66 CLIMATIC CYCLES AND TREE-GROWTH 



kindly gave the necessary permission. These logs came from the 

 Lukaichukai Mountains east of the Chin-lee Valley, south of the 

 Chuskas and north of Fort Defiance and Gallup. A day on horseback 

 was spent in the wonderful canyons there, De Chelly and Del Muerto. 

 Then we drove southeasterly up onto the Lukaichukai Mountains and 

 obtained borings in several places, ending at the sawmill 13 miles 

 north of Fort Defiance. These borings and the radials from Chin-lee 

 agree with the Flagstaff series. 



We motored southeast to Gallup and then 100 miles northeast 

 to Chaco Canyon, and there a most interesting search was made for 

 living pines, a number being found at distances of 2 to 20 miles east 

 of Pueblo Bonito. These pines, which appear to be a remnant of a 

 great forest on those mesas in past ages, also show the Flagstaff series 

 of rings. From Chaco our return trip carried us to Gallup, Holbrook, 

 and the Petrified Forest, Ream's Canyon, Walpi, Oraibi, Leupp, and 

 Flagstaff, 16 days from leaving it. 



Rio Grande Valley — During a trip to the Rio Grande Valley in 

 April 1927, specimens of tree-growth from the Zuni Forest, south of 

 Grant's, New Mexico, and from the Jemez Mountains, west of Santa 

 Fe, were obtained. Each locality shows a perfectly clear Flagstaff 

 record. 



Navajo Mountain — By courtesy of Mr. H. Richardson, a trip was 

 made in May 1927 to Navajo Mountain, Rainbow Bridge, and Rain- 

 bow Lodge. Specimens of Douglas fir from the south slopes of the 

 mountain show a perfect Flagstaff record. These recent collections 

 therefore leave no further doubt that the whole Pueblo area west of the 

 Rio Grande is homogeneous in its tree-growth and forms part of the 

 large Flagstaff area. 



SOUTHWESTERN CONTOURS 



The large southwestern arid area is bounded on the west by 

 the range of Southern California mountains, including San Antonio, 

 10,080 feet, San Bernardino, 11,600 feet, and San Jacinto, 11,000 

 feet, which, therefore, form a great rampart impeding the westerly 

 winds. East of this range is the Imperial Valley, with the Salton 

 Sea some 200 feet below sea-level. The Charleston Mountains form 

 an isolated island at the southern point of Nevada. East of the 

 Colorado River the land rises to the plateau of northern Arizona, 

 while in the southern part of Arizona the land rises to the east 

 very gradually, with many "island" mountains high enough to have 

 pine trees upon them. The Mogollon Mesa, often called the Rim, 

 is the bold and lofty southern edge of the Colorado plateau. It 

 cuts across the central part of the State, pointing generally a little 

 south of east. South of it are the island mountains; north of 

 it the land descends gently to the Little Colorado River and then 



