24 CLIMATIC CYCLES AND TREE-GROWTH 



immensely the average growth in certain parts of a radial line, but 

 they do not hold to one radial direction and any straight line; cutting 

 them at an angle has inclined rings, which therefore have an added 

 fictitious size. 



Gross-rings only moderately represent climatic change. In an 

 old study it was found that gross-rings in one tree corresponded to 

 similar rings at that date in about half the other trees. They probably 

 occur when for some reason the tree is having rather successful growth, 

 and so they roughly indicate favorable conditions. It would probably 

 improve the curve of the tree's growth if they were reduced to a size 

 somewhat less than half-way between normal and their actual size. 

 The inclination which they so often exhibit can be corrected by meas- 

 uring in a different angle or by a multiplying factor. But either one 

 adds greatly to the labor of handling large quantities of data in tables. 



Spiral gross-rings — A prehistoric section, H-9, from the Aztec 

 ruins has a spiral of enlarged rings, which took about 12 years to make 

 the circuit. It is impossible to tell from the specimen which way the 

 enlargement rotated. The 9-foot Sitka spruce in the American 

 Museum of Natural History shows at some 8 or 10 places about the 

 circuit spiral enlargements with a very slow rotation. 



VERTICAL UNIFORMITY 



Outside tests — The close resemblance between ring records at 

 different heights in the same tree was assured for the yellow pine a 

 score of years ago, but has only recently been tested formally for the 

 sequoia. During the trip of 1925, a windfall in the Springville region 

 offered such a good opportunity for tests of this sort that it seemed 

 worth while to take advantage of it. This tree, whose uniform trunk 

 was about 15 feet in diameter, had been blown down in 1901, according 

 to Mr. Elster, close to the houses at Enterprise, which had been started 

 as a mill-site some three years before. The tree is lying there in excel- 

 lent condition. The Swedish increment borer was used at 9, 15, 

 and 35 feet from the base of the roots and thereafter at each 20 feet, 

 to a distance of 235 feet from the base. At 255 feet small pieces were 

 cut with a saw, in wood which had been a living branch and in a dead 

 part which had been the main stem. This last showed nearly a 

 thousand years in the radial and has not yet been identified, probably 

 on account of the smallness of the rings. Yet 900 years in the living 

 branch were readily dated, and at 20 feet below this point the cross- 

 identification is perfect, though the branches begin nearly a hundred 

 feet lower down. The lowest boring was well within the root system, 

 close to ground-level, and does not identify well after 1700. With 

 this exception, similarity in heartwood record, which extends to about 

 1800, is striking at all heights above the ground. But the sapwood 

 rings show profound differences, due it is thought (p. 101) to irregular 



