Sir David Brewster Patent Telescope for Measuring Distances & Angles by William Harris & Co London

Sir David Brewster Patent Telescope for Measuring Distances & Angles by William Harris & Co London


Sir David Brewster Patent Telescope for Measuring Distances & Angles by William Harris & Co London


33 x 5 x 5




For sale an important George III period, museum quality hand held patent telescope for measuring angles and distances invented by the famous Scottish scientist Sir David Brewster and patented in partnership with the scientific instrument maker William Harris in May 1811.

This unassuming but superbly executed three draw non-achromatic telescope is typical in style for the period measuring 87cms at its full extent with its original sunshade (82.5 without) and 33cms fully retracted (28.5 without sunshade). It has a two inch objective lens and a deep reddish mahogany barrel. It is engraved on the first draw to, “W. Harris & Co. 50 Holborn, London” and is further engraved with “Patent Telescope for Measuring Angles & Distances, No 57”.

The patent gives some sense of its individuality but the telescope distinguishes itself from all others of the period by virtue of an engraved scale to the second and third barrels with further engraved writing stating the following on each side of the scale, “scale of minutes divided object glass” and “scale of minutes single object glass”. The reference to single and divided object glass can be understood by taking the telescope apart where you will notice that the second draw tube unusually contains a second, one and a quarter inch object glass. This second object glass is considered divided from its partner when the telescope becomes extended and thus the meaning of the scale is apparent. When viewing through the eyepiece, you will also notice the inclusion of, “two delicate steel points projecting into the field of view and a pair of parallel fibres, all of which are firmly fixed in their respective positions”.

The final quote in reference to the eyepiece comes from Brewster’s first ever scientific publication in 1813, written two years after the patent was granted, “A Treatise on New Philosophical Instruments for Various Purposes in the Art and Sciences with Experiments on Light and Colours”. In it, he describes a number of instruments which were created and based upon the principals in his book. This extraordinarily rare instrument is one such example and is explained in some detail in Book III, Chapter One.

To copy the entire text in detail would be too extensive to include in this explanation but the main principles are included below:  

“The micrometrical telescope will be found of very great utility to travellers, and to officers of the army and navy, who require an instrument that is portable, and not easily injured, while it can be employed with facility, and without the trouble of tedious calculations.

The micrometrical telescope is represented in its most general form in Plate VIII Fig. 1 (see image included), where AB, BC, CD, DE are the tubes of which it is composed. The principle object glass is placed at A; the second or moveable object glass is situated a little to the left of C, at the end of tube DC; and the eyepiece is contained in the tube DE. When the tubes BC, CD are into the outer tube AB, the moveable object glass at A; and in this situation distinct vision may be procured by pulling out the eyepiece DE. The magnifying power of the instrument is now at a minimum. By pulling out the tube CD, the moveable object glass near C is separated from the principal object glass, distinct vision may again be procured by pushing in the eye-tube DE, and the magnifying power of the telescope will be greater than before. In like manner, by pulling out the tube CB, and producing distinct vision by a new adjustment of the eyepiece, the distance of the two object glasses, and likewise the magnifying power of the instrument will increase till the place of the moveable lens coincides with the principal focus of the object glass, when the magnifying power of the telescope will be at a maximum”.

The above explains the principles of achieving the maximum and minimum focal lengths from the telescope and Brewster continues to explain the methods for constructing the scale of the instrument.

“Having thus pointed out the method of constructing the scale of the telescope, we shall now proceed to shew its application to the measurement of distances. Let D, E Plate VIII. Fig. 3 (see image) be two prominent points in the object whose distance is to be measured, and so chosen that at the station B the pair of points may be made to comprehend the space DE without separating the two objects more than four or five inches.

The telescope being directed to the object, and the tubes BC, CD being pushed into the tube AB, and distinct vision being procured by the adjustment of the eyetube DE, the two steel points should either exactly coincide with the two points D, E Fig. 3 in the object whose distance is to be measured, or should occupy a greater space. If the steel points comprehend a greater interval than that which lies between points D, E of the object, which is most likely to be the case, separate the object glasses by pulling out the first divided tube CD (Fig 1) and produce distinct vision by the eyepiece DE till the steel points exactly coincide with the points DE (Fig 8) or comprehend the object DE, the extremity C of the drawer CD (Fig 1) will then mark out upon the scale the value of the angle DBE”.

Brewster explains that the action is to be repeated at a point further away in order to ascertain a further measurement of the same subject at a lower acute angle. A mathematical equation incorporating the length of the base and the two measurement will therefore provide a calculation of distance. It is perhaps useful to the reader that Brewster goes on to provide a series of pre-prepared scales for quick reference in the field.

The detail continues for numerous more pages but the above gives some consideration of the ingenuity of this instrument and Brewster himself is not shy to point out the possibilities for its use.

“There is one application of the micrometrical telescope to the mensuration of distances, which may, on many occasions be of considerable service to the military engineer”.

It was perhaps an unfortunate case of bad timing that the Napoleonic wars were drawing near to conclusion so this fascinating but slightly complex instrument was perhaps not put to greater use.

Brewster himself needs little introduction. He is perhaps most famous for his later invention of the kaleidoscope but he was born in Jedburgh, Scotland in 1781. Having already constructed a home-made telescope by the age of ten, he was to attend the University of Edinburgh two years later and achieved an MA by the age of nineteen in 1800.

Initially following a career in the church, Brewster also began writing on scientific subjects, mainly the science of optics in 1799 and was a regular contributor to the Edinburgh Magazine for which he also acted as editor and also became the editor of the Edinburgh Encyclopaedia which consumed a significant amount of his time between the years 1808 to 1830.

At the turn of the nineteenth century, Brewster was already active in his own experiments on the subject of optics and had a working relationship with Miller & Adie (later Adie & Son) of Edinburgh and William Cary of London. His relationship with William Harris had already been established by 1809 as it is known that Brewster send a new goniometer that Harris had constructed to Alexander Adie for adjustment. In the above mentioned work Brewster relates that,

“On the 3rd of February 1809, I gave direction to Mr Harris to construct for me a goniometer for measuring by reflection the angle which one line forms with another, or the angle formed by two reflecting surfaces, by observing their relative position to any straight line. I shewed this goniometer to several of my friends in London, during the months of February and March; to Dr Clarke and Mr Woodhouse at Cambridge, on the 22nd of March; and , in the beginning of April, it was exhibited to the mathematical class of this University by Professor Leslie. At this time I got an addition made to the instrument by Mr Adie”.

On the 21st of May 1811, the first of his patents was lodged and it is the patent to which this instrument is associated, namely, “Optical instruments for measuring angles; telescopes and other instruments”. It was lodged at the Patent Office by both Brewster and William Harris (the maker of the instrument) and it is likely that Brewster shared the patent with Harris due to the significant cost and time associated with the process. Brewster was never a man of great financial means according to his biographers and that William Harris was responsible for the administration is clearly stated in the patent itself. “And be it remembered that on the thirteenth day of July, in this year of our Lord 1811, the aforesaid William Harris came before our said Lord the King in his Chancery, and acknowledged the specification aforesaid”.

A more famous example of this kind of business relationship is evidenced through the partnership that was originally formed between the Dollond family and Francis Watkins for the achromatic lens patent. That the Dollond family required this type of support gives one a flavour of the resources required to lodge and fulfil an application.

It is unlikely given the existing rarity of the instruments from this long patent application that many were produced and his early foray into commercialising his inventions was largely overshadowed in 1817 when the invention of the kaleidoscope was revealed.

That Harris seems not to have been involved in either the patent application or advertised as one of the licensed retailers alongside such famous cotemporaries as the Dollonds. Robert Brettell Bate, Matthew Berge and Thomas Jones (amongst others) suggests that their relationship had run its course. Brewster was known to have been a somewhat difficult character so we may assume that the relationship has broken down by then. It is also asserted that Harris by his exclusion from the above list may have been the responsible party for having shown the invention to other scientific manufacturers at the early stages of the instruments conception. Brewster by virtue of its immediate popularity fell prey to numerous imitators and although he held rights under patent law, seemed never (probably for lack of funds) to have tested his rights under law.

With his fame secured though, Brewster went on to become a member of The Royal Society, The Royal Society of Edinburgh and received a knighthood amongst the other various honours that were bestowed upon him throughout his life. He continued to issue or edit numerous publications and took senior positions at Scottish Universities which to some extent alleviated his financial issues but he remained a somewhat nervous and irritable character. His more profitable venture was the invention of the stereoscope in 1849 allowing the viewing of two separate images to combine into a single three-dimensional image. Its success and its launch coincided with the opening of The Great Exhibition where Brewster’s position as a juror must have assisted with it positive acceptance. He went on to support a similar role in the later Paris Exhibition and remained active until his death in 1867 having taken positions with the Berlin University and acted as President of The Royal Society of Edinburgh.

Given the allowances of this description, it is a somewhat mean reflection of Sir David Brewster’s life, his achievements and his prolific nature. His counterpart in the early patent is even less well known but his involvement with Brewster attests to the quality of his manufacture. Harris was known to have had an outlet in Hamburg which is somewhat unusual for the period and adds further weight to his business acumen. It is suggested that he also supplied instruments to the JA Lloyd survey of Panama in 1828 and evidence suggests that Harris made full use of his patent application, often heading his trade cards with the words, “by his majesty’s royal letters patent”.

Examples of this telescope are contained within the collections of the London Science Museum (catalogued but un-pictured) and The National Museum of Scotland where it is pictured and described in the publication, “Martyrs of Science – Sir David Brewster 1781 – 1868” from 1984. There are no other known examples of this early Brewster patented invention.


Ask the Dealer

Item enquiry

To enquire about this item, complete the form bellow to send a message to the Dealer

Enter Email
Confirm Email