12 BULLETIN 472, U. S. DEPARTMENT OF AGRICULTURE. 
pended. The arms are held in place at any given height on the post 
by means of two metal clamps. as shown 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 
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Fic. 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 
