Description
ITEM 9168
‘Troughton & Simms’ 4” Transit Theodolite #9168
This is a relatively rare 4” Transit Theodolite by Troughton and Simms, probably from the late 1800’s. The standard size for general use was 5”. The 4” theodolite was a lighter version for ease of carrying in the field, but with greater accuracy than the 3” ‘Mountain theodolite’.
The ‘size’ of a theodolite is the diameter of the horizontal circle, usually given in inches. Some manufacturers at some periods seemed to take the measurement over the vernier reading scales, other times it was taken over the largest diameter of the limb (the casting containing the horizontal circle).
This instrument is 4” over the verniers and 4½” over the limb. The horizontal and vertical scales are engraved on solid silver and divided to 30” and read by vernier to 1”. It comes in a fitted mahogany case with a trough compass which fits to the underside of the limb, a wall tripod, spanner, and capstan bar. The instrument can be seen mounted on the wall tripod in some of the photos. It has a curved leaf spring to tension the tangent screw; a method not common with Troughton and Simms and which fell out of favour in due course. The telescope focal length is about 8”. With ray-shade and cover to the objective. On the horizontal plate is engraved:
TROUGHTON & SIMMS
LONDON
There is also a very nice tripod available for this instrument, with open-framed square mahogany legs.
The instrument has a well-weathered oxidized brass finish, with original lacquer remaining in the usual areas less subjected to human touch. Of the vernier magnifying lenses, only one is present but all the lens holders are present. The tripod has a bolt and a couple of nuts missing but these do not affect its stability for display purposes.
In summary this is a very neat and highly collectable example of a Victorian transit theodolite, in a rare size, with the patina of age and use expected for a working instrument of this period.
Approximate Dimensions
Instrument: 310mm high overall
Case: 330 x 280 x 148mm high
Tripod: 1.4m long
Approximate Weights
Instrument and case with accessories: 7.5 kg
Tripod: 4.7 kg
Prices
SOLD
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