1892. In sending out this essay, the author asks for indulgence. In the first place, because this is, so far as was known to him, the only attempt to set out, from an architect's point of view, the basis of certain ideas common in the architecture of many lands and religions, the purposes behind the structure and form which may be called the esoteric principles of architecture. And secondly, for an attempt to deal with a subject that could only be rightly handled by one having the equipment of a wide scholarship. Illustrated. Partial Contents: Microcosmos; Four square; At the center of the earth; The Jewel bearing tree; Planetary spheres; Labyrinth; Golden gate of the sun; Pavements like the sea; Ceilings like the sky; Windows of heaven and three hundred and sixty days; Symbol of creation.