Tipping points.

In "Original Microbrews" (SN: 10/2/04, p. 216), several statements regarding my archaeological-chemical research are inaccurate. Very good evidence for barley beer has been obtained, as my laboratory published in 1992 (SN: 11/5/92, p. 360). In short, calcium oxalate--known to brewers as beerstone because it easily precipitates during the course of making barley beer--was identified as constituting a distinctive residue inside a jug from Godin Tepe in Iran, dated to 3500 B.C. to 3100 B.C. With regard to wine, your article implies that tannins in ancient samples were preserved and identified. This is yet to be accomplished. Rather, our focus has been on biomarkers for grapes and wine (tartaric acid) and tree-resin additives to the beverage. Finally, whether the Schinus molle berries found in a trash pit close to the Peruvian "brewery" uniquely yield large amounts of oxalic acid and were used in brewing a beverage remains to be proved.

PATRICK MCGOVERN,

UNIVERSITY OF PENNSYLVANIA,

PHILADELPHIA, PA.

Surely, you mean ale. Beer, in this country at least, is a hopped drink. Evidence of ale brewing is what Robin Birley found at Vindolanda. Beer didn't appear in England until the late Middle Ages.

RON WILCOX, BATH, ENGLAND