2 by 6-in. pine, a piece of hardwood for the rudder and a few pieces of boards.  The 2 by 6-in. pieces should be a little longer than one-third the length of the staves, and each piece cut tapering from the widest part, 6 in., down to 2 in., and then fastened to the staves with large wood screws as shown in Fig. 1.  Boards 1 in. thick are nailed on top of the pieces for a seat and to hold the runners together.  The boards should be of such a length as to make the runners about 18 in. apart.

A 2-in. shaft of wood, Fig. 2, is turned down to 1 in. on the ends and put through holes that must be bored in the front ends of the 2 by 6-in. pieces.  A small pin is put through each end of the shaft to keep it in place.  The rudder is a 1-1/2-in. hardwood piece which should be tapered to 1/2 in. at the bottom and shod with a thin piece of iron.  A 1/2-in. hole is bored through the center of the shaft and a lag screw put through and turned in the rudder piece, making it so the rudder will turn right and left and, also, up and down.  Two cleats are nailed to the upper sides of the runners and in the middle lengthways for the person’s heels to rest against.

Any child can guide this bob, as all he has to do is to guide the rudder right and left to go in the direction named.  If he wants to stop, he pulls up on the handle and the heel of the rudder will dig into the snow, causing too much friction for the sled to go any further.  —­Contributed by Wm. Algie, Jr., Little Falls, N. Y.

** How to Make a Small Microscope [408]

Theoretically a simple microscope can be made as powerful as a compound microscope, but in practice the minute size required by the simple lens to give the highest power makes it almost impossible to be used.  However, a lens having a reasonable magnifying power can be made in a few minutes for almost nothing.  Take a piece of glass tubing, heat one place in a hot flame, hold one end and pull on the other and draw the heated place down to a fine string as shown in Fig. 1.  Take about 3 in. of this fine tube and heat one end which will form a glass bead as shown in Fig. 2.  This bead is the lens.  When in this form it can be used only in an artificial light coming from one direction, but if you take a piece of

[Illustration:  Lens Formed by Heat]

cardboard and bore a hole in it a little smaller than the bead on the glass tube which is forced into the hole, Fig 3, you can use this mounted lens in ordinary daylight.  In this case a mirror must be used to reflect the light up through the lens.  It is difficult to see anything at first, as the lens must be held very close to the eye, but in practice you will soon learn to see the object as it appears enlarged.

If you soak a little dried grass or hay in water for a few days and look at a drop of this water, germs in various life forms can be seen.  The water must be put on the lens.  One thing to remember is that the smaller the lens, the greater the magnifying power.  —­Contributed by Daniel Gray, Decatur, Illinois.