I should have mentioned that Russell didn't originally invent the ideological theory of Pyramidology but used it to support the1914 date. Russell plagiarized and drew much of his ideas from other sources and commercialized them for his own means into his published works..
As its known the Pyramid image or symbol is used in Freemasonry, being that so the connection to this ideology and Russell's own theological expressions can be confidently assumed.
Some more info on Pyramidology ....
Charles Piazzi Smyth FRSE FRS FRAS FRSSA (3 January 1819 – 21 February 1900), was Astronomer Royal for Scotland from 1846 to 1888, well known for many innovations in astronomy and his pyramidological and metrological studies of the Great Pyramid of Giza.
Smyth corresponded with pyramid theorist John Taylor
and was heavily influenced by him. Taylor theorized in his 1859 book The Great Pyramid: Why Was It Built? & Who Built It?
that the Great Pyramid was planned and the building supervised by the biblical Noah
Refused a grant by the Royal Society, Smyth went on an expedition to
Egypt in order to accurately measure every surface, dimension, and
aspect of the Great Pyramid. He brought along equipment to measure the
dimensions of the stones, the precise angle of sections such as the
descending passage, and a specially designed camera
to photograph both the interior and exterior of the pyramid. He also
used other instruments to make astronomical calculations and determine
the pyramid's accurate latitude and longitude.
This diagram from Smyth's Our Inheritance in the Great Pyramid (1877) shows some of his measurements and chronological determinations made from them
Smyth subsequently published his book Our Inheritance in the Great Pyramid in 1864 (which he expanded over the years and is also titled The Great Pyramid: Its Secrets and Mysteries Revealed). Smyth claimed that the measurements he obtained from the Great Pyramid of Giza indicated a unit of length, the pyramid inch, equivalent to 1.001 British
inches, that could have been the standard of measurement by the
pyramid's architects. From this he extrapolated a number of other
measurements, including the pyramid pint, the sacred cubit, and the pyramid scale of temperature.
Smyth claimed that the pyramid inch was a God-given measure handed
down through the centuries from the time of Shem (Noah's Son), and that
the architects of the pyramid could only have been directed by the hand
of God. To support this Smyth said that, in measuring the pyramid, he
found the number of inches in the perimeter of the base equalled one
thousand times the number of days in a year, and found a numeric
relationship between the height of the pyramid in inches to the distance
from Earth to the Sun, measured in statute miles. He also advanced the
theory that the Great Pyramid was a repository of prophecies which could be revealed by detailed measurements of the structure. Working upon theories by Taylor, he conjectured that the Hyksos were the Hebrew people, and that they built the Great Pyramid under the leadership of Melchizedek. Because the pyramid inch was a divine unit of measurement, Smyth, a committed proponent of British Israelism, used his conclusions as an argument against the introduction of the metric system
in Britain. For much of his life he was a vocal opponent of the metric
system, which he considered a product of the minds of atheistic French radicals, a position advocated in many of his works.
Smyth, despite his bad reputation in Egyptological
circles today, performed much valuable work at Giza. He made the most
accurate measurements of the Great Pyramid that any explorer had made up
to that time, and he photographed the interior passages, using a magnesium
light, for the first time. Smyth's work resulted in many drawings and
calculations, which were soon incorporated into his books Our Inheritance in the Great Pyramid, the three-volume Life and Work at the Great Pyramid (1867), and On the Antiquity of Intellectual Man
(1868). For his works he was awarded a gold medal by the Royal Society
of Edinburgh, but in 1874, the Royal Society rejected his paper on the
design of Khufu's pyramid, as they had Taylor's. The rejection of his
ideas helped contribute to his resignation from his post as Royal
Astronomer in 1888.
Influence of Smyth's pyramid theories
Smyth's theories on pyramid prophecy were then integrated into the works and prophecies of Charles Taze Russell (such as his Studies in the Scriptures), who founded the Bible Student movement (most visible today in the Jehovah's Witnesses, though Russell's successor, Joseph F. Rutherford, denounced pyramidology as unscriptural). Smyth's proposed dates for the Second Coming, first 1882 then many dates between 1892 and 1911, were failed predictions.
The theories of Taylor and Smyth gained many eminent supporters and
detractors in the field of Egyptology during the late 1800s, but by the
end of the 19th century it had lost most of its mainstream scientific
support. The greatest blow to the theory was dealt by the great
Egyptogist William Matthew Flinders Petrie,
who had initially been a supporter. When Petrie went to Egypt in 1880
to perform new measurements, he found that the pyramid was several feet
smaller than previously believed. This so undermined the theory that
Petrie rejected it, writing "there is no authentic example, that will
bear examination, of the use or existence of any such measure as a
'Pyramid inch,' or of a cubit of 25.025 British inches."