12 GROWTH IN TREES. 
tion of the wooden side arms. As the temperature coefficient of such 
wood is about 0.000054, or 3 times as great as that of brass, extensive 
and difficult corrections were necessary. 
The U-shaped floating frame was retained during the earlier stages 
of development of the dendrograph, and this form has some desirable 
features, especially when the record of a slowly growing tree is to be 
obtained for a long period. Such frames have now been used in 
securing records of growth of Pinus radiata No. 1 for two seasons; 
however, the enlargement is at such a rapid seasonal rate that the 
frames must soon be replaced. 
The final form of the floating frame is that of a polygon constructed of 
strips or bars of invar or bario, 15 to 30 cm. in length, 3 to 5 mm. in 
thickness, and 12 to 15 mm. in width. These pieces have slots near 
each end, about 5 to 8 cm. long, through which short bolts are passed. 
When five to eight such strips are joined to form a suitable frame about 
a tree, the nuts on these bolts are tightened and the joined parts are 
held as rigidly as of one piece. One of the members of the floating 
frame carries a block of metal welded to it and bored to receive the 
contact screw which is provided with a set nut. The member of the 
floating frame which is nearest the instrument block carrying the 
recorder is bored to receive the small bolts which carry the lever set 
designed especially for this instrument. 
The essential feature of this lever set is a quartz rod, 3 or 4 mm. in 
diameter, 7 or 8 cm. in length, which slides in holes of the vertical 
arms of the adjustable frame of the set. The outer end of this rod 
is fitted with a slotted cap or guide by which its rounded end is kept 
in place against the short arm of an L-shaped lever. The long arm 
of this lever carries a pen of the type used on thermographs. The 
dropped arms of the frame which carry the sliding quartz rod have 
three pairs of holes, so that the rod placed in the lowermost holes en- 
gages the short arm of the lever near its end, thus causing the least 
amplification of its movement in the record, which is ordinarily about 
10 times. The rod when placed in the middle pair of holes causes the 
pen to move through an are 15 times as great as the motion of the 
rod, and when placed in the uppermost holes the bearing against the 
short arm of the lever is so near the pivot that an amplification of 22 
is made in the record. The actual amplification is of course tested for 
each instrument. The metal parts of the lever set are of monel, since 
this avoids corrosion and the construction (as shown in fig. 2) is such 
that all of the necessary adjustments are made possible by sliding the 
parts of the frame upon each other. : 
The recorder is also of a design perfected for use with this instru- 
meat. A strong clockwork is inclosed in a heavy case. The upwardly 
projecting end of the main arbor of the clock is fitted with a cap over- 
jutting in such manner that, when in place, water coming down as 
