A barometer that will indicate weather changes with reasonable accuracy may be made of two bottles. A milk bottle nearly filled with water is used as the container and a smaller bottle fitting snugly into the top is inverted in the mouth of the milk bottle. The mouth of the inverted bottle should extend about an inch below the surface of the water. Weather changes will cause the water to rise and fall in the neck of the inverted bottle.
Removable Posts for Tennis Court
The Post may be Removed for Mowing the Court or When Not in Use
It is sometimes desirable to have tennis-court posts arranged to be easily removed from the lawn or the court when the grass is being mowed, or during the winter. The method of fixing the posts in the ground, as shown in the sketch, makes it convenient to remove the posts and still gives the necessary stability. A square wooden box, tarred to resist the moisture, is placed in the ground, and the post is fitted into it. The upper end of the box is level with the surface, and when the post is removed a wooden block is fitted into the opening. Removal of the posts permits the mowing of the grass close to them and leaves the place free from obstructions when the court is not in use.—Edward R. Smith, Walla Walla, Wash.
Lightning Switch for Wireless Aerials
Amateur wireless operators often cannot afford to buy a lightning switch such as is required to ground the aerial when not in use. The sketch shows such a device, which was made of a marble slab fitted with copper strips cut from discarded half-tone plates. The base was smoothed and polished to the size indicated, 4 in. wide and 9 in. long. The upper edges were beveled off, and holes were drilled near the ends through which bolts were passed to fasten the small brackets supporting the crossbar.
Discarded Copper Half-Tone Plates and a Piece of Marble were Used in Making This Lightning Switch for the Wireless Aerials
The copper pieces were made as follows: The plates of ¹⁄₁₆-in. copper were cut into strips, 1¹⁄₄ in. wide. Two were made 8 in. long; four, 3 in. long, and four, ⁷⁄₈ in. long. The 8-in. strips were fastened together with small bolts and a hole was drilled through one end of the joined pieces to fit the bolt which forms the pivot for the switch. The 3-in. strips were bent to form a ³⁄₄-in. angle, through which holes were bored for fastening to the base. The ⁷⁄₈-in. strips were clamped between the brackets at their lower ends to provide a slot for the crossbar. The bolts, by which the brackets were clamped together, were provided with binding nuts to which the wires were connected. A handle might be fixed to the crossbar, but this is not essential.