This is a book written by Annie Besant and C.W. Leadbeater, who were all members of the Theosophical Society based in Adyar, India. Besant was at the time the President of the Society having succeeded Henry Olcott after his death in 1907. The book consists both of coordinated and illustrated descriptions of presumed etheric counterparts of the atoms of the then known chemical elements, and of other expositions of occult physics.