Object Description
For sale, a mid-Eighteenth Century, Gregorian reflecting telescope in original oak case by Benjamin Martin of Fleet Street, London.
This small sized example is comprised of a 14” main barrel with a diameter of two and a three quarter inches, and has a 3” screw-in eyetube beautifully engraved to B. Martin, Fleet Street London
Focus is achieved by means of a threaded brass rod with hand adjustment screw on the side of the instrument, which connects to an internal ratchet at the barrel end operating a small concave ellipsoid mirror back and forth. Light travels into the telescope and is reflected onto this mirror by means of a concave paraboloid mirror positioned at the eyepiece end of the barrel and is subsequently reflected back through a hole at the centre of the paraboloid mirror into the eyepiece.
The telescope body is mounted upon a brass tripod with medallion decorated retracting legs and padded feet. The tripod legs may also be removed to reveal a screw mount enabling the user to attach the tripod onto a piece of wood whilst operating in the field. The hole situated at the base of the stem is present to allow manual leverage if required for fixing. The altazimuth head of the tripod is mounted on a decorative scrolled platform and has a telescope rest with slots to accept the screw mounts attached to the barrel. (Please note that there is a minor historic repair to one of the slots which can be seen in the images provided which does not affect in any way.)
The telescope is also completed with its original brass screw-in end cap and retains its original oak fitted case with working lock and key. It also has its two original removable slips which would be slotted over the telescope when packed to reduce movement within the case during transit.
Accompanying the case is an original pen and ink note relating to an owner’s favourable impressions of the telescope and amongst other expectations of its use, considers whether it would be powerful enough to view Halley’s comet. Given that Halley first predicted the comet’s return in 1757 it is likely that this letter dates to the comet’s subsequent return in 1835 owing to the certainty of its transit by the writer. It remains testament to Martin’s workmanship that an instrument manufactured around the time of the comet’s previous appearance continued to be considered in such high regard.
A remarkable survivor of a size seldom seen. The telescope continues to perform extremely well, providing very sharp focus at distance. Evidence of Martin’s reflecting telescopes remain within existing catalogues, and they were sold in varying barrel lengths ranging from four foot down to six inches with or without rackwork.
Benjamin Martin was born in 1705 in a village called Worplesdon, near Guildford in Surrrey. Martin did not follow the path of apprenticeship like most respected instrument makers of the period, his father’s prosperous background allowed him to become a merchant by the age of 24 but he largely worked in Chichester as a schoolmaster during the 1730’s up until his departure in 1742. To give a flavour of this enterprising man, he had by this time published eight books, invented a new form of microscope which he described in his “The Description and Use of a New Invented Pocket Reflecting Microscope” and lectured on philosophy.
Martin lectured extensively across Southern England during the 1740’s and was responsible for numerous educational publications on science, mathematics and English grammar but in 1750’s, he established premises in Fleet Street, London, setting himself up as a scientific instrument maker whereafter his advertisements are recorded in London newspapers of the period.
His inventory grew throughout the 1760’s to include optics, globes, electrostatic machines and all types of philosophical instruments. His enthusiasm unbounded, he also tackled horology and planetariums in the early 1770’s while also producing his famous steelyard coin balance. Business continued to flourish until 1782 but this stellar career ended abruptly with Benjamin Martin taking his own life owing to an impending bankruptcy. There is nothing recorded to suggest that the business was in turmoil, but it is likely that his old age and increasing reliance on others was largely to blame.
An interesting, rare and early example of this highly regarded London instrument maker’s work, circa 1755.