COLLECTION OF SECTIONS. 



27 



1900 



Year 



1905 



1910 



THE SECOND FLAGSTAFF GROUP OF SEVEN SECTIONS. 



In 1911 the writer visited Flagstaff again and made a trip into the 

 forest where cutting was going on, in order to procure a few additional 

 samples of the yellow pine which would check the recent part of the 

 tree-record previously obtained and bring it up to date for comparison 

 with rainfall values. The location was about 12 miles southeast of 

 town and from 6 to 12 miles east of the region from which the first 

 Flagstaff group was obtained. Seven cuttings 

 were procured from the edges of stumps, thus 

 bringing away a triangular pyramid of wood, 

 which included the outer 50 to 100 rings. 



Figure 4 shows how well the second group 

 checks the first and indicates that even a small 

 group of trees, no more than 7 in number, is 

 sufficient to give results of considerable accu- 

 racy. Indeed, we may go further and say that 

 a single tree under favorable conditions may 

 give results of very great value. This is evident 

 in figure 5, where the 7 sections from the last 

 Flagstaff group are plotted separately, the most 

 rapid grower at the top, just below the rainfall 

 curve, and the slowest-growing tree at the 

 bottom. All rise alike because the conditions 

 of rainfall in 1900-10 were more favorable than 

 in the preceding decade, but all (especially the 

 curve of section 4) show a more or less close 

 relation to the rainfall at Flagstaff, even though 

 that town was some 12 miles away. The great 

 sinuosity which a quick-growing tree may show 

 is well illustrated in section 4 in the great dif- 

 ferences between successive years. A lack of 

 sinuosity is shown in section 5 at the bottom. 

 This difference supports the conclusion already 

 reached that slow-growing trees are of less value 

 than rapid ones in the determination of climatic 

 cycles. The results of the measures of this group serve as a check 

 on the preceding measures and are shown in the figures just referred to. 

 They are, therefore, not tabulated in this book. 



THE PRESCOTT GROUP. 



Prescott is located in the northerly part of the Bradshaw Mountains, 

 at an elevation of 5,200 feet. The rocky subsoil is largely granite 

 disintegrated at the surface and worn into steep hillsides, deep gorges, 

 and picturesque masses of rounded boulders. The ridges are sharp 

 and rugged, and the general contour is very irregular. There are very 



FIG. 5. Growth of indi- 

 vidual trees compared 

 with precipitation at 

 Flagstaff. 



