12 



BULLETIN 472, U. S. DEPARTMENT OF AGRICULTURE. 



pencled. The arms are held in place at any given height on the post 

 by means of two metal clamps, as shoAvn in figure 7. 



Each of these arms has a projection extending backward past the 

 rear or guide post, so arranged that when the ring of the lower arm 

 and the hook of the upper arm are swung to a position directly over 



ir IG . 7. — Sectional view of the testing apparatus, showing the position of the shield, the 

 grating, and the plate and how the posts and legs are sunk into the framework. 



the plate in the base these projections are in contact with the guide 

 post. The projection on the lower arm allows the arm with funnel 

 to swing to the left, while the projection on the upper arm allows 

 this arm with its scalebeam to swing to the right. 



The base of the stand rests on three adjustable metal legs which 

 fit into metal sockets sunk into the under side of the base, in the 



