Twenty-four samples of CO2 from combustion of the NBS oxalic-acid radiocarbon standard, submitted from 13 radiocarbon laboratories, were analyzed for C13 content in this laboratory in order to provide comparative data for normalizing the counting results. The samples were analyzed on Samson, a 60° sector, six-inch radius, McKinney-Nier type mass-spectrometer with magnetic switching between sample and standard gas feed to the instrument.

With one exception, the radiocarbon dates in this list were reported previously by Rainey and Ralph (1959). For discussions of the reliability of the dates, of the materials dated, and of the correspondence of the dates with estimated arctic chronologies, the reader is urged to refer to the original publication. The radiocarbon determinations were made over a period of several years. Those processed before 1956 were dated by the solid-carbon method and are so labeled; others, by the carbon-dioxide method. The age calculations are based on the average of several samples dated archaeologically and by tree-rings, corrected to zero age (Rainey and Ralph, 1959, p. 365). By this means the errors due to atmospheric depletion (Suess effect) and to past changes in radiocarbon concentration (de Vries, 1958; Willis, Tauber, and Münnich, 1960) have been minimized. The b.p. dates are calculated from A.D. 1957 (solid-carbon) and A.D. 1958 (carbon dioxide).

This list covers measurements made at the Radiocarbon Dating Laboratory, Physics Department, University of Bern, from spring, 1959, until summer, 1960. We have now two low-level counters working (Houtermans and Oeschger, 1958).

A C14-dating installation was operated in the Physics Department, Trinity College, Dublin, from early 1958 until early 1960, by I. R. McAulay. Construction and testing of the apparatus had occupied 15 months previous to this. Material for dating was selected and pretreated by W. A. Watts, who also collected and submitted the samples and carried out pollen analyses except where the contrary is stated in the text. The project was a short-term one with two main aims; to obtain a few key archaeologic dates, particularly in the Neolithic, to help orientate chronologic discussion; and to test the validity of the pollen zonation for the post-Atlantic of Mitchell (1956).

The third series of radiocarbon measurements made at the British Museum Research Laboratory is reported in the following list. Equipment and method used are as described previously (British Museum I) and, as in previous lists, the error terms are not based solely on counting statistics, but are widened to include contributions of ±80 years for possible isotopic fractionation effects and ±100 years for the de Vries effect. Ages are calculated on a half-life of 5568 ± 30 years. NBS oxalic acid is now used as a reference standard in place of 100-yr-old oak. The latter gave an age-corrected value almost exactly 95% of the oxalic-acid activity and thus no corrections are required to our previous date lists to bring them into line with the new standard.

A complete description of the CO2-CS2 Geiger-counter system which is in operation at the University of Michigan Radiocarbon Dating Laboratory is available in mimeograph form, upon request to the author. It includes a report on research into the characteristics of the CO2-CS2 counter, as well as a full set of instructions and diagrams for the building of such a system for use in radiocarbon dating.

Radiocarbon analyses have been performed at Isotopes, Inc. since 1957 using proportional-counting techniques. Carbon dioxide is employed as the counting gas at pressures up to two atmospheres. The counter presently in service is electrolytic copper and has an active volume of just under two liters. It is shielded by one in. of mercury, a ring of 23 G-M counters operated in anti-coincidence with the sample counter, 4 in. of paraffin wax, and 18 in. of hot-rolled steel. A background of 9.2 counts/min has been attained with this arrangement.

The dates and activity measurements given below have been obtained during the year 1960 (excepting only Q-9 held over from the previous year). They have been made with carbon dioxide at 3 atmospheres pressure in a proportional gas-counter similar to that used for the results given in Radiocarbon Supplement, volumes 1 and 2.

In continuance of investigations upon successive annual crops of oats reported in Radiocarbon Supplement, Volume 2, we undertook the analysis of successive annual rings of a tree that had been growing throughout the period covered by the oat-crop assays, namely 1953 to 1959. The selected tree was a straight-boled specimen of Populus nigra from the Forestry Commission's plantations at Santon Downham, near Thetford, Norfolk. It had been planted in 1929 and was felled on 21 October, 1959. Shortly afterwards, it was brought into the laboratory and sawn into slices just over 1 in. thick. The surfaces having been smoothed, the annual-ring contacts were marked, and within each annual ring the inner (spring) wood was marked off from the outer (autumn) wood. The tree had been chosen as one exhibiting rapid growth and it proved fairly easy to dissect off with a chisel all the separate half-rings between spring 1953 and the end of 1959. In the event, activities were determined only upon four of the half or whole rings.

The following list covers samples measured at the Uppsala radiocarbon laboratory during 1960. The technique used has been described by the senior author (Olsson, 1958). Pretreatment has not been changed since the last dating list was published (Uppsala II).

Dates in this list have been determined at U. S. Geological Survey radiocarbon laboratory, Washington, since our 1960 date list (USGS V). Procedures for the preparation of acetylene gas used in the counting, and the method of counting, (two days in two separate counters) remain unchanged. However, the modern standard used is no longer wood grown in the 19th century, but 95% of the activity of NBS oxalic-acid radiocarbon standard, as recommended at the 1959 Groningen Radiocarbon Conference. Measurement of the oxalic-acid standard at our laboratory indicates 6.2 ± 1% more C14 activity than our modern wood standard; so use of the new standard should make no appreciable difference when comparing samples computed by the old method. W. F. Libby's (1955) half-life average for C14, 5568 ± 30 years, was used for the decay equation.

Almost all radiocarbon measurements reported in the following list have been made with the same equipment and method used for the measurements reported in our previous work (Pisa-I). The sample used as contemporary standard for these samples is also charcoal obtained from Arbutus unedo wood grown near Pisa between 1948 and 1956. The value obtained from this standard has also been used for shell samples.

The following is a list of radiocarbon dates obtained since the preparation of the manuscript for the publication of Michigan V, in December, 1959. The method of measurement and treatment of data are the same as those described in the introductions to Michigan lists III and IV. A full statement on the Michigan counter is referred to by Crane (p. 46) in this issue.

The following list includes most of the measurements made since publication of Yale V; some measurements, such as a series collected in Greenland by A. L. Washburn, are withheld pending additional information or field work that will make better interpretations possible. In addition to radiocarbon dates of geologic and/or archaeologic interest, we give in the third part of the paper, for the first time since 1954 (Deevey and others, 1954), recent assays of C14 in lake waters and other lacustrine materials, now normalized for C13 content. Some of these C13 values have been published separately (Oana and Deevey, 1960), but most have not.

Radiocarbon-age measurements reported here were made at Lamont Geological Observatory between July 1958 and November 1960. Sample descriptions are classified as follows:

1. I. Samples associated with glacial deposits

2. II. Samples associated with marine coastal deposits

3. III. Samples associated with marine coastal deposits uplifted by glacial rebound

4. IV. Samples associated with pluvial-lake deposits

5. V. Samples from deep-sea cores

6. VI. Samples from cave deposits

7. VII. Miscellaneous samples of geologic interest

8. VIII. Samples of archaeologic interest

Like Lamont VI (Broecker and Olson, 1959), this list contains only results on samples of known age (most of which formed during the past ten years). The measurements were made largely in order to gain an understanding of the distribution of radiocarbon within the dynamic carbon reservoir. Again, the data are not reported primarily with the idea of drawing new conclusions but rather to bring together in one place information which is presently scattered throughout the literature or which otherwise might remain unpublished.