▁S éré ▁de ▁R ivi ères . ▁Comp ared ▁with ▁later ▁S éré ▁de ▁R ivi ères ▁system ▁for ts , ▁the ▁fort ' s ▁design ▁is ▁rem in is cent ▁of ▁the ▁bast ioned ▁en clos ures ▁of ▁Va ub an ▁of ▁the ▁ 1 8 th ▁century . ▁ ▁In ▁their ▁developed ▁form , ▁the ▁S éré ▁de ▁R ivi ères ▁for ts ▁of ▁the ▁ 1 8 7 0 s ▁were ▁much ▁simplified ▁in ▁plan , ▁with ▁less ▁over t ▁reference ▁to ▁historic ▁pro tot ypes . ▁ ▁Cas em ates ▁were ▁arranged ▁on ▁two ▁levels . ▁As ▁constructed , ▁a ▁large ▁proportion ▁of ▁the ▁fort ' s ▁art illery ▁was ▁placed ▁on ▁the ▁surface ▁of ▁the ▁fort , ▁exposed ▁to ▁high - angle ▁art illery ▁fire . ▁This ▁was ▁not ▁considered ▁a ▁major ▁dis adv antage ▁in ▁the ▁ 1 8 6 0 s , ▁when ▁most ▁oppos ing ▁art illery ▁was ▁expected ▁to ▁be ▁smooth - bor ed ▁guns ▁firing ▁solid ▁shot ▁or ▁gun pow der - filled ▁shell s ▁on ▁a ▁low ▁traject ory , ▁with ▁the ▁aim ▁of ▁batter ing ▁the ▁walls ▁of ▁the ▁fort ▁so ▁that ▁bre aches ▁could ▁be ▁explo ited ▁by ▁inf antry . ▁During ▁the ▁ 1 8 7 0 s ▁rif led ▁guns ▁came ▁into ▁w ides p read ▁use , ▁making ▁exposed ▁m ason ry ▁walls ▁danger ously ▁vulner able . ▁At ▁the ▁same ▁time , ▁f uses ▁were ▁developed ▁that ▁enabled ▁shell s ▁fired ▁at ▁a ▁high ▁angle ▁from