Show Force of Compressed Air The effects of air resistance an art artWell artwell well known In the twelve and one one- half balf nine mue Simplon tunnel where an ac exceptionally high amount of energy is required for tor running the electric trains The tunnel which Is fifteen feet teet wide and eighteen feet teet high with a sectional area of two hundred and fifty square feet teet has a Ing current of ot cubic feet of nil alt nil per second maintained by two large largi blast fans at the Brig end and exhaust fans at Trains going with this current encounter l less ss resistance resistance re reo re- re than In open air up to fifteen and a half halt miles mUes an hour but at al higher speeds or In the opposite direction direction diree tion the resistance Is much greater greatel than titan outside Coasting by gravity down the seven per one thousand maximum gradient a train even going going goIng go- go Ing with tho the current cannot exceed thirty five miles per hour on account of f the braking by the air |