Beginning with those arts which are avowedly the expression of beauty in line, colour, or form, it is easy to show how they were fostered by the religious sense. The inscribed shells and tablets from the mounds of the Mississippi Valley present complex and symmetrical drawings, clearly intended for some mythical being or supernatural personage. Among the Salishan Indians of British Columbia, when a girl reaches maturity she must go alone to the hills and undergo a long period of retirement. At its close, she records her experiences by drawing a number of rude figures in red paint on a boulder, indicating the rites she has performed and the visions she has had.[289] Such rock-writing, or petroglyphs, nearly always of religious import, are found in every continent, and offer the beginnings of the art of drawing. It is possible that the oldest known examples, scratched with a flint on the bones of reindeers dug up in the caves of southern France, may represent the totems or deified heroes of the clan. Certain it is that a class of symbolic figures, which recur the world over, often dating from remote ages, such as the crescent, the cross, the svastika, the triskeles, the circle, and the square, were of religious intention, and conveyed mystic knowledge or supernatural protection in the opinion of those who drew them. The early cultivation of painting in religious art arose chiefly from the symbolism of colours, to which I previously made a passing allusion. Its origin was in the effect which certain hues have upon the mind, either specifically or from association. Colour-symbolism, indeed, forms a prominent feature in nearly every primitive religion. The import of the different colours varies, but not to the degree which excludes some general tendencies. The white and the blue are usually of cheerful and peaceful signification, the black and the red are ominous of strife and darkness. In many tribes the yellow bore the deepest religious meaning. The Mayas of Yucatan assigned it to the dawn and the east; and when the Aztecs gathered around the dying bed of one they loved, and raised their voices in the paean which was to waft the soul to its higher life beyond the grave, they sang: “Already does the dawn appear, the light advances. Already do the birds of yellow plumage tune their songs to greet thee.” These symbolic colours are those with which the early temples were tinted and the rude images of the gods stained. They were rarely harmonious, but they were effective, and appealed to the people for whom they were intended. Their preparation and their technical employment were improved, and, as the art advanced, it reacted on the religion, directing its conceptions of divinity into higher walks and toward nobler ideals.