10 



GROWTH IN TREES. 



The second and preferable form of base may be described in a phrase 

 as a belt of wooden blocks hinged together. Seasoned and oiled 

 blocks of redwood (Sequoia sempervirens) , 15 by 7 by 7 cm., were 

 bound together in a belt by pairs of galvanized strips of iron. Small 

 bolts passed through the ends of these strips and through holes near 



FIG. 1. Earlier form of dendrograph with which all records previous to September 1920 were 

 made. This instrument takes a bearing from a prepared area on the bark of the tree by one end 

 of a small lever, the other end of which is connected with the short arm of a recording lever. The 

 improved instrument includes a lever set, in which the bearing on the tree is made by a hori- 

 zontally moving quartz rod, as shown in fig. 2. An encircling belt of wooden blocks serves as a 

 base and support. Flexible wire standards, with a base of thin sheet metal, are clamped in 

 position on the wooden blocks, and screw clamps which slide up and down on the wire standards 

 serve to hold the floating frame in a horizontal position. The entire apparatus is so adjusted that 

 a contact rod on the opposite side of the tree is held with gentle pressure against the tree and any 

 variation in diameter is then expressed by movements in the lever set. 



