Problems of the statistical interpretation of radiocarbon age measurements of old samples are discussed, based on the notion of fiducial probability distribution. A probability density function of age has been given. A detailed discussion of different facets of the probability distribution of age has led us to the confirmation of the use of 2σ as the best limiting value between the regions of finite and infinite dates. It has been proposed to make use of the principle of constant probability P = 0.68 in the regions of both finite and infinite ages instead of the criterion N + kσ.

The dating equipment and operating procedures in the Physical laboratory remained as described previously (R, 1974, v 16, no. 1, p 6-9).

Dates were calculated using the 5568-year half-life with 1950 as the reference year, the modern standard being 0.95 of the activity of the NBS oxalic acid standard. When done, δ13C was measured on CO2 produced in the combustion of samples, and results are given relative to the PDB standard. All samples were from Ireland.

This date list covers a selection of 14C results of hydrologic samples investigated from January 1978 until August 1979. According to convention, the ages were calculated with a 14C half-life of 5568 yr and 0.95% of the activity of NBS oxalic acid standard and are quoted in years before 1950. The recent activity of water is assumed to be 90% modern (Geyh and Kreysing, 1973) and corrections for 12C/13C isotopic fractionation have not been made.

The following date list covers samples dated by the La Jolla Radiocarbon Laboratory during calendar year 1978. All archaeologic, all geologic, and some geochemical and botanical samples measured during that period are included here. Recent measurements of 14C in tree rings and in annual coral rings will be published elsewhere. Plots and discussion of data for corals from Belize and Florida have been published already by Druffel (1980).

Most of the 14C measurements reported here were made between October 1978 and October 1979. Equipment, measurement, and treatment of samples are as reported previously (R, 1968, v 10, p 36-37; 1976, v 18, p 290) except for some minor improvements of the electronic equipment. Sediment samples too small to allow pretreatment, are now burned at <650°C in order to avoid pyrolysis of carbonates that may be present in the samples. Same max combustion temperature is used for samples with suspected graphite contamination. A movable thermocouple (Philips TERMOCOAX TCI 30/50/3) in the combustion zone is used for checking the temperature.

The following list includes some measurements made during 1978 and 1979 in the radiocarbon laboratory of the Ecole Nationale Supérieure de Géologie Appliquée et de Prospection Minière (ENSG) de Nancy. Equipment, measurement and treatment of samples are as reported previously (R, 1979, v 21, p 453-464) where the sample is synthesized to benzene. Radiocarbon ages are calculated using the 14C half-life of 5568 years and 95% activity of NBS oxalic acid is used as modern standard. Anthracite coal and Merck commercial benzene are used for the dead carbon run.

This list contains analyses completed between January, 1976 and April, 1977. Details of laboratory operation are contained in our first list (R, 1975, v 18, p 205). Samples submitted for analysis are reviewed by a committee consisting of W DeBoer, E Hansen, Anthropology; L Marcus, Biology; W S Newman, D L Thurber, Earth and Environmental Sciences; and Richard Pardi, Radiocarbon Laboratory.

The present list includes 74 dates of geologic samples determined using the liquid scintillation 14C method at the Geobiochemical sector of the Institute of Zoology and Botany, Academy of Sciences, Estonian SSR.

This list reports certain 14C measurements completed by December 1979; other projects completed by this time will be reported later. Age calculations are based on 14C half-life of 5568 yr and modern standard of 95% NBS oxalic acid, supplemented by tree rings of pre-industrial wood from a log cut in the 1850's (Tx-540; R, 1970, v 12, p 249). Deviations reported are based on counting statistics of sample, background and modern, and are ± 1σ, except that when sample count approaches either modern or background, 2σ limits are reported. Unless noted, 12C/13C measurements were not made and results are not corrected for 13C fractionation (assumed ratio = −25‰ WRT PDB). Our laboratory uses liquid scintillation counting of benzene, with Li2C2 and vanadium-activated catalyst in preparation; chemical yields range between 95% and 99%. Three counters are employed; a Packard Tri-Carb Model 3002 and 2 Beckman LS230 spectrometers obtained through a grant from the National Science Foundation.

The following radiocarbon dates are a partial list of samples measured for a variety of projects and materials since August 1979. Chemical and counting procedures remain the same as indicated in R, v 20, p 274-282.

The following radiocarbon dates are a partial list of samples measured for a variety of projects and materials since January 1980. Chemical and counting procedures remain the same as indicated in R v 20, p 274-282.