Show force of Compressed Compress edAir Ap the effects of air resistance arl an yell well known in the twelve and one halt wild simplon tunnel where arl an exceptionally high amount of ebern Is required tor for running tho the elect elec tri rit trains the tunnel which to la fifteen feet wide and eighteen feet high u sectional area of two hundred and fifty square feet has haa a venti lab ing current 0 cubic feet of nit nil per second maintained by two largi blast fans at tho the brig end and twe exhaust fans at iselle cselle trains going with this current encounter less re al si stance than in open mir air up to fifteen arill and a halt half miles an hour I but ait oit at al id higher her speeds or in the opposite direction tho the resistance Is much greater lhnn outside coasting by gravito down the seven per one maximum gradient a train even going with the current cannot exceed 0 thirty thirty alve miles per hour on account of the braking by the air |