Ivory Slide Rule by Huddy Two foot Four Fold Engineer's Routledge Type Ruler

A New Type of Slide Rule Discovered. Two types of early 19th century engineers slide rules were produced with Routledge logarithmic scales:
A. 12 inch long slide rules (2 foot 2 fold) which were too long for engineers to carry.
B. 6 inch long slide rules (2 foot 4 fold) which were short but inaccurate.
We show here a third type that is short and accurate. This is an ivory slide rule, 6 inch long when folded, invented by F. Huddy who worked in London, between 1842 and 1856. The upper part of each of the outer faces of the rule contains a slider, 4 logarithmic scales and tables. Each slider is held between two grooves to enable free lateral movement. The scales marked A, B and C, have two-decade logarithmic scales that run from 1 to 100. D scale has one log cycle from 1 to 10 for use in calculating squares and square roots. The labeling A, B, C and D became the standard on later rules. All fittings and slides were made with German silver. All hinges were crafted with Iron and German silver alternately to ease friction. The Lower part of the rule contains tables of engineering importance, such as conversion of cubic foot to cubic inch, imperial gallon to cubic inch, area of polygons with n sides etc. On the inner face, the rule has scales of inches (1'-24') and also of ¾, ½ and ¼ inches. On upper and lower edges there are scales of decimals of an inch and foot to facilitate the use of the rule for decimal fractions.
Francis Huddy was a Mathematical Instrument Maker who flourished in England between 1824 and 1858. He worked in 37 Duke Street, Smithfield between 1842 and 1856 and in Red Lion Street, Holborn, between1856 and 1858, both in London. This ivory slide rule with Routledge scales is in very good condition, museum quality without rust or chips. It was hand made for Mr. H.I.F. Morgan from Rotherhithe, London, probably a wealthy engineer.