Hugh Farey wrote:
. . . Dr [A. J. Timothy] Jull [pictured] has confirmed that two of the four samples were indeed retained, and the other two were cut into two again, making four samples of between 5mg and 7mg for dating. I have not pressed him on whether this was actually sufficient.
Does anybody know how much the Oxford or Zurich labs used, or whether they too kept back half their sample for further research and/or confirmation of the results.
There were several other comments and then David Mo asked if Hugh had a problem with Dr. Jull’s answer. To that, Hugh wrote:
Not at present, no. I simply want to know how many mg of an unknown fabric was considered necessary to achieve a dating measurement in 1988. There is carbon dating submission advice online (http://www.ess.uci.edu/ams/Sample%20Submission%201.htm), from the University of California, currently asking for 2.5mg of dry weight carbon-rich organic material. If that was the case 25 years ago, then the dating procedures carried out by Arizona seem to me beyond reasonable reproach.
David Mo continued:
This is important information that you have obtained, Hugh. It changes many hypotheses. May we have some literal quotation from Jull’s writing/e-mail?
This is it, a lot of literal quotation, a fantastic contribution by Hugh to our knowledge about them samples in Arizona. Hugh comments:
In his email to me, Dr Jull writes [my notes in square brackets]:
[This measurement was therefore made in Turin.]
These were subdivided into a. 13.86mg, b. 12.39mg, c. 14.72mg and d. 11.83mg. Obviously, these total 52.8mg not 53.7mg. The discrepancy was attributed by us to a weighing error, when the original sampling was undertaken.
[These measurements were therefore made in Tucson. Jull assumes the Turin measurement was wrong. There may have been some drying out.]
You are correct that last two of the pieces (c and d, as labelled above) were used for the dating and they were subdivided into two – making a total of four discrete samples for dating.
[The mass of the ‘extra sliver’ was originally given as 14.2mg by Riggi, but it could be piece (a) above if it had dried. The mass of the largest tested sample could not have been more than 7.36mg.]
Each of these 4 samples was processed as separate samples. In each case, the resulting graphite was run twice, resulting in 8 independent determinations. I think that the 2 determinations on each sample were combined in the Nature paper, but that the original data was provided to Dr. Tite, who was coordinating the publication.
The remaining material was retained in case of future work to reproduce the results, as is normal practice in any laboratory.
[If so, then presumably the Oxford and Zurich labs did the same. I have not heard from Dr Ramsey or Dr Bonani yet.]
For continuity, let’s try to keep the comments going at the Special Request from Hugh Farey posting and not have comments here.