the appearance of the forest, when it has any peculiarity of growth dependent on direction.  The chance of his judgment being erroneous to a small extent is the same on the right hand as on the left, consequently his errors tend to compensate each other.  I wish some scientific traveller would rigidly test the powers of good bushmen and find their “probable” angular deviation from the true course under different circumstances.  Their line should be given to them, and they should be told to make smokes at intervals.  The position of these smokes could be easily mapped out by the traveller.

The art of walking in a straight line is possessed in an eminent degree by good ploughmen.  They always look ahead, and let the plough take care of itself.

To find the way down a Hill-side.—­If on arriving at the steep edge of a ridge, you have to take the caravan down into the plain, and it appears that a difficulty may arise in finding a good way for it; descend first yourself, as well as you can, and seek for a road as you climb back again.  It is far more easy to succeed in doing this as you ascend, than as you descend:  because when at the bottom of a hill, its bold bluffs and precipices face you, and you can at once see and avoid them:  whereas at the top, these are precisely the parts that you overlook and cannot see.

Blind Paths.—­Faintly-marked paths over grass (blind paths) are best seen from a distance.

Lost in a Fog.—­Napoleon, when riding with his staff across a shallow arm of the Gulf of Suez, was caught in a fog:  he utterly lost his way, and found himself in danger.  He there-upon ordered his staff to ride from him, in radiating lines, in all directions, and that such of them as should find the water to become more shallow, should shout out.