﻿Jul. 1136. U. S. Dept. of Agriculture. 



Plate II. 



wa ■ i i 



% 



Fig. I. — Heater Unit for External Blower. 



Fig. 2. — Two-Pen Extension Tube Recording Thermome- 

 ter Sectioned and With Chart Removed. 



The bulbs B are connected to the instrument through the armored tubing T 

 entering at the top of the case. The pens P and pen arms are slightly to the 

 left of the center. 



