CHRONOLOGY DOUGLASS AND ANTEVS 311 



plete identity between this extension and the late prehistoric rings 

 was firmly established. Thus the problem was solved. To our sur- 

 prise there was no gap, but an overlapping of more than 20 years. It 

 had been impossible to recognize this on account of the great drought 

 in the late 1200's, which rendered most trees badly defective. Nat- 

 urally, with so many defects during that drought interval, it has 

 been gratifying to see since then tree records both in the Sierra 

 Ancha Mountains of Arizona and others on the east slopes of the 

 Jemez Mountains in New Mexico which check with precision the 

 identity assigned to the rings in that great drought. 



This solution gave at once the dating of 42 ruins ; the number has 

 now reached 75, scattered over northern Arizona, northern New 

 IMexico, and the southern edges of Colorado and Utah. Many of 

 these were built just before the great drought in the late 1200's. 

 Evidently that climatic catastrophe had a profound effect on the 

 welfare of the primitive inhabitants. Many ruins northeast of 

 Flagstaff dated in the llOO's, and one at least lasted until 1278. The 

 great tower in Mummy Cave ruin, in Canyon del Muerto, dated in 

 the early years of the drought. White House ruin in Canyon de 

 Chelly, came before 1100, as did Cliff Palace and the earlier ruins 

 of Mesa Verde. Other ruins in Mesa Verde were built during the 

 following 200 years. Aztec, in northwestern New Mexico, with its 

 450 rooms, was built in the dozen years between 1110 and 1122. 

 Pueblo Bonito, the largest of them all, had its early construction 

 between 919 A. D. and 950. Its major building was in the last half 

 of the eleventh century, and its final construction extended into the 

 early years of the twelfth century. 



Thus, in closing the gap, the chronology was extended back to 700 

 A. D. Nearly every portion of it has been covered by at least 100 

 specimens. Much of the eighth century from 735 to 800 A. D. has 

 now been covered by a considerable number of specimens from the 

 vicinity of Flagstaff, collected by Dr. Harold S. Colton, director of 

 the Museum of Northern Arizona, and his colleagues. And yet only 

 one specimen, and that from Pueblo Bonito, covers with accuracy the 

 years from A. D. 700 to 735.^ Meanwhile further extensions are 

 under way. Groups of specimens, collected chiefly by Earl H. 

 Morris, have given two long sequences totaling over 600 years, which 

 seem at present to precede the known chronology, beginning at 

 700 A. D. 



One of the very interesting studies now in progress is being carried 

 on by Doctor Colton, on pit houses near Flagstaff, Ariz., which were 

 covered by a 10-inch layer of cinders from an eruption of Sunset 



1 Since this was written Miss P. M. Hawley has dated a beam from Chettro Ketl that 

 extends our record back to A. D. 643. 



