4.2 Years 1900-1909

Number of slide rules: 19.

The early K&E Mannheim slide rules began to compete with their European counterparts. Inverse, folded, and cubic scales began to become available as manufacturers appear to have experimented with a variety of standard scale arrangements this decade in search of more efficient computational power. See, for example, the Dietzgen rules with their special “B” scales (1762-B), as well as the inverse scales and “triplex” scale arrangements on the Kolesch slide rules. Specialty slide rules, for example for electrical calculations (“electros”) and for chemical proportions, and so on, came on the scene. The “log-log” scales, invented nearly a century earlier, are re-introduced on the early electro rules in Europe and by K&E on their duplex models at the end of this decade.

Some notable technical developments: Zeplin first flight; Wright Brothers and Kitty Hawk flights; Einstein’s development of special and general relativity; Ford’s Model T automobile.

Year	Maker	Model
1901	Scofield	Engineer’s Slide Rule
1901-1904	Kolesch	Mannheim
1902-1912	Dietzgen	1765
1903	Faber	350
1903	K&E	4054
1904	K&E	4041
1904-1905	Faber	367
c.1905	K&E	4035
c.1905	K&E	4041
1905-1907	Dietzgen	MultiplexProto
1905-1911	Kolesch	2574 Mannheim
1905-1911	Kolesch	2713 Stadia
1905-1911	Kolesch	2832 Triplex
c.1907	Dietzgen	1762-B
c.1907	Dietzgen	1762-B
1907	K&E	4013 Thacher
1909	Stanley London	Fuller’s Calculator Model No. 1
1909	The American Art Works	Slide Rule for Concrete Slabs
1909-1914	K&E	4056