Dept. Bull. 1136, U. S. Dept. of Agriculture PLATE 11 
DIRECT~SET 
PERATURE —~ HUMIDI 
URNS, 
CON 
AN AIR-OPERATED EXTENSION-TUBE RECORDER CONTROLLER WITH 
A WATER BOX 
This instrument has the same functions as the one illustrated in Plate 10, although it is 
equipped with a wet wick and water box, whereas the other one has a porous sleeve. Either 
style of wet bulb may be had with any of the recorder controllers on the market. The two 
pointers by means of which the instrument is set are shown directly beneath their respective 
pens, which is the normal operating position. 
