6.  A piece of brass rod was clamped in the chuck of a lathe, and a depression made in the end slightly eccentric, by means of a center punch.  If the end of the pin is inserted in this depression,

[Illustration:  The Lathe Experiment]

while the hand holding the other end of the stick is kept as nearly as possible in the axis of the lathe, rotation of the lathe will produce rotation of the revolving piece.  Speeds between 700 and 1,100 r. p. m. gave the best results.

7.  A tiny mirror was attached to the end of the pin, and the hand held in the sunlight so that a spot of sunlight was reflected upon the wall.  The notches were then rubbed in the usual way.  The spot of light upon the wall moved in a way which disclosed two components of motion, one circular and one due to the irregular movements of the hand holding the stick.  Usually the orbit was too irregular to show a continuous and closed circular path, but at times the circular motion became very pronounced.  It was observed and the direction of rotation correctly stated by a man who was unaware of the source of the motion.  The production of the circular motion can be explained in this way: 

When the rubbing nail comes to a notch the release of pressure sends the stick upward; this upward motion against the oblique pressure upon the (say) right hand side gives also a lateral component of motion towards the left.  As the nail strikes the opposite side of the notch the stick is knocked down again, this motion relieves somewhat the oblique pressure from the right hand side, and, the reaction from the holding (left) hand moves the stick to the right slightly, so that it is back in the old position for the next upward motion.  Thus a circular or elliptic motion is repeated for each notch, and the direction of this motion is the same whether the nail be rubbed forward or back.  For oblique side pressure from the right (notches assumed upward), the motion of the stick and hence of the revolving piece will be counter-clockwise; if the pressure is from the left, it will be clockwise.

That the motion of the revolving piece is due to a swinging action, and not to friction of the pin in the hole, is proved by experiments 3 and 4.  —­Contributed by M. G. Lloyd, Ph.D., Washington, D. C.

** Home-Made Lantern [163]

[Illustration:  Tin Can Lantern]

The accompanying picture shows a lantern which can be made almost anywhere for immediate use.  All that is needed is an empty tomato or coffee can, a piece of wire and a candle.  Make a hole a little smaller than the diameter of a candle and about one-third of the way from the closed end of the can, as shown.  A wire is tied around the can, forming a handle for carrying.  This kind of lantern can be carried against almost any wind and the light will not be blown out.  —­Contributed by G. A. Sloan, Duluth, Minn.

** A Study of Splashes [164]

When a rough, or greasy, or dusty sphere falls into a liquid, the liquid is