This section is from the book "The Tinman's Manual And Builder's And Mechanic's Handbook", by Isaac Ridler Butt. Also available from Amazon: The Tinman's Manual And Builder's And Mechanic's Handbook.
Rule. - Take the dimensions, in inches and decimal parts of an inch. Square the diameter, multiply it by the length in inches, and then multiply the product by .0034 for Wine Gallons, or by .002785 for Ale Gallons.
Example. - How many U. S. Gallons will a Cylindrical Vessel contain, whose diameter is 9 inches, and length 9½ inches?
or 2 gallons and 5 pints.