what is the historical origin of the letter G in the east and how do preston and mackey explain its symbolic meaning

The letter G entered lodge usage in the early 18th century as a designation for Geometry, recorded in early exposures and catechisms as the fifth science upon which Masonry is founded, a paper read before Quatuor Coronati Lodge notes. Ritual and lecture assign it a dual primary import: Geometry as the operational foundation of the Craft, and God as the Grand Architect of the Universe.

Mackey observes that the explanation of the letter G has never been an esoteric secret, as the letter itself has always been exposed to public view as part of the lodge's furniture 1. Citing early writers such as William Hutchinson, Frederick Dalcho, and George Oliver, Mackey shows that Masonic authors have consistently written openly of its dual meaning, representing both the science of Geometry—by which the power and wisdom of the Creator are demonstrated—and the Divine Being Himself 1. The secret aspect of the symbol relates strictly to the manner and object of acquiring that instruction, not to the meaning of the letter 1. Mackey nevertheless regrets its adoption into the system, arguing that because it relies on an English initial, it lacks the universality and antiquity required of genuine Masonic symbolism 1.

The supplied sources do not contain William Preston's specific text or commentary on the letter G.

Frederick Dalcho of South Carolina provided an early American account of the symbol in 1801, explaining that the letter G ornamenting the lodge represents both the Grand Architect of the Universe and the science of Geometry 1. In Dalcho's view, the adoption of the letter expressed respect for scientific inventions that demonstrate the power, wisdom, and beneficence of the Creator 1.

Because G is the initial letter for both "God" and "Geometry" in English, its symbolic function is directly tied to the English language 1. Mackey observes that the letter developed as an English substitution for the Hebrew Cabalistic symbol yod, the initial for Jehovah, serving to supply modern English-speaking lodges with an equivalent symbol for the Deity 1. While the symbol spread across European jurisdictions, Mackey notes that it functions intelligibly as an initial primarily in English and German 1.

The supplied library passages record Dalcho's 1801 South Carolina address as an early American witness to this dual interpretation, but do not trace a separate, distinct line of ritual development unique to American grand lodges beyond its standard English-language usage.