98 Nature in Recreation 



a cotton wick extending down into a small bottle of water. The two ther- 

 mometers are mounted on a board and placed upright in a box that has 

 had holes drilled in three sides to allow a free circulation of air and yet not 

 allow too much wind to strike the wet bulb. This would cool the wet bulb 

 too much and give an incorrect reading. The two thermometers will have 

 to be bought, the rest of the instrument can easily be made with a hammer, 

 saw, and brace and bit. In buying thermometers go to some store that has 

 several on display, look them all over to find what the average reading is 

 and purchase two whose readings are as near the average as possible. 



PRY WET \f___ 



BUIB 50L6 



The wet bulb thermometer gives you the temperature at 100% humidity 

 and the dry bulb the temperature at the humidity of the air. By subtracting 

 the wet bulb reading from that of the dry bulb and consulting the following 

 table you can find out what the humidity is. 



