Small 4to. 11 + (1)pp, 1 litho plate. Orig. printed wrappers, preserved in outer protective opaque wrappers. In 1881 Eiffel entered a competition to design a moveable cupola to house the 16m equatorial telescope of the Paris Observatory. He came up with a brilliant alternative to the wheeled mechanism, often difficult to operate, usually used to rotate such cupolas. Specifying steel at this rather early date, he envisaged a latticed dome of 20m diameter from which was suspended a latticed framework comprising the ground floor and observation stair. The whole structure, moving as a single unit, was supported by an annular float in a tank of magnesium chloride at the perimeter of the dome. He patented the system and in this rare item he gives a clear account of it, discussing the structural details, the design of the float and tank, the advantages of magnesium chloride etc. Although the Paris committee turned it down Eiffel was eventually to build such a cupola at the Nice Observatory.
GBP 350.00
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