Maker

W. F. S. (according to T. Garver, this stands for William Ford Stanley, see also Cat No. 210)

Model

B236

Serial Number

42229

Dimensions

Telescope Length 230 mm, Height 350 mm

Image

Description

This is a well built Vernier Theodolite with a solid pillar frame and consisting of a vernier reading system for the horizontal and vertical circles instead of an optical micrometer system. The circles are equipped with magnifying glasses attached at opposite ends of each circle for more comfortable vernier reading. The horizontal circle can be read to 10' using the vernier. The instrument consists of: (1) a levelling head which supports the main working parts of the instrument and is capable of being screwed onto a tripod, (2) a lower circular horizontal metal plate with a silver vernier graduation, (3) an upper circular horizontal plate, (4) a vertical circle with vernier graduations and (5) a telescope with the altitude plate bubble attached beside the vertical circle.

The diameter of the vertical circle is 150 mm and the horizontal circle diameter is 140 mm. The horizontal circle is enclosed to prevent damage from dust and grime. 

According to T. Garver, the instrument does not have coated lenses and was originally property of the British military (because of the engraved 'broad arrow'). 

History & comments

The vernier is an auxiliary graduation, placed alongside the main one with the purpose of determining fractions of the graduation unit. The vernier is typically used with theodolites of medium or low accuracy, as well as for simple angle measuring devices.

According to information received from the Science Museum in London, W. F. Stanley & Co Ltd was founded in 1958, producing wooden drawing instruments. Surveying instruments were manufactured since 1866 in London and South Norwood. The company became a limited company in 1900. George Heath and Co was acquired in 1926 and became the Stanley Scientific Instrument Works. Stanley's and Heath & Co were going well in the 1950s and 1960s. The business went into liquidation in 1999.

Conservation

In a fine wooden box

Condition

Slight rust visible on one side of the vertical circle surface

Remarks

• The instrument carries a 'broad arrow' (pointing upwards) under the serial number (B236)
• Thanks to T. Garver for providing additional informnation on the manufacturer and the year of manufacture.
• Thanks to the Information Librarian, Science Museum London, (via T. Garver) for the history of the manufacturer
• Catalogued by T. Ko
• Updated by F. Pall

Dates

Manufactured in the 1930s. Catalogued in 1997 & 2005.