This alidade belonged to Columbia University. Its vertical arc, which extends 35 degrees
either way, is graduated to 30 minutes and read by vernier to 2 minutes. The base has a skeletal
structure, making it light and stiff. There is a separate striding level and trough compass. Buff &
Berger were in business together from 1871 to 1898.
Ref: Buff & Berger, Hand-Book and Illustrated Catalogue of the Engineers' and Surveyors'
Instruments (Boston, 1890), p. 104b.