4.14 Thornton, UK

Alexander George Thornton founded his company in 1880 in Manchester, England, and the firm grew to become one of the largest manufacturers of drawing instruments and slide rules in Britain. The Precision Instrument Co was taken over in 1901 and PIC continued to be used by Thornton as a trade mark until about 1970. The firm officially became British Thornton in 1967 and merged with ESF at Burley in 1992. A distinguishing feature of many Thornton slide rules is their use of “differential” scales for determining values of trigonometric functions. (See the vignette British Thornton Special Scales.)

Thornton Collection

Total number of Thornton slide rules in the collection: 3. \(~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\)

Model Year Serial Typ Mat Size Case Note
P.I.C. 101 1945 L wd 10 yes Log-log rule, mahogany; date code 45; green PIC case; gold metal cursor; owner H. Clabaugh, Oxford, ’45
P.I.C. F3649 1954 L wd 10 yes Log-log rule, mahogany; date code 54 8; green PIC case; 3-hairline cursor
P221
1967 L pl 10 yes British Thornton P221 Comprehensive; Ps, Pt, Td/Sd scales