“5…(continued)
Every new Round develops one of the Compound Elements. Thus the First Round, we are taught, developed but one Element, and a nature and humanity in what may be called one aspect of Nature.
The Second Round brought forth and developed two Elements – Fire and Air – and its humanity adapted to this condition of Nature (if we can give the name Humanity to beings living under conditions unknown to men).
The centers of consciousness (destined to develop into humanity as we know it) of the Third Round arrived at a perception of the third Element Water.
Those of the Fourth Round have added earth as a state of matter to their stock as well as the three other elements in their present transformation.
None of the so-called elements were, in the preceding Rounds, as they are now. The elements, whether simple or compound, could not have remained the same since the commencement of the evolution of our chain.
Everything in the Universe progresses steadily in the Great Cycle, while incessantly going up and down in smaller cycles.
Nature is never stationary during Manvantara, as it is ever becoming, not simply being; and mineral, vegetable, and human life are always adapting their organisms to the then reigning Elements, and therefore those Elements were then fitted for them, as they are now for the life of present humanity.
It will only be in the next, or fifth, Round that the fifth Element, Ether – the gross body of Akasa, if it can be called even that – will, by becoming a familiar fact of Nature to all men, as air is familiar to us now, cease to be as at present hypothetical, and also an “agent” for so many things.”
H. P. Blavatsky
The Mark Of God: Understanding Your "I AM Presence" 