To make a bark cover watertight, it is necessary to coat all seams and to cover all "sewing" with a waterproof material, of which the most favored by the Indians was "spruce gum," the resin obtained from black or white spruce (_Picea mariana_ or _P. glauca_ (Moench) Voss). The resin of the red spruce (_Picea rubens_ Sarg.) was not used, so far as has been discovered. The soft resin was scraped from a fallen tree or from one damaged in summer. Spruce gum could be accumulated by stripping a narrow length of bark from trees early in the spring and then, during warm weather, gathering the resin that appeared at the bottoms of the scars thus made. It was melted or heated in various ways to make it workable and certain materials were usually added to make it durable in use. [Illustration: Figure 8 Stone axe] The most important aids to the Indian in canoe construction were his patience, knowledge of the working qualities of materials, his manual skill with the crude cutting, scraping, and boring instruments known to him, and of course fire; time was, perforce, of less importance. The canoe builder had to learn by experience and close observation how to work the material available. The wood-working tools of the stone age were relatively inefficient, but with care and skill could be used with remarkable precision and neatness. Felling of trees was accomplished by use of a stone axe, hatchet, or adze, combined with the use of fire. The method almost universally employed by primitive people was followed. The tree was first girdled by striking it with the stone tool to loosen and raise the wood fibers and remove the soft green bark. Above this girdle the trunk was daubed all around with wet earth, or preferably clay. A large, hot fire was then built around the base of the tree and, after the loose fibers were burned away and the wood well charred, the char was removed by blows from the stone tool. The process was repeated until the trunk was cut through enough for the tree to fall. The fallen trunk could be cut into sections by employing the same methods, mud being laid on each side of the "cut" to prevent the fire from spreading along the trunk. Fire could also be used to cut down poles and small trees, to cut them into sections, and to sharpen the ends into points to form crude wedges or stakes.