Ɛpsilon

From E. A. Darwin   [c. 22 November 1875]1

Dear Charles

The Useful K. Almanac does not contain fluid measure as used by Apothecaries & the London Pharm:2 says nothing (for us), except that the pint contains 20 oz. Taking the oz as 120 of pint it = 437.5 grs the same as you have it & the pint 114 lb. The rest is hypothetical if P’ = old pint = 1 lb (as we thought) then

P’/16 = P(imperial) /20, or

16 oz (of 437.5 grs) = old pint

20 oz (of Do) = imperial pint

I looked in my old Duncan & found the same discrepancy underlined.3

It is enough to make one swear | E D

1
The date is established by the relationship between this letter and the letter to J. V. Carus, 22 November [1875].
2
The British almanac for the Society for the Diffusion of Useful Knowledge was published annually from 1828 by Baldwin and Cradock. Apothecaries weight was a system of measurement officially superceded in 1826 by the imperial system; similarly, the capacity measurements of the London pharmacopoeia were superceded by those of the imperial system (5. George IV. cap. 74). Because the systems coincided in some, but not all, measurements, there was often confusion if the system used was not specified.
3
Andrew Duncan, in an appendix to the Edinburgh new dispensatory (Duncan 1830, pp. 109–34), gave tables of equivalents for the various English measuring systems and the continental metric system.

Please cite as “DCP-LETT-9197,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-9197