In 2015 this level arrived in the collection. It is a Carl Zeiss Nivellier I, the smaller version of the Nivellier II, designed by Heinrich Wild during his years with Carl Zeiss in Jena, Germany.

Like the Nivellier II, the Nivellier I is a reversion level, which means that the whole telescope and attached vial can rotate around the telescope axis. In this way any misalignment between them will be cancelled out when observing in two faces.

The instrument reflects the following ideas of Heinrich Wild:

• The anallactic telescope of constant length with internal focusing;
• Device for centring the bubble by making apparent coincidence of its two ends as viewed in a prism;
• Cylindrical steel main axis;
• Dust-tight arrangement for foot screws.

Accuracy¹

The 200 millimetres long telescope is considerably shorter than the one of the Nivellier II (see figure 10). It gives an inverted view and has stadia hairs with a 100 times stadia constant. The magnification is 20 times with an aperture of 27 millimetres. Attached to the telescope is the main vial (see figure 2). Being a reversion level this vial can be turned over to the other side, allowing to eliminate any alignment errors between vial and telescope (see figure 4 and figure 5).

The vial of the Nivellier I has an accuracy of 25" per 2mm run. As the vial is of the coincidence type it should be no problem levelling it with an accuracy of 2" or better (0.2mm at 25 metres distance). The Nivellier I is thus of similar dimension as, but less accurate than the first level Wild produced in his own firm, the Wild Heerbrugg N2.

The length of this early 'modern' level is much shorter than period 'old fashioned' levels as the Secrétan Egault level or the J.-B. Tibaut Desimpelaere Lenoir level and already more accurate thanks to the coincidence vial. It was however not until Heinrich Wild started his own company that the dimensions of levelling instruments really started to reduce (see figure 10).

This model of Nivellier I was introduced in 1919,² two years before Heinrich Wild started his own firm Wild Heerbrugg. Based on the serial number the instrument was built in 1928.² Despite its age the instrument came remarkably complete to the collection. Not only the box survived (see figure 5 and figure 6), but so did almost all the tools and accessories in it (see figure 4). The quality of the lacquer is poor, but that seems to be a common problem with these early Carl Zeiss instruments. A previous owner tried to fix this problem by repainting the instrument with black wrinkle paint, covering not only the original black lacquer, but also most of the screws and parts of the footscrews. This was however done without dismantling and cleaning most of the instrument, as a result of which the wrinkle paint started to separate from the instrument.

In addition to that the primary axis got almost completely stuck, while the coincidence vial did not move at all. It took some 10 hours of dismantling, carefully cleaning, lubricating, re-assembling, and adjusting to get the instrument in the current state. The visible scratch and scrape marks originate from the past paint job. The dark grey paint on the telescope and coincidence prisms is not the original (see figure 10), but as no original lacquer was left below it I decided to maintain it, only removing it from those parts where it did not belong (most of the nickelled parts were covered in it).

[1]: Carl Zeiss - Jena, Geodätische Instrumente, Bezeichnung Dieser Druckschift: GEO 20, (Jena, 1921), pp.5-6.

[2]: With thanks to Dr. Wolfgang Wimmer, ms. Dominique Schmied and ms. Marte Schwabe of the Zeiss Archives.