Dept. Bull. 1136, U. S. Dept. of Agriculture PLATE 12 
AUTOMAT, 
RATURE-HE 
ROEDER -CONTROLITY 
grt 7. FEI Maps re 
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AN AIR-OPERATED EXTENSION-TUBE RECORDER CONTROLLER WITH THE 
EXTENSION TUBES IN SINGLE ARMOR 
The functions of this instrument are the same as those of the instruments illustrated in Plates 10 
and 11. Its general appearance is somewhat different, however, because the two pointers by means 
of which it is set are on the right side of the chart, whereas the pens are on the left side. When 
double-pen recorders and recorder controllers are to be used for wet and dry bulb record and control, 
it is usual to inclose the two extension tubes in a single armor, as shown here. When this is done, 
it is obviously impossible to separate the bulbs more than a foot or so, and therefore they can not 
be used independently of each other. ‘This restriction is, in general, of little importance. All of the 
instruments illustrated can be furnished in either style. 
