Antique brass surveying compass for theodolite. France Spain, c.1900

Antique brass surveying compass for theodolite. France-Spain, c.1900

Large format antique surveying compass made of brass and preserved in its original wooden case, conceived as an accessory for a theodolite and for professional orientation and alignment work in the field. This is a technical instrument from the late nineteenth century or early twentieth century, intended for land surveying, engineering and field measurement, not for educational or decorative use.

The compass features a circular solid brass body, protected by a robust perimeter ring and mounted on a brass support arc. This arc allowed correct positioning, fixing and stability during use together with a theodolite or other surveying instruments. The dial has an approximate diameter of 13 cm and retains its original magnetised needle, well centred on its metal axis. The circular scale is graduated in 360 degrees, with clear and precise numbering for reading magnetic bearings.

At the centre of the dial the inscriptions “Ortega á Madrid” and below “Ladois jeune, fab. á Paris” are clearly visible, meaning Ladois the younger, manufacturer in Paris. This double signature is characteristic of scientific instrumentation of the period and reflects a common practice. Instruments manufactured by specialised French workshops and commercialised in Spain by local technical houses, which added their name as distributor.

The set includes a brass angle protractor, conceived to be mounted on the theodolite in order to measure inclination or slope angle during fieldwork. This accessory allowed the inclination of the instrument axis to be determined and complemented angular and orientation measurements. The set is accompanied by several original fixing and fastening pieces, period screws and two brass plumb bobs, used to ensure correct verticality of the instrument during measurements. All elements belong together and fit precisely into the compartments provided inside the case.

The original case is made of solid wood, with a strong structure and interior compartmentalisation made to measure to protect the compass and all its accessories. It retains its original configuration and shows wear consistent with professional use. The general condition of the set is good. The brass shows a natural patina and small surface marks typical of technical use, with no deformations or visible losses. No modern restorations or replaced parts are observed. The set is preserved complete, coherent and authentic.

This piece fits perfectly into a collection of scientific, surveying or historical engineering instruments, representing a period prior to the generalisation of modern optical instrumentation. Due to its specific function as a theodolite accessory, it is an uncommon piece. It stands out for retaining its original case and all accessories. Its brass construction quality and good overall condition make it an excellent opportunity for specialised collectors or technical display.

Measurements: Case 31 × 23.5 × 8 cm, (12.20 × 9.25 × 3.15 in). Compass diameter 13 cm, (5.12 in.)

History of the Ortega á Madrid Surveying Compass for Theodolite

During the nineteenth century and early twentieth century, this type of surveying compass was an essential element in land surveying work, especially as a complement to more complex instruments such as the theodolite. These compasses allowed magnetic bearings to be determined, the main instrument to be oriented and alignments to be checked during surveying operations.

France was one of the main European centres for the manufacture of precision scientific instruments. Specialised Parisian workshops produced compasses, levels and surveying accessories for engineers, surveyors and technical institutions throughout Europe. Among these manufacturers was Ladois the younger, whose name appears on this piece as the maker.

At the same time, Spanish commercial houses acted as distributors of this equipment on the national market. “Ortega á Madrid” is documented as a dealer and distributor of scientific and surveying instruments active in the early twentieth century. Its name appears on various pieces as a sales or representation mark, without necessarily implying direct manufacture.

The presence of both inscriptions reflects a common commercial practice. Instruments manufactured in France and commercialised in Spain by local distributors, facilitating their use in public works, railways, mining and civil engineering projects.

Theodolite compasses such as this one were used in fieldwork, forming part of the technical equipment together with angle protractors and plumb bobs, and allowed the correct orientation, leveling and inclination of the theodolite to be ensured. In the workshop or office, they were used for adjustment, verification and teaching purposes. Today, complete sets with their original case are especially valued for their technical coherence, authenticity and historical significance.