Nature in Aquatics 97 



A fall after very calm and warm weather, indicates rain with squally 

 weather. 



After reading the barometer indications you can see why we need the 

 other instruments mentioned. 



THE WEATHER VANE 



The Weather Vane to tell us which way the wind is blowing, and the 

 hygrometer to tell us the temperature and how much humidity there is in 

 the air. 



The Weather Vane is the easiest of the instruments to make. It can be 

 just a flag or a piece of cloth hung out in an exposed place where the un- 

 obstructed winds can blow it. Or, to be more exact, we can make our 

 weather vane in a number of ways. We can make sailing ships, or canoe 

 paddles, roosters or windmills. There is no end to the designs for weather 

 vanes and perhaps you can make up a new one. 



In constructing a weather vane of metal or wood, have as much surface 

 behind the pivot as possible; you cannot have too much. You must, how- 

 ever, have as much weight in front of the pivot as the vane weighs behind 

 it. In other words the weather vane must balance on the pivot as far as 

 weight is concerned and be out of balance in areas. Often the telltale on 

 sail boats is made like the illustration which explains this question of areas 

 and weights. 



The pivot must be quite free and made of some noncorrosive material 

 that will not rust fast, brass, bronze, nickel, silver, etc. 



You can also make cross arms indicating the cardinal compass points 

 and attach them just under the weather vane orienting them by a compass 

 or the north star. They will help you to judge the direction of the wind. 



THE HYGROMETER 



The hygrometer consists of two thermometers fastened to a board. One, 

 the dry bulb thermometer, is the ordinary household kind, the other, the wet 

 bulb thermometer, is exactly the same except that the bulb is covered with 



