292 PLANTS 



year, then the number of rings indicates the age of the 

 tree (Fig. 239). Some of the "big trees" of California 

 are estimated to be between 2,500 and 3,000 years old. 

 They are often 35 feet in diameter and over 300 feet high. 



Sawing of Wood. Logs of "soft" wood, such as pine, spruce, and 

 hemlock, are often floated down streams to the sawmills. Fig. 240 

 shows a log "boom," or enclosure, in which logs are kept until they are 



FIG. 239. Felling a Great Tree. Courtesy of the Field Museum. 



sawed. The log is hauled out of the water, and into the mill, by means 

 of a moving, "endless" chain. Here it is gripped by steel "dogs," 

 which hold it firmly to the log carriage. The carriage is then run up 

 to the saw. The saw first cuts off the rounded sides of the log, as 

 "slabs." In ordinary sawing, three sides are thus "squared"; then 

 the squared log is cut into boards by cuts made parallel to one another 

 This is slash-sawing. 



Radial, or rift, sawing is a cutting along lines from the outside of 

 the log toward the center. The cuts are thus made through the pith 

 rays (Fig. 240a). In slash sawing, the central board is the only one 



