in case you were wondering...

this is the first of several journeys the archive will make into ropp's calculator for the pocket, published in 1912, and rescued from obscurity a few sundays ago at the long beach flea market.

you'll have to click on the image to be able to read it, but it's a beautiful chart of "the specific gravity of well known substances" (including aluminum, gum arabic, castor oil and human blood).

ropp's little book features an insane amount of information including "time and labor saving tables, also the rules, principles, and short cuts for arithmatic, mechanics, and mensuration; concisely and clearly stated for practical use, handy review, and ready reference for the use of farmers, mechanics, business men, bankers, miners, laborers, and dealers in grain, stock, cotton, hay, feed, coal, lumber, etc."