Picture writing can not be said to be much practiced by any of these tribes, though it is to some extent by all, principally by the Crow and Sioux Indians. The former of these nations are incessant in the war expeditions against the Blackfeet, and in the absence of the warriors the camp from which they departed moves in quest of game, but pursue a direction made known to the warriors before they leave. It often happens that the trail made by the camp is effaced by rain or covered with snow before their return, also that they (the camp) are obliged to diverge from the route agreed upon, and in these cases leave intelligence in pictorial devices in some of their encampments as guides to the returning absentees, who, if they find them, can not fail to reach their friends by following the instructions pointed out by these means. (Fig. 35.) Another occasion where it is useful is where a war party, after having made an attack, whether successful or not, have reason to believe more of their own people are out for like purposes, wish to convey to them the intelligence that their enemies are on the alert, and prevent if possible their falling into their hands, as would happen if they attempted to steal the horses before the late excitement caused by their own appearance had subsided. The information, together with the success or failure of their own expedition and any other matters they wish their friends to know, are pictured in some place likely to be found by those for whom it is intended. [Illustration: FIGURE 35.—Picture writing. Key: “We are a camp of 13 lodges (1); encamped on a creek above the forks (2); started hunting with eight horsemen (3); and two women on foot (4); slept two nights out (5); found buffalo beyond the second creek from the camp (6); killed some, and made travails (7); and slept but one night on our return home (8)]