Popular Science Mouthlij 



953 



box to a brass cup in the bottom. It is 

 essential tliat tlic arrow swings easily 

 on its pivot. The box should be 3 in. in 

 height and 6 in. scjuare. In the bottom of 

 the bo.\ twoconcenlriccirclesaredrawn. The 

 annular ring between the cireles should 

 measure i in. in width. In this ring, 8 

 curved metal plates are imposed. They 

 serve as commutators. They should be 

 screwed down perfectly flat and the screw- 

 heads filed flush with the metal surface. 

 An air -space of 3/16 in. should exist 

 between the segments. There will be 

 8 segments altogether. To the outside 

 rim of each of these a i-ft. No. 18 annun- 

 ciator, or bell wire is soklered. 



A metal arm, which ])resses down upon 

 the plates with sufficient force to insure 

 an electrical contact, is soldered on the 

 pivot rod a short distance above its base. 

 It is made from spring-brass 3^2 '•!• wide. 

 To counteract its spring-like action, which 

 otherwise would force the rod and the 

 arrow upwards, a ring or flange shoukl be 

 soldered to the rod immediately below the 

 box cover. The tension of the swinging 

 contact should then be adjusted so that, 

 vhen the cover of the box is on, the arrow 

 will swing freely, but at the same time the 

 arm will make firm contact with the 

 segments. To the metal socket into which 

 the base of the rod fits, another i-ft. length 

 of No. 18 annunciator wire should be 

 soldered. The directions of the compass 

 towards which each of the segments point 

 should l)e indicated by tags on the wires 

 which lead from them. This is important. 



The vane wit'i its slider-arm for mak- 

 ing electric connections with the dial 



Otherwise, confusion of an amusing variety 

 will result when the dial is connected and 

 the batteries are in circuit. A westerly 

 wind may be registered as southeast, etc. 

 Holes should be bored in the bottom of the 

 box, to drain off rain water. 



A cable of 9 annunciator wires, properly 



indicated by numbers or letters at the enil 

 of each, should l)e made as follows : Stretch 

 between 2 points, which are as far apart as 

 the distance from the vane to the dial, the 



The wiring diagram showing the electrical 

 connections between the vane and the dial 



9 annunciator wires. Tar them carefully 

 and while the tar is still soft, wrap the 

 "rope" with insulating tape. The cable 

 should be properly connected to the 9 wires 

 from the vane-segments and contact-arm 

 and led to the room where the registering 

 dial is to be mounted. 



This consists of a polished wood box of 

 the sanM* general dimensions as the box 

 on tlrt!^"roof, but with 8 holes each i in. 

 in diameter bored in a circle in its front 

 side. A sheet of ground glass is placed 

 against the holes underneath. The 8 

 directions of the compass are written in 

 black ink on the glass which covers the 

 holes. Under each hole a miniature 

 electric lamp is mounted. The light 

 corresponding to the vane segment which 

 points north is connected to one post of 

 the "north light." The remaining seven 

 segments are connected to their correspond- 

 ing lights on the dial. The remaining 

 8 posts of the lamp are connected together 

 and the wire run to one pole of a gravity-, 

 or blue vitriol, l^attery consisting of 3 fresh 

 cells. The 3 cells are sufficient when the 

 cable from dial to vane is no longer than 

 40 ft. For every additional 10 ft. another 

 cell should be added. If the push button 

 is used, dry cells, not gra\ ily cells, shoulil 

 be employetl. 



The ninth wire of the cable, the one 

 which leads from the pi\-ot of the vane, 

 is connected with the other side of the bat- 

 tery. If the wind is from a northerly direc- 

 tion, the north light of the dial will be 

 lighted ; if in a southerly direction, the south 

 light will show, etc. But if the wind should 

 blow in such a direction that the arm on the 

 pivot rests on two segments simultaneously, 

 two adjacent lamps will light.— G. F. Worts. 



