** Rolling Uphill Illusion [361]

This interesting as well as entertaining illusion, can be made by anyone having a wood-turning lathe.  A solid, similar to two cones placed base to base, is accurately turned in a lathe, the sides sloping to an angle of 45 deg.  The spindle can be turned out of the solid at the same time as the cone; or, after turning the cone, drive an iron or wood shaft through the center making a tight fit.

The boards for the track are made with a sloping edge on which the cone is to roll.  This slope will depend on the diameter of the cone, which can be any size from 3 to 12 in.  The slope should not be too flat, or the cone will not roll, and it should be such that the

[Illustration:  The Illusion]

one end will be higher than the other by a little less than half the diameter of the cone.  Thus it will be seen that the diameter of the cone determines the length of the slope of the tracks.  A notch should be cut in the tracks, as indicated, for the shaft to drop into at the end of the course.

The lower end of the tracks are closed until the high edge of the cone rests upon the inside edges of the tracks and the high end spread sufficiently to take the full width of the cone and to allow the shaft to fall into the notches.  When the cone and tracks are viewed from the broadside the deception will be more perfect, and will not be discovered until the construction of the model is seen from all sides.  Should it be difficult to make the cone from wood, a good substitute can be made from two funnels.  —­Contributed by I. G. Bayley, Cape May Point, N.J.

** Annealing Chisel Steel [362]

Persons who have occasion to use tool or carbon steel now and then and do not have access to an assorted stock of this material find that the kind most readily obtained at the hardware store is the unannealed steel known as chisel steel.  Machining or filing such steel is exceedingly slow and difficult, besides the destruction of tools; as a matter of fact this steel is intended for chisels, drills, and like tools which require only forging and filing.  If this steel is annealed, it can be worked as easily as the more expensive annealed steel.

Annealing may be done by heating the steel to a cherry red, not any more, and burying it in a box of slaked lime, where it is allowed to remain until all the heat is gone.  If well done, the metal will be comparatively soft and in a condition to machine easily and rapidly.  In lieu of lime, bury in ashes, sand, loam, or any substance not inflammable, but fine enough to closely surround the steel and exclude the air so that the steel cools very slowly.

If possible, keep the steel red hot in the fire several hours, the longer the better.  In certain processes, like that of file manufacturing, the steel blanks are kept hot for 48 hours or more.  Where it is impossible to wait so long as the foregoing method takes, then a cold water anneal may be used with less time.  This method consists of heating the work as slowly and thoroughly as the time will permit, then removing the steel from the fire and allowing it to cool in the air until black and then quenching in water.