Our third expedition completed the number of logs we required for the log cabin.  Two large 12-foot logs were chosen for the foundation logs at the front and rear of the building.  The logs were flattened along the bottom so that they would have a firmer bearing on the ground, and particularly on the corners, where they rested on foundation stones.  Each log was now notched about a foot from the ends.  The notches were 8 inches long and about 2 inches deep.  Care was taken to place those on one log squarely opposite the notches on the other.  A pair of 14-foot logs were now laid across the foundation logs and rolled along them until another half-turn would have dropped them into the notches (shown in Fig. 266).  Then notches were cut in the 14-foot logs to correspond, so that when the final half-turn was given one notch would fit over the other, making a mortise joint (Fig. 267).  When the side logs were in position notches were cut in their upper surface to receive a pair of 12-foot logs which were rolled onto them, notched and dropped into place.  Then another pair of side logs were laid on, and so the work progressed.  The notches in each log were cut to a depth equal to one-quarter the diameter of the log; that is, if the log was 8 inches in diameter the notch was made 2 inches deep, and if 6 inches in diameter it was cut to a depth of 1-1/2 inches.  When the logs were laid in place no space intervened between them, as will be clearly understood by reference to Fig. 268.

We found, after a few logs had been set in place, that our cabin was growing faster at one end than at the other.  The trouble was that our logs were not of uniform diameter throughout and we had been laying the butt ends, which were larger, all at one end of the building.  So we had to take down the logs and relay them with the butt end of the front foundation log at one end and that of the rear foundation log at the other.  Then the cross logs were laid on with their butt ends on the small ends of the foundation logs.  The next end logs were laid with their small ends on the butt ends of the cross logs, and so on, taking care never to lay the butt end of one log across the butt end of another.  In this way the walls were built up evenly to a height of 3 feet.

[Illustration:  Fig. 269.  Piece Cut Out to Admit Saw.]

We had planned to make a large open fireplace in the cabin, and this necessitated cutting an opening in the rear wall.  But we did not want to cut the opening until the wall was built up to its full height lest it might buckle while the remainder of the logs were being placed in position.  So we merely cut a piece out of the top log to make room for a saw when we were ready to cut the complete opening.  As our fireplace was to be 5 feet in width, a 5-foot piece was cut out of the center of the log.  Then the ends were supported by cleats nailed on each side, as shown in Fig. 269.  This done the building was continued as before, but as the walls grew we