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Such records in living trees — now some 500 years in Alaska and 600 years in Canada — may be greatly lengthened by certain relative sequences of dates in archaeological material. Growth patterns can be identified as easily in cut logs and dirftwood as in living tree.

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As in the case of driftwood, the time between the death of a tree and its eventual use by an Eskimo cannot be determined, dating of this sort offers time stops after which occupation and abandonment of a site must have occurred.

A careful study of available bark dates, however, often delineates more closely the occupation of a site, partly through indicating a period after which driftwood was no longer used in that particular site.

A mean curve of June-July temperatures from all Yukon Valley weather stations agrees closely with tree-growth curves from timber-line areas near the 3,000-feet level in the Alaskan interior and with tree-line outposts at sea level on Seward Peninsula and on the Noatak and Kobuk rivers, but the mean July temperatures recorded at the Aklavik weather station on the Mackenzie Delta come nearest to the record shown by trees growing in that vicinity.

The measure of agreement between tree-ring fluctuations and weather records is greatly limited by the recency of weather recording throughout this part of the North.

Corroborative evidence comes, however, from recent extensive research by Scandinavian workers.

They have shown that, at the northern forest border in Norway, Sweden, and Finland, pine and spruce trees have responded closely to June or July temperatures, or a combination of the two, during the long span of Scandinavian weather recording.Verification in driftwood demands longer individual sequences of rings and more specimens covering the same time span.For instance, the thin ring pattern of 1910-1912-1919 may be verified in two living trees less than 50 years old by counting back from the known outer ring, but between two driftwood logs all such patterns may need to be traced over a span of more than 100 years to rule out chance agreement.The valley trees carry a variant set of ring patterns which can be readily crossdated either up or down the river, but not with neighboring trees at the high elevations.Separate chronologies which have been worked out for these river-bottom areas are often of high dating quality, but their climatic meaning is obscure.Chronologies in t ree rings are built by crossdating either living trees or dead logs, but if only dead material is used the dating remains a relative or “floating” chronology until it is identified with a living-tree chronology for which dates of the Christian era are known. Andrew Ellicott Douglass and his students and associates, but certain extensions and special techniques are necessary in elucidating the problems of the North.

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