af ield ▁o vers aw ▁the ▁construction ▁of ▁the ▁old ▁cad et ▁library ▁and ▁observ atory , ▁which ▁stood ▁at ▁the ▁intersection ▁of ▁C ull um ▁Road ▁and ▁Jefferson ▁Place ▁near ▁present - day ▁C ull um ▁Hall ▁and ▁the ▁second ▁cad et ▁library . ▁ ▁That ▁library ▁stood ▁on ▁the ▁southern ▁edge ▁of ▁the ▁P lain ▁for ▁ 1 1 9 ▁years ▁before ▁it ▁was ▁demol ished ▁in ▁ 1 9 6 0 . ▁ ▁That ▁library ▁was ▁built ▁in ▁the ▁style ▁known ▁as ▁T ud or ▁Goth ic ▁and ▁helped ▁set ▁the ▁tone ▁of ▁future ▁buildings ▁on ▁the ▁edge ▁of ▁the ▁plain . ▁ ▁The ▁offices ▁of ▁the ▁Super int endent , ▁Ad j ut ant , ▁Qu arter master , ▁& ▁Tre as urer ▁were ▁in ▁the ▁library ▁until ▁the ▁new ▁Head quarters ▁was ▁built ▁in ▁ 1 8 7 0 . ▁The ▁old ▁library ' s ▁observ atory ▁had ▁to ▁be ▁moved ▁up ▁the ▁hill ▁near ▁L usk ▁Res er voir ▁when ▁a ▁train ▁tunnel ▁was ▁constructed ▁under ▁the ▁P lain ▁in ▁ 1 8 8 0 . ▁ ▁The ▁observ atory ▁stood ▁at ▁the ▁top ▁of ▁the ▁hill ▁above ▁the ▁cad et ▁chap el ▁until ▁it ▁was ▁closed ▁and ▁demol ished ▁in ▁the ▁ 1 9 5 0 s . ▁ ▁In ▁ 1 8 5 1 , ▁Del af ield ▁o vers aw ▁a ▁major ▁over ha ul ▁in ▁the ▁bar ra cks ▁conditions ▁with ▁the ▁construction ▁of ▁more ▁modern ▁bar ra cks , ▁built ▁in ▁the