In his early investigations on the principles of construction of the Great Pyramid, the author was forcibly struck with the following fact—viz., that if a perpendicular be drawn through the apex of the Pyramid to its base, and the unit angle with the horizontal thrown up from the base on each side of this perpendicular, the angle comes out on the faces of the Pyramid at the openings of the north and south ventilating air-channels; at the same time he was led to the conclusion that one-tenth of the base line, and the same tenths also applied to the faces of the Pyramid, ruled the entire structure.