18th Century Maths

I’m a huge fan of old books. Textbooks are my favorites, but just about any old book will do. Even if it’s a lousy book, it will still make for a great decoration. So, when my dad called me up and told me he had a late-1700’s mathematics textbook for me, I got kind of excited (don’t judge me …). Thanks, dad!

The title page of the book gives a publication date of 1796 (MDCCXCVI, actually) for Thomas Dilworth’s The Schoolmaster’s Assistant, and the inside cover indicates that Jacob Libhart owned it in 1801. Despite its age, however, it’s in really good shape. The book starts off with some glowing reviews (some in verse) and a rather long intro by the author on educating youth: “Parents themſelves ſhould endeavour to be ſenſible of their Children’s Defects and Want of Parts; and not blame the Maſster for Neglect, when his greateſt Skill, with ſome, will produce but a ſmall Share of Improvement” (page X). Once you get through that, though, it gets into some great info. I had to adjust my reading to that pesky long ‘s’, but it’s been worth it.

Remember learning in school that there are three barley-corns to an inch? No?
How about the differences between Troy, Avoirdupois, and Apothecaries weights? Me neither …

It does contain a pretty nice collection of instructions for simple arithmetic, interest & rebates, present values of annuities, and working with “vulgar fractions.” He dedicates a lot more space to duodecimal calculations than I think anyone would ever have found useful and his explanations can be a bit abbreviated, but the story problems provide a great view of what might have been considered “everyday” problems at the time. There are even a few “pleasant and diverting” riddles; like this one:

A poor Woman carrying ſome Eggs to Market, met with a rude Fellow, who broke them all; but preſently after conſidering what he had done, went back and told the Woman he was willing to make Satisfaction, provided ſhe could tell how many there were; ſhe anſwered ſhe could not tell, but the beſt Account that ſhe could give, was, that when ſhe told them in by two at a Time there was one left, when by three, there was one left, and when by four, there was one left, but when ſhe told them in by five, there was none left; I demand how many Eggs the Woman had? (page 180)

So, we’re looking for a multiple of five that is one greater than a multiple of 2, 3, and 4. Like 25 (or 85, or 145, or …).  HOW MANY EGGS DID SHE HAVE!??

Yep … old books … very cool.