1851 Great Exhibition: Official Catalogue: Class X.: John and Alfred Rooker
340. BOOKER, JOHN and ALFRED, 26 East Street, Foundling — Manufacturers.
Sliding rule of involution, presenting at one view the series of powers arising from the successive multiplication of whole or fractional numbers. Questions relating to the increase of population, to the calculation of probabilities, to compound interest, etc., are resolvable by this instrument.
Specimen of hand dividing.