Drawing in black ink on tracing paper showing section, ground plan and plan at gallery. [Plans were drawn up by the Clerk of Works in 1879. The building was completed in 1882 but only used until 1899, when the whole of the Observatory’s library was moved to a new home in the east, north and west wings in the basement of the New Physical Building, while the photographic plates together with the spare stock of the Observatory’s numerous publications (that had until then had been stored in a wooden shed) were moved to the upper floor].