294. Nails. Wire nails are best for light work. Get an assortment from ½ in. long up to 1½ in.
295. Screws. It is better to use brass screws around electrical apparatus. For the small work, for binding-posts, etc., use ⅝ No. 5. Another handy size is No. 7, from ¾ to 1¼ in. long. The round-headed screws are best, unless you want to countersink them.
296. Tin. This is really thin sheet-iron, covered with tin. Save up tomato-cans, cracker-boxes, condensed-milk cans, etc. The cracker-boxes are just as good as sheet-tin, as the pieces are large and clean. You can remove the solder from cans by heating them in the kitchen fire. Knock out the bottoms with a poker when the solder gets soft. Clean the tin with sand-paper.
297. Carbons. You can get carbon rods or plates at an electrician's. If you have arc electric lights in your city, you will be able to pick up carbons; these, however, generally have a coating of copper, which must be eaten off with dilute nitric acid. This is a bother. You will find it cheaper to buy the ½ in. rods that are 12 in. long, and uncoated.
298. Shellac. Your wood-work will be much improved by using shellac upon it after you have thoroughly sand-papered it. You can get it, all prepared, at a paint store. Wood-alcohol is used to thin it if it gets too thick. Keep it in a wide-mouth bottle. Paint it on quickly and evenly with a brush, and do not go over it again when it is partly dry. Wait until it is thoroughly hard before putting on a second coat. It should be fairly thin to spread well. Clean your brush in wood-alcohol before putting it away, and keep the shellac bottle tightly corked. A small tin can or a teacup is best to hold the shellac when using it.
HOW TWO BOYS MADE THEIR OWN ELECTRICAL APPARATUS
By THOMAS M. ST. JOHN, Met. E.
| EIGHTH EDITION | Price, postpaid, $1.00 |
This book contains 141 pages, 125 illustrations, and directions for making 152 pieces of apparatus. Size, 5×7½; red cloth.