Charles Piazzi Smyth FRSE FRS FRAS FRSSA (3 January 1819 – 21 February 1900) was a British astronomer who was Astronomer Royal for Scotland from 1846 to 1888; he is known for many innovations in astronomy and, along with his wife Jessica Duncan Piazzi Smyth, his pyramidological and metrological studies of the Great Pyramid of Giza.

[2] His father subsequently settled at Bedford and equipped there an observatory, at which Piazzi Smyth received his first lessons in astronomy.

[2] Shortly after his appointment, the observatory was placed under the control of Her Majesty's Treasury and suffered from a long series of under-funding.

This suggestion fell on deaf ears until in 1856, Smyth petitioned the Admiralty for a grant of £500 to take a telescope to the slopes of Teide in Tenerife (which he spelt Teneriffe) and test whether Newton had been right or not.

This offer was declined as Piazzi Smyth had already designed a tent with a sewn-in groundsheet based on his experience in South Africa.

He made observations of the steadiness and clarity of star images with the 3.6-inch (9 cm) Sheepshanks telescope and found both much better than at Edinburgh.

The dust was evidently confined to individual layers, so he decided to move to Alta Vista at 10,700 ft (3,300 m), on the eastern slope of Teide, the highest point that mules could reach.

Piazzi Smyth was the pioneer of the modern practice of placing telescopes at high altitudes to enjoy the best observing conditions.

[2] He recommended the use of the rain-band for weather forecasting and discovered, in conjunction with Alexander Stewart Herschel, the harmonic relation between the rays emitted by carbon monoxide.

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.

To support this Smyth said that, in measuring the pyramid, he found the number of inches in the perimeter of the base equaled one hundred 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.

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'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 (who adopted the name Jehovah's Witnesses in 1931, though Russell's successor, Joseph F. Rutherford, denounced pyramidology as unscriptural).

The greatest blow to the theory was dealt by the great Egyptogist William Matthew Flinders Petrie, who had initially been a supporter.

Jessie Duncan was a geologist who had studied with Alexander Rose in Edinburgh, and travelled on geological expeditions to Ireland, France, Switzerland and Italy.