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 arc 15 tunes 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- 

 ment. A strong clockwork is inclosed in a heavy case. The upwardly 

 projecting end of the msin arbor of the clock is fitted with a cap over- 

 jutting in such manner that, when in place, water coming down as 



