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Stephens' "Supremathic" |
The maker’s advertising proclaims: “Supremathic has absolutely nothing in common with all the circular slide rules known up to this day”. True indeed... |
The Supremathic’s front side, which is used for multiplication and division, has three elements: The body, some 10 cm square, with two stationary paper scales whose numbers are engraved in the metal; the cursor, a transparent disc with a red hairline and a flattish knob to turn it; and a metal wheel with a knurled edge that shows through a window at the top, and bears another paper scale. The back side has 5 scales (glued to the back of the wheel) showing through windows in the body. All this can be difficult to grasp without holding the device in your hand; try this annotated photo and the two below for more insight. |
Click a photo to enlarge |
To multiply, say, 6 by 5 you go through a sequence of motions. First, you set the wheel to 6 and bring the cursor to its zero position (photo at left below). Then you rotate the wheel counterclockwise until the hairline on the cursor, which is swept along with the wheel, points to 5 on the multiplication scale (photo at right); the result (3.0, i.e. 30) can now be read on the wheel under the hairline of the top window. This system has the advantage that the results always appear at the same location on the instrument, in this top window. |
Click a photo to enlarge |
Division uses another scale in a similar procedure; Trig and Log functions use the scales at the back, with the result read at the usual place on the front. |
Exhibit provenance: EBay.
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