Transit theodolite

Made by Troughton & Simms in London, England, 1860-1915.

Theodolites have been used to measure horizontal and vertical angles by surveyors since the 1500s. They allow a surveyor to fix a position on the surface of the earth, marking latitude, longitude, and height above sea level, and then map out roads, towns, and plots of land.

Transit theodolites first appeared in the 1840s, the term transit indicates that the telescope can be rotated about the horizontal axis pivoting through 180 degrees and allowing the viewer to easily see both forwards and bac...


Object No.


Physical Description

Transit theodolite with accessories and case, surveyors 6 inch, metal / glass / wood, made by Troughton & Simms, London, England, 1860-1915, used at Sydney Observatory, New South Wales, Australia, 1890-1931

A 6" transit theodolite with attachments including a telescope, three legged metal stand, a spirit level, a lamp and lamp stand, a trough compass, plumb bob, lenses, a small filter, a brass pin and a hook contained in a wooden box with a hinged lid. There is also a tripod for the transit theodolite.

Observatory stock number 248.



The transit theodolite was made by Troughton and Simms in London, England between 1860 and 1915.

In 1782 John Troughton purchased Benjamin Cole's shop in Fleet Street, London enabling him to sell his own signed products. His instrument making business supported several dynasties of Troughton's before becoming Troughton and Simms and later still Cooke Troughton & Simms. This firm was one of the most well respected firms of instrument makers of the 1800s.

While his brother enjoyed some early success the business really expanded once Edward Troughton (1756-1835) took over the business in 1807. Edward and his brother John were both designers and manufacturers of instruments and the quality of their work won them contracts with the leading Government bodies of the time. These included The Royal Society, the Greenwich Royal observatory, the Board of Longitude, the Board of Ordinance and the East India Company.

One of the main factors in the success of the business was the use of a dividing engine which could speed up the labourious process of marking the small divisions of measurement necessary for scientific instruments. This machine was based on that designed by Jesse Ramsden (1735-1800) which had won a prize from the British Board of Longitude in 1775. As a result of this the Board of Longitude was allowed to instruct Ramsden to allow up to ten other instrument makers to copy his machine. One of these was John Troughton and the new machines established both Ramsden's and Troughton's reputations. The dividing engine speeded up both accuracy and production and rather than spending 12 weeks, six days a week and eight hours a day graduating two meridian circles this machine enabled the same job to be completed in around 10 hours.

The workshop produced a broad range of instruments from large telescopes and theodolites through to smaller mathematical instruments. Before 1835 most of the optics appear to have been supplied by Dollond as Edward Troughton was reputed to be colour blind. It is also important to note that from the early years the precision engineering of castings and turnings of their instruments were mainly outsourced to Maudslay Field & Donkin or Ransome's & May.

One of Edward Troughton's apprentices William Simms was taken into partnership in 1826 and after Edward died in 1835 Simms became the manager of the establishment and company became Troughton & Simms. Under Simms the company continued to expand and produced instruments for Britain and her colonies as well as for markets in Europe and America. When William Simms died in 1860 the estate was worth around £80,000. The company was next managed by William Simms (junior) and his cousin James who carried the firm into the industrial age.

The 1860s they moved the company from Fleet Street to two acres of land at Charlton on Woolwich Road and by 1866 the factory employed 61 men and 20 boys. For the 1874 transit Troughton & Simms made only five transits and four portable azimuths but did refurbish some older telescopes loaned for the occasion. Telescopes and transits of the period they were often hybrids with the structure ordered from Grubb's or Troughton & Simms with lenses from Cooke.

However by 1887 the company was able to produce all the parts necessary for their instruments and the company employed nearly 200 people. James Simms died in 1915 and the company was turned into a limited liability company by his two sons William and James. Things however were not so easy for the two sons and in 1922 the business was brought out by their rival T Cooke & Sons becoming Cooke, Troughton & Simms.

Todd, David, P., Stars and Telescopes, Sampson Low, Marston, and Co., 1900
Chaldecott, J., 'Printed Ephemera of Some Nineteenth Century Instrument Makers', in Blondel, C., Parot, F., Turner, A., Williams, M., (eds), Studies in the History of Scientific Instruments, Rogers Turner Books, London, 1989
King, H., C., The History of the Telescope, Dover Publications, New York, 1955
McConnell, A., Instrument Makers to the World; a History of Cooke, Troughton and Simms, William Sessions, York, England, 1992


Troughton & Simms 1860-1915



This transit theodolite was used at Sydney Observatory, Watson Road, Observatory Hill, Sydney, New South Wales, Australia, between 1890 and 1931


Sydney Observatory


Credit Line

Ex Sydney Observatory, 1983

Acquisition Date

13 December 1983

Cite this Object


Transit theodolite 2017, Museum of Applied Arts & Sciences, accessed 25 September 2018, <>


{{cite web |url= |title=Transit theodolite |author=Museum of Applied Arts & Sciences |access-date=25 September 2018 |publisher=Museum of Applied Arts & Sciences, Australia}}


This object record is currently incomplete. Other information may exist in a non-digital form. The Museum continues to update and add new research to collection records.

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