The final lecture in the Jefferson Laboratory course was givne last night by Dr. Whiting on the subject "Matter in Motion." Matter sometimes offers but little resistance to an impulsive force. The touch of a feather, for instance, will set in motion a carefully balanced ball weighing 20 lbs., but only when the force is slowly applied. When a force is exerted suddenly, considerable resistance is offered even by as mobile a body as air. Birds are enabled to fly only by the resistance of the air during the downward stroke of the wings. During the upward stroke, less resistance is offered, owing to the fact that the wing is convex on the upper side, and is at the same time contracted in area, thus moving with less velocity. In fact instantaneous photographs show that it takes twice the time to complete the upstroke that is needed for the downstroke. Unless matter offered resistance, no force could be brought to bear, and force must equal resistance. In a tug-of-war the tension on the rope is equal, and the question is, not who can pull the hardest on the rope, but who can push most vigorously on the cleats. The same results are produced by a great pressure for a short time and by a small pressure for a long time. This is the principle which enables dynamite bombs to be fired. If shot from a cannon the sudden shock explodes the bomb immediately, and the connon is destroyed. But by the use of compressed air in a long tube, thus imparting the velocity gradually, a 1000-pound bomb can be fired two miles without danger to the cannoneer, but with most disastrous effects on the object aimed at. The common notion that force is needed to maintain motion is erroneous; force is only needed to overcome resistance. Without opposition motion would continue forever after being once started. The planets continue to move only because no resistance is offered, otherwise they would have become stationary long ago. In connection with the effect of gravity on matter in motion, Dr. Whiting gave some most valuable advice to novices in bicycle riding. "The easiest way to steer a bicycle is to try to tip it over." Dr. Whiting treated his apparently dry subject in a most entertaining manner, and by means of well-chosen illustrations, both verbal and material, succeeded in giving a lecture that was as amusing as it was instructive.