Peter Borst writes: <<When someone says 5 cells to the inch, what is the level of accuracy? Were it 4.9 or 5.1 cells to the inch, would they round it to 5? When someone writes 5.01 mm, they are signalling a high level of accuracy, but Root refers to 5 to the inch, and 3 1/2 to the inch, indicating a rather broad brush -- not very subtle differences.>> Perhaps not all that broad. The 1917 ABC & XYZ discusses the variation in cell size which can be 'shown by careful measurement', and differentiates between natural comb, at 28 13/15 cells to the square inch, and comb built on foundation, at 27 per square inch. Wedmore (1946) differentiates between foundation measuring 'five cells per inch' and that measuring 4 3/4. I think the fact that they made these distinctions indicates that their measurements were more accurate than you suggest; the difference between 4.9 and 5.4 is greater than this. Could there be a piece of old comb preserved in some museum somewhere? Has anyone tried to find out? Given the Victorians' habit of preserving all sorts of specimens, it would almost seem surprising if there's nothing sitting in a bottle in a back room somewhere. Regards, Robert Brenchley [log in to unmask] Birmingham UK