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H. 4¼" 10.8cm, rim d. 2¼" 5.6cm, base d. 2¼" 5.7cm, weight 6½oz 190g. Sowerby's white vitro-porcelain. Upright rim as shown in Pattern Book IX, also known with flared rim — see photograph in Cottle. Nice clear Sowerby TM in the centre of the base. No registration lozenge in common with designs copied from other sources — J.G. Sowerby followed the rules.
This pattern is a close and accurate copy of "M" — Multiplication in Walter Crane's
Baby's Own Alphabet, 1875. The only significant change was the addition of a chequered background. There are 30 squares around the vase, split into 7½ on each of the four side mould sections, and hiding most of two mould lines. Why not 32, which would have hidden all four? Puzzling.
The illustration in the book is accompanied by Crane's version of the old Multiplication rhyme:
M | ULTIPLICATION is vexation, Division is twice as bad. | | The Rule of Three it puzzles me, And Fractions drive me mad. |
Each line of the verse matches a view of the same schoolboy with slate and pencil, all four on the same extended bench. On the chequered background numbers and mathematical symbols have grown arms and legs, turning them into mischievous sprites or elves.
The Rule of Three was notorious for being particularly difficult to explain. Here is how Cocker's Arithmetick, the premier textbook in the 17th century, and used by such worthies as Benjamin Franklin and Samuel Johnson, approached the subject:
| Again, observe, that of the three given numbers, those two that are of the same kind, one of them must be the first, and the other the third, and that which is of the same kind with the number sought, must be the second number in the rule of three; and that you may know which of the said numbers to make your first, and which your third, know this, that to one of those two numbers there is always affixed a demand, and that number upon which the demand lieth must always be reckoned the third number. | |
Any the wiser? No, neither am I.

This is a real gem from Sowerby, and made me laugh when I first examined it. I hope you like it.
Bernard C.

See Cottle, Simon,
Sowerby — Gateshead Glass, Tyne and Wear Museums Service, 1986, pp.62, 64, 108.