This list covers part of the samples measured at the Radiocarbon Dating Laboratory, Physics Department, University of Bern since summer 1962. Two low-level counters, as described by Houtermans and Oeschger (1958), with incorporated anticoincidence are used. Each sample is measured in both counters. The CO2 from the sample is converted to methane by pumping a (CO2 + H2)-mixture at a pressure below 1 atm over a Ru-catalyst at 200°C.

This list includes many of the datings done from November 1963 to October 1964. The instruments and techniques used for this work are essentially the same as those used previously (Gakushuin III).

Most of the determinations reported here were obtained with the 2 L counter described in our first date list (GSC I). All age calculations are based on a C14 half-life of 5568 ± 30 yr and 0.95 of the activity of the NBS oxalic-acid standard, and the ages are quoted in years before 1950. The age errors include: counting errors of sample, background, and standard, the error in the half-life of C14, and an error term to account for the average variation of ±1.5% in the C14 concentration during the past 1100 yr. ‘Greater than’ ages are based on the 4 σ criterion (GSC II).

Geochron Laboratories, Inc. C14 facilities began operations in April 1963. Some of the results obtained during the past year have been released by our clients and are presented below.

The I.V.I.C. laboratory started operation in December, 1963 using liquid scintillation techniques and the benzene method. The syntheses are carried out in a Packard benzene synthesizer and the solutions counted by a Packard automatic tri-carb spectrometer. For routine dating, a 4 cc counting vial is used with 2 cc benzene coming from the sample being dated and 2 cc commercial toluene added with the PPO and POPOP scintillators.

During 1963 and 1964 the La Jolla Radiocarbon Laboratory continued to follow essentially the same techniques as in previous years. The three counters described in La Jolla III have continued to yield measurements in virtually complete agreement. As before, we add, except for the measurements of apparent age on organisms collected alive (see below), ca. 100 yr to the one-sigma statistical counting error. Dates are still computed on the basis of the half-life estimate of 5570 yr.

The following list covers the samples measured at the Louvain C14 dating laboratory in 1964.

The following is a list of dates obtained since the time of the compilation of List IX in December 1963. The method is essentially the same as that used for the work described in the previous list. Two CO2-CS2 Geiger counter systems were used. The equipment and counting techniques have been described elsewhere (Crane. 1961a, 1961b). The dates and estimates of error in this list follow the practice recommended by the International Radiocarbon Dating Conference of 1962, in that (a) dates are computed on the basis of the Libby half-life, 5570 yr, (b) a.d. 1950 is used as the zero of the age scale and (c) the errors quoted are the standard deviations obtained from the numbers of counts only. In previous Michigan date lists up to and including VII we have quoted errors at least twice as great as the statistical errors of counting, in order to take account of other errors in the over-all process. If the reader wishes to obtain a standard deviation figure which will allow ample room for the many other sources of error in the dating process, we suggest he double the figures that are given in this list.

A systematic error of calculation has been included in all radiocarbon age figures released from this laboratory (Miami I, II, and III). The error affects dates of all materials, organic and inorganic, terrestrial and marine, in the same way, namely making them about 410 yr too young. Instead of adding to the confusion by correcting the old age figures we preferred to recalculate the dates starting from the measured isotope ratios. Table 1 below reports the correct age figures as calculated in the following way:

The following list comprises measurements made since those reported in NPL II and is complete to the end of November 1964.

The dates listed were obtained using a stainless steel counter with an active volume of 1.3 L and a background of 16.3 cpm at an absolute filling pressure of 152 cm Hg. The present proportional counter in use is made of O.F.H.C. copper, and has an active volume of 1.25 L and a background of 5.2 cpm, at an absolute counter filling pressure of 152 cm Hg. CO2 is used as the counting gas and the counter is filled to a pressure of between 76 cm and 228 cm of Hg (depending on the sample size) at a temperature of 23 ± 0.3°C. The counter is shielded, starting from the top, by 5 cm of lead and 26 cm of iron, and is surrounded by an array of 22 Geiger tubes, and then finally by 2.5 cm of mercury. The thickness of the sides and base is greater than 10 cm of iron. As yet no neutron shielding is used and this probably accounts for the large fluctuations of background with barometric pressure (0.32 cpm per 1 cm Hg change in the pressure).

The following is a list of dates obtained since the compilation of our first list in November, 1963. Equipment and operating procedures are the same with the exception that a gas chromatograph has been added to confirm the purity of the methane samples used for dating.

The radiocarbon dating laboratory at the USDA Sedimentation Laboratory was established to supplement current watershed geomorphologic investigations. The principal objective of the program is to provide information on valley aggradation rates and sequences.

Measurements of samples of known age have been undertaken in this laboratory since its beginning in 1951 when it was found that modern wood samples taken from the outer rings of young trees did not afford a basis of counter calibration consistent with archaeologically dated samples (Ralph, 1955). This depletion was explained by Suess (1955). Subsequent measurements of samples representative of the early Egyptian dynasties, however, revealed that even with the counter calibration corrected for the modern depletion, there was a discrepancy between C14 dates and the early Egyptian chronology (Arnold and Libby, 1951; deVries, Barendsen, and Waterbolk, 1958; deVries and Waterbolk, 1958; Barker and Mackay, 1959, 1961; Ralph, 1959; Damon and Long, 1962). Obviously, there was, and still is, a need to find samples of known age for this time range. Dendrochronology may ultimately provide the answer, and in the meantime tree-ring dated samples have afforded a means of assessing the atmospheric C14 inventory during the last 3000 yr.

This date list includes those series of archaeologic samples completed in this laboratory during 1963 and 1964. The b.p. ages are calculated from a.d. 1950, and are based upon a half-life value of 5568 yr. Errors quoted do not include the half-life error. All samples have been pretreated with 3N HCl, and some, where noted, have received an additional 2% NaOH pretreatment for the removal of possible humic acid contaminants.

The Low Level Counting Laboratory of Packard Instrument Company was organized and began operations in the fall of 1963 with the development and construction of the Packard Tri-carb® Benzene Synthesizer. This instrument is designed to consolidate into a small area (6 ft × 8 ft) the equipment necessary to quickly and efficiently convert carbon-containing material or tritium water samples into benzene—an ideal solvent for liquid scintillation counting.

The dates and activity measurements given below have been obtained during 1963 and 1964, and have been made with CO2 at 3 atm pressure in a proportional gas-counter as described in previous contributions from this laboratory. We have again concentrated chiefly upon research projects pursued in the University Sub-department of Quaternary Research, but have continued final determinations also in the series of samples of CO2 collected in the lower stratosphere and described in our date list VI.

The following list comprises age measurements carried out between December 1963 and September 1964. The samples dated are almost all of archaeological interest and are drawn from Italian and Egyptian territory.

This report covers the investigations of the Laboratory of Archeological Technology of the Institute of Archeology of the Academy of Sciences of the U.S.S.R. under the technical direction of Corresponding Academician I. Ye. Starik. This work was begun in 1956, but the bulk of the dates were obtained during 1959–61 by the ethyl-benzol technique. For a control, ethyl-benzol was synthesized from the annual rings of the heartwood of an 80-yr-old larch. Depending on the size of the sample submitted for analysis, from 15–70 ml of ethyl-benzol was used.