** Mechanical Trick With Cards [63]

The following mechanical card trick is easy to prepare and simple to perform: 

First, procure a new deck, and divide it into two piles, one containing the red cards and the other the black ones, all cards facing the same way.  Take the red cards, square them up and place in a vise.  Then, with a plane, plane off the upper right hand corner and lower left hand corner, as in Fig. 1, about 1/16 in.

Then take the black cards, square them up, and plane off about 1/16 in. on the upper left hand corner and lower right hand corner, as in Fig. 2.

Next restore all the cards to one pack, taking care to have the first card red, the next black, and so on, every alternate card being the same color.  Bend the pack so as to give some spring to the cards, and by holding one thumb on the upper left-hand corner

[Illustration:  Card Trick]

all the cards will appear red to the audience; place thumb in the center at top of pack and they will appear mixed, red and black; with thumb on upper right-hand corner all cards appear black.  You can display either color called for.  —­Contributed by Ralph Gingrich, Chicago.

** How to Make a Rain Gauge [64]

An accurate rain gauge may be easily constructed from galvanized iron, as shown in the sketch herewith.  The funnel, A, overlaps and rests on the body, B, and discharges into the tube, C, the area of which is one-tenth that of the top of the funnel.  The depth of the water in C is thus ten times the actual rainfall, so that by measuring it with a stick marked off in tenths of an inch, we obtain the result in hundredths of an inch.

A good size to make the rain gauge is as follows:  A, 8 in. diameter; C, 2.53 in. ; length of C, about 20 in.  It should be placed in an exposed location, so that no inaccuracy will occur from wind currents.  To find the fall of snow, pour a known quantity

[Illustration:  Rain Gauge]

of warm water on the snow contained in the funnel and deduct the quantity poured in from the total amount in the tube.  —­Contributed by Thurston Hendrickson, Long Branch, N.J.

** How to Make an Aquarium [64]

In making an aquarium, the first thing to decide on is the size.  It is well not to attempt building a very large one, as the difficulties increase with the size.  A good size is 12 by 12 by 20 in., and this is inexpensive to build.

First buy one length of 3/4 by 1/8-in. angle iron for the frame, F, Fig. 1.  This can be obtained at any steel shop and should cost about 20 cents.  All the horizontal pieces, B, should be beveled 45 degrees at the ends and drilled for 3/16 in. stove bolts.  The beveling may be done by roughing out with a hacksaw and finishing with a file.  After all the pieces are cut and beveled they should be drilled at the ends for the 3/16-in. stove bolts, C. Drill all the horizontal pieces, B, first and then mark the holes on the upright pieces, A, through the holes already drilled, thus making all the holes coincide.  Mark the ends of each piece with a figure or letter, so that when they are assembled, the same ends will come together again.  The upright pieces, A, should be countersunk as shown in the detail, and then the frame is ready to assemble.