10 



GROWTH IN TREES. 



as a 



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

 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 email lever, the other end of which is connected with the short arm of a recording lever. Th 

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

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

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

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

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

 a contact rod on the opposite side of the tree ie held witfr gentle pressure against the tree and any 

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



