578 TRANSACTIONS OF THE 



dependence on each other, lie so clear before the eye, that the 

 least gifted capacity cannot fail quickly to understand them. 



There is but little friction in an oscillating engine, on account 

 of the small number of rubbing parts. It requires less repair 

 than the ordinary engine, because the principal parts are in such 

 a position that if they become defective, the defects are sooner 

 discovered and more easily rectified. The piston rod requires no 

 guiding, as the stuffing box suffices. The oscillating engine 

 solves one of the most difficult problems in the construction of 

 the steam engine, namely : to convert rectilinear into circular 

 motion. A locomotive engine will oscillate far more at high 

 velocity on a straight road, than on one gently curving, and will 

 not oscillate at all if one track is lower than the other. 



The resistance diminishes as the number of cars are increased; 

 as the direct resistance of the air takes place only on the loco- 

 motive of the train, deduct the resistance of it, and you will dis- 

 cover the resistance of the intermediate cars. 



The wind has a velocity of twenty feet per second, and causes 

 on a surface of a square foot, a pressure equal to one pound and 

 a fraction. Thus a locomotive presenting a surface of 22 square 

 feet, would meet a resistance from the atmosphere of about twenty 

 pounds per ton. The direct resistance of the air against the 

 locomotive once deducted, the resistance per ton no longer depends 

 upon the number of cai-s. When the wind blows oblique to the 

 line of road it acts by direct impulse upon the cars, and also im- 

 pels the wheels to come in contact with the edge of the rail, 

 increasing the friction and retarding the train. When the rails 

 are either very wet or exceedingly dry, they present the least fric- 

 tion. When partially dry they collect dust, and offer great 

 resistance. The friction by the rolling of car wheels is undoubt- 

 edly a uniform retarding force, both with respect to weight and 

 velocity. An engine working upon a level undergoes, from its 

 load bearing upon the wheels, a certain degree of resistance, and 

 in going up an inclined plane the load presents not only the same 

 friction of the wheels, but also a surplus of resistance, proceed- 

 ing from the tendency of the train to roll back towards the foot 

 of the plane. The force that draws the train backwards depends 

 on the weight of the train and inclination of the plane. The 

 friction of wheels is as the diameter of the axle directly, and as 

 the diameter of the wheel inversely. 



At a former meeting of the Club I made a few remarks on the 

 subject of friction, relating to car brakes. I will now complete it. 



