= Solution
\b[The 1864 solid units are the <avoirdupois pound>, <avoirdupois ounce> and <grain>; the liquid units are the Imperial measures.] The <grain> is unchanged, while the old apothecaries' pound and ounce are not the units of the new formulary. <The Prescriber's Analysis of the British Pharmacopoeia by John Birkbeck Nevins (1864)>[pp. 16–17, change of weights and unchanged liquid measures]{ref}
The relations for solids are
$$
1\,\mathrm{lb}=16\,\mathrm{oz}=7000\,\mathrm{gr},\qquad
1\,\mathrm{oz}=437.5\,\mathrm{gr}.
$$
Their approximate French metric equivalents are:
* one <grain>: $\boxed{0.0648\,\mathrm{g}}$, about $64.8\,\mathrm{mg}$;
* one <avoirdupois ounce>: $\boxed{28.35\,\mathrm{g}}$;
* one <avoirdupois pound>: $\boxed{453.59\,\mathrm{g}}$.
For liquids,
$$
1\,\mathrm{gal}=8\,\mathrm{pt},\qquad
1\,\mathrm{pt}=20\,\mathrm{fl\,oz},\qquad
1\,\mathrm{fl\,oz}=8\,\mathrm{fl\,dr},\qquad
1\,\mathrm{fl\,dr}=60\,\mathrm{min}.
$$
The approximate metric volumes are:
* one <minim>: $\boxed{0.0592\,\mathrm{mL}}$;
* one <fluid drachm>: $\boxed{3.552\,\mathrm{mL}}$;
* one <fluid ounce>: $\boxed{28.41\,\mathrm{mL}}$;
* one <Imperial pint>: $\boxed{568.26\,\mathrm{mL}}$;
* one <Imperial gallon>: $\boxed{4.5461\,\mathrm{L}}$.
A <millilitre> is a cubic centimetre, and a <litre> is a cubic decimetre. These displayed equivalents are rounded; small differences from a period table's last digits reflect rounding and historical calibration conventions. A <fluid ounce> is a <volume> and an <avoirdupois ounce> is a <mass>. They cannot be interchanged for an arbitrary liquid without its <density>. Likewise, a drop is not a defined <minim>: its volume depends on the liquid and the dropper.
<NIST Guide to the SI>[Appendix B.8, grain, avoirdupois pound and ounce, Imperial gallon and fluid measures; modern rounded metric conversions]{ref}
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