Among the remarkable structures of the Mound-Builders, reviewed in a subsequent chapter, their explorers have been struck by the peculiarities of a certain class of mounds, erected on the most elevated summits of outlying hills. Concerning these “there can be no doubt that the ancient people selected prominent and elevated positions upon which to build large fires, which were kept burning for long periods, or renewed at frequent intervals. They appear to have been built generally upon heaps of stones, which are broken up and sometimes partially vitrified. In all cases they exhibit marks of intense and protracted heat.”[64] Such indications have been supposed to mark ancient signal-stations adapted to the telegraphic system still in use among native tribes, of sending up columns of smoke as a warning that enemies are at hand. But this “putting out fire,” as it is called among the Indians of the north-west, for the purposes of signal, is now accomplished by the simple process of setting the short-tufted buffalo grass in flame, and presents slight analogy to the traces of intense fires on the ancient hill-mounds, where the amount of scoriaceous material often covers a large space several feet deep. Perhaps greater importance is due to the employment of the same method of fire-making at the present day among the Indians of the north-west, as we see illustrated in ancient Aztec paintings; while the sun-worshippers of the southern continent had devised a totally distinct method, corresponding to that by which the Romans kindled the sacred fire. Mr. Paul Kane thus describes the process employed by the Chinooks on the Columbia River:—“The fire is obtained by means of a flat piece of dry cedar, in which a small hollow is cut, with a channel for the ignited charcoal to run over; on this the Indian sits to hold it steady, while he rapidly twirls a round stick of the same wood between the palms of his hands, with the point pressed into the hollow. In a very short time sparks begin to fall through the channel upon finely frayed cedar-bark placed underneath, which they soon ignite. There is a great deal of knack in doing this, but those who are used to it will light a fire in a very short time. The men usually carry these sticks about with them, as after they have been once used they produce the fire more quickly.”[65] I witnessed the process successfully employed under the most unfavourable circumstances, on one occasion when camping out with Chippewa guides on the Lake of Bays, in Western Canada. We had struck our tents, and were making our way down the river, when a steady rain set in, which continued throughout the day. We had to pass several long portages, involving in each case the unloading, and carrying over them, our canoes and baggage; and on one of these occasions, finding myself alone with my Indian guide at the foot of a portage where we must necessarily be detained a considerable time, I suggested to him by words