Having tried many different styles of weather indicators, I have found the kind to be described here to work well, and as the cost of making one is small, it will undoubtedly interest many readers of the magazine. The base consists of a board 20 in. long and 12 in. wide, which should be fitted with cleats on each end to prevent warping. On the back are fastened with round head brass screws, twelve small spools, similar to those used for twist. The screws should be an easy fit for the holes in the spools, and the holes should be smoothed out with around file to get a good bearing. It would also be an advantage to fill the pores in the wood with powdered graphite, which reduces the friction. The arrangement of the spools is shown in Fig. 1.
Obtain an E violin string and make a knot in one end and fasten with a screw at point A, Fig. 1; the string is then carried over the several spools and to the lower end is attached a lead weight, weighing about four ounces. On the front of the board a calendar or ruled record blank may be placed on the top portion. A dial is marked out on heavy card board, as shown in Fig. 2, cutting out a hole in the center to put the shaft or the pointer. The shaft is made of a piece of brass tubing or brass rod of a size to fit one of the twist spools with a drive fit. A hole is bored in the board at the point B Fig. 1, and a pointer is then fitted to the front end.
The pointer is cut out from a piece of thin brass or tin and painted black. The violin string is carried twice around this spool so as to turn the pointer in accordance with the variations in the tension of the string. The calibrating of the dial must be done after the indicator is in operation. The preferable way is to obtain the use of a regular instrument and by taking observations night and morning for several days, several points can be obtained from which intervening points can be worked out. If this method is not possible, it will be necessary to telephone to some weather observatory at stated intervals and get observations in that way. When complete the indicator is mounted in a vertical position in some place about the house, where it will not be reached by the rain or snow and yet be influenced by a change in the humidity.