TREE RECORDS: GEOGRAPHICAL DISTRIBUTION 65 



grow intercept the westerlies and partake strongly in the variations of 

 the coast. This zone has a secondary rainy season in midsummer, 

 torrential in character and producing for the most part only slight 

 effect on the tree-growth. To the east is the Rocky Mountain zone, 

 which catches a remnant of the coastal variations and gets its chief 

 moisture supply in summer. 



Latitude effect — In each of these zones there is a strong latitude 

 effect. On the coast the westerlies are very powerful in the higher 

 latitudes, weakening south of San Francisco and becoming gentle at 

 San Diego. They disappear entirely in the tropics. In the valleys of 

 the central zone the spring rainfall maximum of the north changes to 

 the well-defined winter and summer rainy seasons of Arizona. The 

 eastern or Rocky Mountain zone has less latitude change than the 

 others. The total rainfall increases as we go south by the increasing 

 amount of summer rains. In Texas, and still more in Mexico, it 

 begins to show a temporary diminished rainfall in July and August 

 at the very peak of the maximum. Perhaps this is actually the tropical 

 winter minimum of the southern hemisphere reaching over thus far 

 into northern latitudes. 



THE PUEBLO AREA 



The Pueblo area trip was made in behalf of the National Geo- 

 graphic Society in connection with studies of the Pueblo Bonito 

 chronology. It seemed advisable to visit and test the pine and spruce 

 regions from which the prehistoric Indians drew their timbers and 

 find out whether such regions agree with the Flagstaff areas in their 

 tree-growth. 



The Hopi villages — These villages, still occupied, he along the 

 southern edge of a raised and sloping plateau called the ''Black 

 Mesa," whose surface is dissected by canyons and whose highest 

 point, some 75 miles north of the villages, is near Kayenta. 



Kayenta — The 24-hour trip from Flagstaff to Kayenta was made 

 on September 4 and 5, 1926. The settlement is in a valley just east 

 of Mount Lolomai, the highest point of Black Mesa. Mr. John 

 Wetherill, for many years well known in this region, took us to the 

 mountain top, 4 miles in a car, 4 or 5 more on horseback, and then a 

 climb of 700 feet on foot. Samples collected in several different places 

 all show the Flagstaff ring record, as do the rings in the beams of the 

 Wetherill house. 



On September 7 we started to Chin-lee, 72 miles southeast, pass- 

 ing Chilchinbeto at 16 miles and confirming the agreement between 

 Black Mesa and Flagstaff by some specimens there.* At Chin-lee 

 we cut radials from logs in the store of Mr. L. H. McSparron, who very 



♦Later, on the return trip, we stopped at Oraibi, the westernmost of the Hopi villages, and 

 cut radials from logs of spruce from Pinon, 30 miles northeast, with the same result. 



