▁the ▁top ▁of ▁the ▁sum mit , ▁so ▁he ▁built ▁his ▁own ▁permanent ▁cabin . ▁ ▁J ans sen ▁observ atory ▁ ▁In ▁ 1 8 9 0 , ▁Pierre ▁J ans sen , ▁an ▁astronom er ▁and ▁the ▁director ▁of ▁the ▁Me ud on ▁ast ro phys ical ▁observ atory , ▁considered ▁the ▁construction ▁of ▁an ▁observ atory ▁at ▁the ▁sum mit ▁of ▁Mont ▁Bl anc . ▁Gust ave ▁E iff el ▁agreed ▁to ▁take ▁on ▁the ▁project , ▁provided ▁he ▁could ▁build ▁on ▁a ▁rock ▁foundation , ▁if ▁found ▁at ▁a ▁depth ▁of ▁less ▁than ▁ ▁below ▁the ▁ice . ▁In ▁ 1 8 9 1 , ▁the ▁Swiss ▁survey or ▁Im feld ▁d ug ▁two ▁ ▁horizontal ▁t unn els ▁ 1 2 ▁m ▁below ▁the ▁ice ▁sum mit ▁but ▁found ▁nothing ▁solid . ▁Con sequently , ▁the ▁E iff el ▁project ▁was ▁abandoned . ▁ ▁Despite ▁this , ▁the ▁observ atory ▁was ▁built ▁in ▁ 1 8 9 3 . ▁During ▁the ▁cold ▁wave ▁of ▁January ▁ 1 8 9 3 , ▁a ▁temperature ▁of ▁ ▁was ▁recorded ▁on ▁Mont ▁Bl anc , ▁being ▁the ▁lowest ▁ever ▁recorded ▁there . ▁ ▁Le vers ▁attached ▁to ▁the ▁ice ▁supported ▁the ▁observ atory . ▁This ▁worked ▁to ▁some ▁extent ▁until ▁ 1 9 0 6 , ▁when ▁the ▁building ▁started ▁lean ing ▁heavily . ▁The ▁movement ▁of ▁the ▁le vers ▁corrected ▁the ▁lean ▁slightly , ▁but ▁three ▁years ▁later ▁( two ▁years ▁after ▁J ans sen ' s ▁death ), ▁a