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The new observatory erected by the Eoyal Government in the neigh-borhood of Potsdam , and whose buildings and equipments are nownearly completed, has for its fundamental purpose the investigation ofthe composition and movements of planetary bodies by means of spec-tral analyses and continued records of the events on their surfaces.
The observatory occupies the so-called Telegraphenberg, formerly astation of the optic telegraph line “ Berlin-Cologne, ” situated south ofthe city of Potsdam, upon the east bank of the river Havel , and about1J kilometers (0.8013 mile) from the railroad depot. On the summit,l m 18 s W. of Berlin , in north latitude 52° 21' 56", 94 meters (318 feet)above the level of the sea and G4 meters (209 feet) above the level of theriver Havel , is located the principal building, supplied with three mov-able cupolas, one of 10 and two of 7 meters (33 and 23 feet) diameter,respectively. Around this are physical, chemical, and photographiclaboratories, workshops provided with a- dynamo-electrical machine,office, janitor’s dwelling, and some other rooms for observations andcollections. Along the gentle northeast slope are three dwelling-housesfor the scientific staff and the messenger; farther down, close to theentrance of the lot and 20 meters (65.6 feet) below the main building,lies the well, accessible for observations down to the level of the riverHavel , the building of the water-works, a shop for the preparation ofoil gas, and a dwelling-house for the machinists.
The observatory is surrounded by a tract of woods which forms adesirable protection against terrestrial radiation and at the same timeserves as a condenser of atmospheric humidity.
This and the adjacent tract of land are the property of the Crown,and thus unobstructed possession for all times is secured for the ob-servatory reservations, now amounting to nearly 17 hectares (42 acres).
The principal instrument of the observatory is a refractor of 0.208 m(11.7 inches) aperture and 5.4 m (17.7 feet) focus, made, together withauxiliary apparatus of spectroscopes and helioscopes, by H. Schroder,of Hamburg; parallactical mounting and micrometers by A. Repsold& Soiine. It is used in plain astro-physical work, but principally forthe observation of fixed stars, spectra of nebula?, and for the study ofplanetary surfaces. Exclusively for solar observations it is proposed touse the second refractor, made by H. Grubb, of Dublin, with a parallac-tic telescope of 0.207 m (8.1 inches) aperture and 3.4 m (11.1 feet) focus,and also a Steiniieil telescope of 0.135 m (5.3 inches) aperture and 2.16“(7 feet) focus, with parallactic mounting by Pistor & Martins. Thiswas formerly used by Professor Sporer, of Anclam, in his solar ob-servations.
Purthermore, for regular photographic work of the sun a specialheliograph is to be employed, of which now only exist the optical parts,made by H. Schroder, an achromatic objective of 0.16“ (6.3 inches)aperture and 4“ (13 feet) focus, together with ocular magnifying glasses,^nd of 0.25“ (9,8 inches) diameter,