Fowler's Long Scale Calculator
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Fowler's Long Scale Calculator
- Type: Circular, pocketwatch type
- Size: 2-5/8 in / 7 cm
- Material: Nickel, glass, paper
- Scales: (equivalent scale notation)
- Front: constants D D6 D5 D4 D3 D2 D1
- Back: constants D DI L R2 R1 S T ST
- HvH: best match 1224
[Scale references on this page are for convenience of my readers and myself. The device doesn't use the traditional scale notation.]
Scales D1 through D6 make up the eponymous "long scale". Six concentric rings make up a single decade labelled 10 through 100. The manual suggests using the outermost D scale to obtain a low-precision result before using the long scale for the fine strokes.
The upper knob sets the obverse disk. The offset knob sets the black hairline on the obverse and the disk on the reverse. The red hairlines are fixed in place. There is no movable hairline on the reverse, but if the obverse index is set beneath the red hairline, the number under the black hairline is repeated on the reverse.
To multiply: Set index under red hairline (upper knob); set black hairline over multiplicand (offset knob); rotate disc so multiplier is beneath red hairline. Read product under black hairline. (See the reverse and discover your multiplicand, in case you forgot.) You can use either the long or short scales as long as you stick with the scales you started with.
With instructions and leather and felt case.
High-resolution manual scans (2 MB/page):
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