As to the destruction of the Atlanteans in the Tenth Stanza, H.P. Blavatsky noticed that the "Giants" had "not been left without their witnesses." So, let us trace their disappearance through the successive cycles of the Fourth and Fifth Root-Races.
In the 4th Sub-Race of the Fourth Root-Race some 4-5 million years ago, Atlantean civilization enjoyed its heyday. It reigned strong and vibrant but began to crumble due to its errant ways. The seeds of the Fifth Root-Race were dropped in the 4th Sub-Race. These seeds of future humanities remained unnoticeable at first as they lived side by side with the Atlanteans. They remained unnoticed because the racial cycles within overlapping Root-Races refer to the flow of the inner man, not to their outer bodies. The same apparent outer bodies can have a different Root-Race inner man working through them. When the 4th Root-Race fled to Northern Asia to escape the sinking of the great Continent, it carried these Fifth Root-Race seeds. Some Fifth Root-Race seeds were already there from the migrations at the close of the Third Root-Race. These two groups of Fifth Root-Race seeds mixed with some of the surviving Fourth Root-Race Atlanteans, first in Northern Asia and later in Central Asia. The offspring from this mixing were the Mongolo-Turanians (the yellow-white), for lack of a better term. In Collected Writings 13:329, the Turanians were neither "they themselves a pure, primitive race, as it is a mixture of the white and yellow races, and the people who belong to it offer an infinite gradation of hues and types, a gradual descent from the pure European down to the Chinese type." In the 4th Family Race of the 5th Sub-Race of the Fourth Root-Race, the Mongolo-Turanians became noticeably distinct from the surviving Atlanteans. In Dialogues 1:56 and 86, G. de Purucker explained how a future racial cycle becomes sui generis in relation to a previous racial cycle; it becomes recognizable in a small sub-cycle corresponding to it during the previous racial cycle. For example, the seeds for the Fifth Root-Race are sown in the 4th Family Race of the 4th Sub-Race of the Fourth Root-Race, but those seeds will only become distinct in the 4th Family Race of the 5th Sub-Race of the Fourth Root-Race; however, it must be remembered that there is not only one sui generis point in any particular Root-Race. Root-Races are constantly changing. The future Root-Race is also considered sui generis when the previous Root-Race reaches its 7th Sub-Race. The Fifth Root-Race initially becomes sui generis in the 5th Sub-Race of the Fourth Root-Race but more completely in the 7th Sub-Race of the Fourth Root-Race, which eventually collides with the development of the 4th Sub-Race of the Fifth Root-Race. Therefore, the evolution of the 5th, 6th, and 7th Sub-Races of the Fourth Root-Race especially crisscross through the 1st, 2nd, and 3rd Sub-Races of the Fifth Root-Race. The Mongolo-Turanians can be thought of as 1st and 2nd Sub-Race peoples. H.P. Blavatsky referred to them as the "nomadic Caucasian" in Isis Unveiled 1:576.
The 4th Sub-Race continued for a long time since it was the main cycle within the Fourth Root-Race, but the 5th Sub-Race surfaced within it as a single "nascent Aryan race" in Central Asia that eventually divided from its "parent stock" and rushed "asunder to scatter over Europe and Asia in search of new homes" over several million years, per Collected Writings 5:206. From one perspective, the "4th and 5th sub-races" of the "Mongolo-Turanian" and the "Indo-European" in The Secret Doctrine 1:319 belonged to the Fourth Root-Race. H.P. Blavatsky referred to this 5th Sub-Race as the "so-called" Indo-European because portions of the Fourth Root-Race had now become distinct, or more fully Aryanised, in contrast to the Atlanteans. These portions of the distinct 5th Sub-Race of the Fourth Root-Race were the earliest Sub-Races of the Adamite Fifth Root-Race (since the Fifth Root-Race is "hardly correctly" called the "Aryan" in The Secret Doctrine 2:434). Mahatma K.H. spoke of them in Letter 23B in The Mahatma Letters on page154 as "the first sub-race of the fifth root Race." In Collected Writings 12:382, H.P. Blavatsky called these scattered groups the "last offshoot of the first sub-race of the fifth Root-race which is now the dominant one." By calling them the "first sub-race,"she equated the Indo-Europeans with the 5th Sub-Race of the Fourth Root-Race splitting from the Mongolo-Turanian of the 4th Sub-Race of the Fourth Root-Race. By calling them the "last offshoot," she connected them as Indo-Europeans at the close of the 1st Sub-Race of the Fifth Root-Race to the 3rd Sub-Race of the Fifth Root-Race. By calling them the "dominant one," she pointed to the 3rd Sub-Race on its ascent concomitant with the 4th Sub-Race on its descent. While the Mongolo-Turanians can be thought of as belonging to the 1st and 2nd Sub-Races of the Fifth Root-Race emerging from the mid-point of the Fourth Sub-Race of the Fourth Root-Race, the Hindu-Aryans can be thought of as belonging to the 3rd Sub-Race of the Fifth Root-Race and the Indo-Europeans can ultimately be thought of as belonging to the 4th Sub-Race in their full development. H.P Blavatsky referred to these Hindu-Aryans (yellow-white-brown interblending) when she wrote about the Fifth Root-Race becoming "sui generis" some "1,000,000 years"ago in The Secret Doctrine 2:435. In Fountain-Source on page 163, G. de Purucker equated the "Hindu or Aryan race" with "one of the very first subraces of our very own fifth root-race."
In the millions of years of the 4th and 5th Sub-Races of the Fourth Root-Race, the early Sub-Races of the Fifth Root-Race developed in sync from Mongolo-Turanian seeds. The 1st and 2nd Sub-Races of the Fifth Root-Race overlapped the dominant 4th and 5th Sub-Races of the Fourth Root-Race. Shortly before the sinking of the Pacific island Ruta some 850,000 years ago, the 2nd and 3rd Sub-Races of the Fifth Root-Race demonstrated their independence, "moving from one land to the other" in The Secret Doctrine 2:750. While H.P. Blavatsky described the 3rd Sub-Race as more of an "unalloyed" Hindu-Aryan race in Collected Writings 5:216, it was never completely so since it was "largely mixed up with races to which Ethnology gives other names," per The Secret Doctrine 2:429. For example, it was a "hybrid of Hamite and Aryan"in Isis Unveiled 1:576. In her own way, she hinted at this extensive intermingling in The Secret Doctrine 1:113 by linking the Turanians, the Egyptians, the Chinese, and the Chaldeans with the "seven divisions of the Fifth Root-Race" and distinguishing them from the Fourth Root-Race. In fact, these groups belonged to both. Since the Chinese developed as the 7th Family Race of the 7th Sub-Race of the Fourth Root-Race, their language was a little less "ancient than the Egyptian alphabet of Thoth" in The Secret Doctrine 1:307. But through intermarriage the Chinese were "one of the oldest nations of our Fifth Root-Race" in The Secret Doctrine 2:364. All the races of the world are interblended because the Sub-Races on the ascent in a Root-Race overlap with the Sub-Races on the descent in the next Root-Race. As H.P. Blavatsky wrote in Collected Writings 11:388, "the far remote, so-called antediluvian, ancestors of Egypt and those of the Brahmin-Aryans sprang once upon a time from the same stock." The Hindu-Aryan 3rd Sub-Race of the Fifth Root-Race descended onto the world stage about one million years ago just as the Atlantean 7th Sub-Race climbed to its summit prior to Ruta's sinking. This is why H.P. Blavatsky noted in The Secret Doctrine 2:280 that the "highest and last branch of the Fourth Race" reached "their highest civilization when the Fifth had hardly appeared in Asia." That is, the 7th Sub-Race of the Fourth Root-Race developed concurrently with the 3rd Sub-Race of the Fifth Root-Race. We know this because H.P. Blavatsky clarified in The Secret Doctrine 2:436 that the gods, or the Planetary Spirits under the rule of the "three 'Virgins'" or Virgo as the Venus-Mercury connection to Earth's humanity, "abandoned the Atlanteans to their doom" but "returned (or redescended, rather) during the third Sub-Race of the Fifth."
Finally, the Egyptians in their distant ancestry were one of the Atlanto-Aryan peoples on the doomed island of Ruta, per The Secret Doctrine 2:436. After fleeing the sinking Ruta, the ancestral Egyptians separated from their Atlantean predecessors. This separation accelerated with the demise of Daitya (the Indian Ocean island) around 270,000 years ago when multiple chains of islands around Sri Lanka sank over a period of tens of thousands of years, per The Secret Doctrine 2:141. The inhabitants fled in multiple waves to India as well as to northern and eastern Africa. The migrants who colonized Egypt in multiple waves from both Ruta and Daitya to build the pyramids did not belong to the Fourth Root-Race even though they were "Atlanteans." H.P. Blavatsky explained in Collected Writings 5:286, "And though the Egyptians did not belong to the fourth race, yet they were Atlanteans whose islands [ed. Ruta and Daitya] perished still earlier than Poseidonis." William Q. Judge in Echoes of the Orient on page 21 confirmed that we are all "Atlantean monads." G.de Purucker in Studies on page 18 reiterated the sentiment, "There is no such thing as a pure race on the face of the globe. We are all mixed." If the last ripples of the Daitya deluge did not end until 100,000 years ago, as hinted in The Letters on page 238, the Egyptian migrants would have had time to finish their settlements prior to launching into pyramid building by 75,000 BC.
In hindsight, it is apropos to draw attention to H.P. Blavatsky's comments in The Secret Doctrine 2:434 on trying to trace the cycles, "the Races, Sub-Races, etc., etc., down to their smallest ramifications, overlap and are entangled with each other until it is nearly impossible to separate them." She attempted to "express in figures--but only within approximate limits, for the sake of comparison--the duration of time through which it is possible to definitely distinguish one division from another."
Sources:
A.T. Barker, comp., The Letters of H.P. Blavatsky to A.P. Sinnett (Pasadena: Theosophical University Press, 1973).
A.T. Barker, comp., The Mahatma Letters to A.P. Sinnett (Pasadena: Theosophical University Press, 1975).
H.P. Blavatsky, Collected Writings, Vol. 5 (Wheaton: Philosophical Research Society, Inc., 1950).
H.P. Blavatsky, Collected Writings, Vol. 11 (Wheaton: The Theosophical Publishing House, 1973).
H.P. Blavatsky, Collected Writings, Vol. 12 (Wheaton: The Theosophical Publishing House, 1980).
H.P. Blavatsky, Collected Writings, Vol. 13 (Wheaton: The Theosophical Publishing House, 1982).
H.P. Blavatsky, Isis Unveiled (Pasadena: Theosophical University Press, 1998).
H.P. Blavatsky, The Secret Doctrine (Pasadena: Theosophical University Press, 2019).
William Q. Judge, Echoes of the Orient (Pasadena: The Theosophical Publishing Company, 1906).
G. de Purucker, The Dialogues of G. de Purucker (Pasadena: Theosophical University Press, 1948).
G. de Purucker, Fountain-Source of Occultism (Pasadena: Theosophical University Press, 1974).
G. de Purucker, Studies in Occult Philosophy (Pasadena: Theosophical University Press, 1973).
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