1851 Great Exhibition: Official Catalogue: Class X.: William Ackland
368. ACKLAND, WILLIAM, 19 Dorset Street, Portman square — Inventor.
Machine for the graduation of hydrometers, thermometers, etc. Scale for an hydrometer, showing specific gravities. Another showing per centages., according to Tralles.
Hydrometer in a finished state, showing Twaddell's scale.
In hydrometers showing specific gravities and per centages the divisions are of unequal magnitude. By this machine, the subdivisions are placed so that each shall be in its true mathematical position; it is applicable to the subdivisions on the scales of thermometers, barometers, verniers, the lines of sines, secants, tangents, semi-tangents, chords, logarithmic numbers, and, indeed, to all straight scales requiring equal or unequal divisions.
A brass hydrometer for showing specific gravities.
[An hydrometer is an instrument originally designed for the purpose of measuring the gravity, density, etc., of water; but the knowledge of the specific gravities of bodies, both fluid and solid, is so essential, that there have been many contrivances for their determination.—J. G.]