Black for Inscriptions is made by mixing lamp-black (which see) with some kind of size, grease, wax, or tar.  Dr. Kane, having no other material at hand, once burnt a large K with gunpowder on the side of a rock.  It proved to be a durable and efficient mark.  When letters are chiselled in a rock, they should be filled with black to make them more conspicuous.

Blood leaves a mark of a dingy hue, that remains long upon a light-coloured, absorbent surface, as upon the face of sandy rocks.

ON FINDING THE WAY.

Recollection of a Path.—­It is difficult to estimate, by recollection only, the true distances between different points in a road that has been once travelled over.  There are many circumstances which may mislead, such as the accidental tedium of one part, or the pleasure of another; but besides these, there is always the fact, that, in a long day’s journey, a man’s faculties of observation are more fresh and active on starting than later in the day, when from the effect of weariness, even peculiar objects will fail to arrest his attention.  Now, as a man’s recollection of an interval of time is, as we all know, mainly derived from the number of impressions that his memory has received while it was passing, it follows that, so far as this cause alone is concerned, the earlier part of his day’s journey will always seem to have been disproportionately long compared to the latter.  It is remarkable, on taking a long half-day’s walk, and subsequently returning, after resting some hours, how long a time the earlier part of the return journey seems to occupy, and how rapidly different well-remembered points seem to succeed each other, as the traveller draws homewards.  In this case, the same cause acts in opposite directions in the two journeys.

To Walk in a Straight Line through Forests.—­Every man who has had frequent occasion to find his way from one place to another in a forest, can do so without straining his attention.  Thus, in the account of Lord Milton’s travels, we read of some North American Indians who were incapable of understanding the white man’s difficulty in keeping a straight line; but no man who has not had practice can walk through trees in a straight line, even with the utmost circumspection.

After making several experiments, I think the explanation of the difficulty and the way of overcoming it are as follows:—­If a man walks on a level surface, guided by a single conspicuous mark, he is almost sure not to travel towards it in a straight line; his muscular sense is not delicate enough to guard him from making small deviations.  If, therefore, after walking some hundred yards towards a single mark, on ground that preserves his track, the traveller should turn round, he will probably be astonished to see how sinuous his course has been.  However, if he take note of a second mark and endeavour to keep it strictly in a line with the first, he will easily