GROWTH IN TREES. 13 
rain does not enter the case. A circular table or base is fitted to the 
cap, and a drum made of a section of large brass pipe sits directly on 
this fitting inside its raised rim, so that it may be removed without dis- 
turbance of the clockwork. 
The new feature of importance of this cylinder is the manner in 
which the record paper is attached. The paper is 80 mm. in width and 
| 
| 
Fig. 2.—Improved dendrograph lever set. A, inner end of quartz rod in contact with prepared 
surface on the bark of the tree. The outer end of the quartz rod is fitted with a metal guide which 
engages the short arm of the recording lever at B. The long arm of the recording lever, D, 
carries a pen which makes a tracing on ruled paper on arevolving drum. The horizontal member 
of the frame C, which carries the recording lever, may be toward or away from the tree to adjust 
the pen at any point on the paper record sheet. 
ruled to millimeters. When placed on the drum the ends are thrust. 
through a slot 1 mm. in width and the free ends are creased on the 
inside without further fastening. When the drum with the paper so 
attached is set on its circular base the paper is properly in position 
when its lower edge is in contact with the rim of the base. A covering 
as described below is placed over the recorder, but in any case actual 
rain falling on it would mar only the record and could not damage the 
instrument. 
The floating frame, however, is exposed to all features of the weather 
and to the effects of sunlight which might cause its temperature to 
vary from about 0° C. to 25° C. during the growing season of the trees 
