c. 1861-1865, circular slide rule 'Palmers Computing Scale improved by Fuller', the reverse with separately rotating Fuller's Time Telegraph, by John E. Fuller New York, in embossed cloth-covered card case with 22 page booklet of instructions and information. The computing scale 28.8cm sq. Note: this early example uses two pages of the booklet, written in the course of the Civil War, to argue against the slave trade in terms of economic statistics, (utilising the 1860 census) as well as humanitarian principles. It concludes 'How long will it take 100 men with 63 slaves to guard to get the best of 400 men, who have no slaves, but a naval fleet, the Star Spangled Banner and a just cause with Liberty as a watchword? Officers of the Union army and navy will see this problem rightly solved for freedom's battle once begun though sometimes lost is always won'.