Schulman • Tree-rings and History in the Western United States 185 



ity from tree to tree as shown in the archaeological wood. A number of 



figure is quite unlikely to be found, floating chronologies were developed, 



even in trees of one species and within built up of ancient beams which cross- 



a small locality. dated with each other but which could 



In many species and individual not be joined to the dated rings of the 



trees, the rings are so complex and living-tree master record; a gap of un- 



variable that cross-referencing with known length had to be bridged. At 



other rings is not possible. Indeed, the last beams were obtained which did 



botanist is familiar with so many rea- overlap the inner part of the master 



sons for such ring irregularity— specific chronology, and immediately dates 



characteristics, environmental influ- could be assigned to several scores of 



ences, accidental events, and so on— ruins in the Southwest. The most 



that close parallelism in ring fluctua- magnificent of these, the apartment 



tions among different trees might well houses of the "cliff dwellers," as at 



seem the rare exception. It was fortu- Mesa Verde National Park, were 



nate for the pioneer work in dendro- among the most recent, principally in 



archaeology that it was applied in the the 1200's a.d. 



Southwest, where species, climate, site The 1929 "Crossing of the Gap" 



and wood collecting by the ancients all initiated a period of intense activity 



so happily favored the research. It in dendro-archaeology. Earlier and still 



should not be supposed, however, from earlier ruins were dated in the Central 



the foregoing that such cross-dating is Pueblo area; independent master 



a characteristic only of certain South- chronologies were developed for the 



western trees. This property has now Rio Grande by W. S. Stallings and for 



been found present in many other re- northeastern Utah by Schulman; and 



gions, though nowhere in such good now the dates of several hundred ruins 



form in so many trees. and a chronology for the Southwest 



The tendency of the ring-widths in reaching back 2,000 years have been 

 dominant conifers of the Southwest— estabhshed. By similar methods dates 

 Pseudotsuga menziesii, Pinus ponder- have been obtained by various investi- 

 osa, P. edulis— to show approximately gators for less ancient works of man in 

 the same patterns over a large area Norway, Sweden, Germany, and par- 

 made it significant to take broad-scale ticularly, by J. L. Giddings, in Alaska, 

 averages of many trees and thus derive As an example, we may note a re- 

 a so-called master chronology. In this cent application (1952) of this method, 

 way local peculiarides in growth were namely, the extension of the Puebloan 

 minimized and the master chronology chronolog}' into b.c. times. The ring 

 served as a general standard, against sequence in a very sensitive and con- 

 which beams from widely separated lo- sistent ancient beam of Douglas-fir 

 calities could be dated. from Mummy Cave, northeastern 



The development from living trees Arizona, was definitely dated by com- 



and relarively recent house beams of a parison with master chronologies and 



master chronology which extended with individual specimens long dated 



back into the time of the prehistoric and available for several localities in 



Pueblos was not accomplished at once that area. 



—the daring of the Cliff Dweller This extension of the known chro- 



ruins, announced by Douglass in the nology then made possible the dating 



National Geographic Magazine in De- of a number of short charcoal frag- 



cember, 1929, was preceded by over mcnts from an early archaeological 



a decade of collection and analysis of site near Durango, Colorado. Among 



