Fowler's long scale calculator
Fowler's long scale calculator
Obtained from the UK
This is my first circular 'slide' rule. Rather than sliding two scales along each other, this instrument has two dials used for computations. One dial is for accurate work and uses concentric rings where the other scale is for the various (rough) computations. The computations are done by rotating index lines on the dials. Unfortunately on the main side the glass is missing and thus the main (upright) index. However, this index is stationary allowing the instrument still to be used for demonstrations
One knob rotates only one index whereas the other rotates both an index on one side and the long scale dial on the other side allowing the transfer of values between the two scales. Really ingenious. Maybe more accurate than a regular slide rule but definitely more cumbersome to use (slower).
fowler calculator
8 other products in the same category:
Fowler's long scale calculator
Obtained from the UK