24 The Collection of Astronomic-Geodetic Instruments approved and the Repsold Company in Hamburg had been commissioned for its manufacture, the costs in 1861 amounted to the impressive sum of 1,000 Reichstaler (SächsStA 15096 and 15098). Despite the high purchase price, the Directorate of the Polytechnical School was authorized by the Ministry of the Interior on September 10, 1861, to acquire this large instrument. Nagel was one of three Saxon commissioners for the large-scale arc measurement campaign, alongside professors Julius Weisbach (Freiberg) and Carl Christian Bruhns (Leipzig). Their task was to create for the Kingdom of Saxony a trigonometric network of the first order, consisting of a total of 36 measuring points (within the Central European Arc Measurement). This network was further consolidated by means of an additional 122 measuring points of second order. Nagel was responsible for the trigonometric survey and for placing survey markers at the measuring points. Quite a few of “Nagel’s pillars”, created under his direction, still exist today and are monuments to Saxony’s surveying history. These pillars were used to position the instruments during the measuring process. Nagel’s survey pillars on the Borsberg, Lilienstein, Gohlig and Wilisch mountains are representative examples in the area around Dresden. In 1875, in the midst of Nagel’s intensive work on the land survey, the Polytechnic − as it was then called − moved into the new building on what was at that time Bismarckplatz, roughly on the site of today’s University of Applied Sciences. The new premises did justice to the increased number of students while also providing improved and more up-to-date accommodation for the Geodetic Institute. The rooms for the assistants and the storage rooms for the geodetic collections were situated in the west section of the building on the second floor (facing today’s Fritz-Löffler-Straße), with the geodesy lecture hall and, next to it, Professor Nagel’s office occupying the northwestern corner of the building. It was also possible to include observation pillars for geodetic measurement exercises on the roof of the southern wing of the building. In total, there were seven pillars on the southern roof area, the middle one of which was equipped with a small rotatable dome. This was where the students’ geodetic and astronomical measurement exercises took place. For almost four decades, the polytechnic building near the main railway station, which was built at a later date, became the seat of the Geodetic Institute. Even if the new building could not entirely fulfill all the By decree of the Royal High Minister of the Interior of 10th September, 1861, the most respectfully signed Directorate was authorized to order a large theodolite, universal instrument, to carry out major trigonometric measurements, with the remark that the total cost should be indicated when the time comes. The instrument mentioned has been commissioned by Prof. Nagel from the famous A. u. G. Repsold Company in Hamburg and has arrived here in good condition. From a letter by Julius Ambrosius Hülsse, Director of the Polytechnical School, to the Ministry of the Interior (SächsStA 15100, p. 34). On the platform of the roof of the rear transversal building, a number of strong pedestals for geodetic purposes have been built, and in the middle of the platform (above one of the pedestals) a small astronomical observatory with a rotating housing. Festschrift 1875 “Lohrmann observatory” in the tower of the Beyer Building View of the exhibition, today presenting a cross-section of the most important exhibits of the Collection. As part of a guided tour, visitors can also view the large refracting telescope in the dome.
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