Note 79 — PART XIII. ADHESION AND TRACTION.

The question whether the centre of the axle or the point of contact with the rail is the fulcrum of the lever in this case has been the subject of much animated discussion and contention. As the word fulcrum means “a point about which a lever moves,” it is believed that the dispute is due simply to a difference in the meaning assigned to the word fulcrum. If we regard the fulcrum as the point which is fixed in relation to the locomotive, then it is at the centre of the axle, but if we refer it to the surface of the earth, then it is at the top of the rail.