Popular Science Monthly 



position so as to drain into a sink, wash- 

 basin, bath-tub, laundry-tray or barrel. 

 The hose is connected with a cold water 

 faucet, the trough almost filled and the 

 inlet and outlet regulated to maintain a 

 constant depth of water in the trough. 

 The film, with a film clip attached to each 

 end, is laid in the running water, emulsion 

 side up, or, better still, stood on edge where 

 possible. Film pack negatives may be 

 pinned on a stick the exact length of the 

 trough and placed in the running water. 



Safety Guard Placed on an 

 Emery-Wheel Dresser 



IN the crusade for "safety first" attach- 

 ments on machine tools, one that is 

 likely to be overlooked is the emery-wheel 

 dresser. This, however, has been taken 

 care of in a very efficient manner in one 

 shop as illustrated. A piece of 1/16-in. 

 boiler plate about 2 in. wider than the 



fa j 



Metal guard attached to the handle to 

 prevent flying particles from striking the eye 



cutting wheels of the dresser was bent 

 and fastened with two 3/16-in. screws about 

 % in. long on the handle of the dresser for 

 a guard. — Joseph K. Long. 



A Nest- Box Trap for Catching 

 the English Sparrow 



SPARROW traps may be classified, 

 according to the U. S. Department of 

 Agriculture, as nest-traps and bait-traps. 

 Inasmuch as sparrows usually feed in 

 flocks, but approach nest-boxes singly or 

 in pairs, the annual catch of a bait-trap 

 will exceed that of a nest-box trap many 

 times; but during the breeding season the 

 nest-box traps are decidedly useful. 



A nest-box trap, as the name implies, 

 looks like an ordinary nest-box. The 

 weight of a bird entering such a trap puts 

 into operation a mechanism which catches 

 the bird and sets the trap for another. 

 There are a number of devices to accomplish 

 this. In designing a nest-box trap one 



139 



should bear in mind that English sparrows, 

 like other birds, dislike drafty quarters, 

 and that a mechanism delicate enough to 

 be operated by a sparrow's weight is likely 

 to get out of order unless the parts are few 



A trap-nest for catching the English spar- 

 row in a bag hung from beneath the box 



and perfectly protected from the weather. 



Probably the simplest nest-box trap yet 

 designed is the one illustrated. The essen- 

 tial parts of the trap are: a box, a tipping 

 chamber within the box, a down-spout 

 below it and a bag at the lower end of the 

 down-spout. The dimensions of the several 

 parts are given in the illustration. The 

 tipping chamber is made of tin, the down- 

 spout of wood or tin, the box of wood. 

 The roof board is cleated across the ends, 

 and also lengthwise between the cross 

 cleats, for the attachment of the sides, as 

 shown in the side elevation. 



The close weave of a 2-bushel bag makes 

 it suitable for the lower end of the down- 

 spout. One of coarser fabric would allow 

 a draft through the spout and thus detract 

 from the efficiency of the trap. In building 

 this trap the front wall is the last piece to 

 put in place. It is fastened there with 

 screws so that the trap can be easily over- 

 hauled. It is a good plan to fasten with 

 shellac a few feathers or bits of hay to the 

 floor of the tipping chamber near the rear 

 end to excite the interest of the sparrows. 



Look Over Stored Tires Before 

 Applying Them to Rims 



BEFORE using tires laid aside examine 

 them carefully for cuts on the outside, 

 remove tacks and small nails, reinforce any 

 breaks in the fabric inside and lubricate the 

 fabric and inner tube with powdered mica. 

 Apply a thin solution of graphite, shellac 

 and alcohol according to instructions. 



