The bark of old trees is generally thicker on the north and northeast sides than on the other sides. A more reliable indicator of direction, though one that a traveler seldom has opportunity to test, is the thickness of annual rings of wood growth, which is more pronounced on the north than on the south side of a tree. This has been noted in widely separated parts of the earth, and has been known for many centuries. More than four hundred years ago it was mentioned by Leonardo da Vinci, that universal genius who was scarcely less celebrated as an engineer and scientist than as an artist and litterateur. "The rings of trees," wrote Leonardo, "show how many years they have lived, and their greater or smaller size shows whether the years were damper or drier. They also show the direction in which they were turned, because they are larger on the north side than on the south, and for this reason the center of the tree is nearer the bark on the south than on the north side." In 1893 this matter was put to a definite test by the New York State Forest Commission, which directed its foresters to examine the regularity of the northward thickening of annual rings in the black spruce of the Adirondacks. The foresters examined 700 trees, of varying exposure, noting in each case the compass-point toward which the longest radius of wood growth pointed. The result was:
Northeast ........... 81
Total north and east.658
Southwest ............ 6
Northwest ........... 8
Total south and west.42
These figures deserve more than a passing glance.
Some plants show a decided polarity in their habit of growth. The compass-plant or rosin-weed (Silphium laciniatmn) that once abounded on the prairies of the Mississippi valley, from Minnesota to Texas, is a conspicuous example. It is a tall plant with long, stiff leaves, that do not grow horizontally but with their edges perpendicular. Its natural habitat is the open, shadeless prairie. If plants are examined that grow thus in the open, especially those in the little swales where they are not fully exposed to fierce winds, it will be found that the great majority of them present their radical leaves north and south. The large flowrer heads on short, thick stems point, like the hemlock's "finger," to the eastward, and show no such tendency to follow the sun toward the west as is characteristic of many plants. I have often used the compass-plant as a guide, and never was led astray by it; in fact, the old settlers on the prairies, if they chanced to get lost on a dark night, would get their bearings by feeling the leaves of the compass-plant.
The closely related prairie dock (Silphium tere-binthinaceum) and that troublesome weed known as prickly lettuce (Lactuca scariola), show a similar polarity. This characteristic is lost if the plants are grown where they receive much shade. Of course, terrestrial magnetism has nothing to do with the polarity of plants; it is the sunlight, received on the two sides of the leaves alternately, that determines their position.
But what think you of plant roots that persistently grow north and south ? The woodsmen of the Great Smoky Mountains declare that there is a "north-and-south plant," as they call it, with two long roots that grow respectively north and south. Doctor Davis of Ware's Valley, on the Tennessee side described it to me as follows: "It resembles wild verbena, grows thigh-high, is a rare plant, and generally is found in hollows on the south side of mountains, in rocky neighborhoods, near trickling streams. Its leaf is serrated, 1 1/2 by I inch, or larger, with purple heart, yellow edges, and the rest a bright red. Its roots usually do grow north and south. The plant is one of the most valuable medicinally that I know of, particularly for syphilitic affections. I do not know it by any other name than the native one of North-and-South. I gather it when I can find it, and use it in my practice." Many others have given me similar reports. I do not know the plant; have never hunted systematically for it.
I am of the opinion that there are natural compass-signs in the forest, and on the plain, that we are ignorant of, but that were well known to savages in a state of nature. Such men, dependent from childhood upon close observation of their environment, but observation urged by entirely different motives from those of our naturalists, and directed toward different ends, would inevitably acquire a woodland lore different from ours, but quite as thorough in its own way. That they should develop keen perceptive faculties is no more remarkable than that a carpenter should hit a nail instead of the thumb that steadies it. That they should notice and study signs that no modern hunter or scientist would bother his head about is a matter of course. Unquestionably we have lost many arts of wildcraft that were daily practised by our ancestors of the stone age, just as we have lost their acquaintance with the habits of animals now extinct. Probably no white man of the future will ever equal Jim Bridger as a trailer; and it is but natural to suppose that Bridger himself had superiors among the savages from whom he learned his craft. It is a superficial judgment to rate as an old-wives' tale every story of exploits in the past that we cannot at present duplicate. However, we need not go to novelists to find out how such things were done. There is much pleasure to be gained in seeking to recover some of the lost arts of a primitive age; and, I believe, some profit as well.
But facts such as I have cited regarding the compass-signs of the woods are of practical value only to men who spend much of their time in the forest, rely wholly on themselves as guides, seldom or never use instruments, and so have their perceptive facilities sharpened beyond any keenness that average sportsmen are likely to acquire. Carry a compass.