Show force of Compressed air the effects of air resistance art an well veil known la in the twelve and ons on half haff zelle simplon tunnel where nit ai exceptionally high amount of energy to Is required for running i the elec electro electra tri trains the tunnel which Is fifteen feet wide and eighteen feet big high with a sectional area of two hundred 1 and fiat eltty y square feet has bus a ing ine current of cubic feet of all per second maintained by two largo larf blast tans fans at the brig end and exhaust fans at iselle cselle trains goina coin with this current encounter less resistance si than in open air up to fifteen and a half miles an hour but at al higher speeds or in the opposite direction the resistance Is much greatel than outside coasting Coast lne by down the seven per one thousand maximum gradient a train even goins going with the current cannot axce exceed ed th furty arty five miles per hour on oil of the tha braking by the tha air |