Bul. 1200, U. S. Dept. of Agriculture. PLATE XVIII. 
Fic. 1.—Apparatus used in controlled temperature tests, showing block in position for testing the 
eat resistance of Douglasfir bark. A, heating apparatus: B, rheostat; C,switch; D, potenti- 
ometer; E, presto tank; F, block ofgreen Douglas fir with thermocouples inserted to cambium 
Ting. 
Fig. 2.—Cone of noble fir prepared for insertion into heating apparatus. On bothsidesare shown 
thermocouples for recording the heatapplied. Thereisalsoa thermocouple in the center ofthe 
cone for recording inside temperature. 
