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Date: 1900-1940

Inventory Number: 1997-1-1926

Classification: Slide Rule

Subject:

User: William R. Osgood

Maker: A. W. Faber-Castell (1900-present)

Cultural Region:

Place of Origin:

City of Use:

Dimensions:

slide rule: 3.4 × 26 × 1.3 cm (1 5/16 × 10 1/4 × 1/2 in.)

leather case: 4.9 × 28.8 × 2.9 cm (1 15/16 × 11 5/16 × 1 1/8 in.)

Accessories: Brown leather case with flap closure, for storage

DescriptionRectangular wooden rule with three slides, faced with white celluloid. The top and bottom slides are fixed; the center slide is printed on both sides and moves to left and right. A glass runner with a vertical indicating line and a metal frame also moves to left and right.

The bottom edge of the top, fixed slide is printed with two logarithmic scales placed side by side, carrying (together) values from 1 to 100. The top edge of the bottom, fixed slide is printed with a single logarithmic scale, carrying values from 1 to 10.

The top edge of the face of the center, moveable slide is printed with a scale identical to that along the bottom edge of the top, fixed slide. The bottom edge of the face of the center slide is printed with a scale identical to that along the top edge of the bottom, fixed slide.

The back of the center, moveable slide is printed with three scales. The scale along the top edge of the slide, for "S", carries values from 35' to 90°. The center scale, "L", has values descending from 10 to 0. Printed along the bottom edge of the back of the slide is a "T" scale, with values ascending from 5.5 to 45.

The top edge of the slide rule is printed with a 10-inch scale. The bottom edge of the slide rule is printed with a 25-centimeter scale.

Printed underneath the moveable slide is a scale in centimeters, with values ranging from 26 to 51.

Printed on the back of the slide rule are tables for decimal equivalents of fractions, inches, and [pi], as well as unit conversion tables and the weights and ultimate strengths of various metals.

The bottom edge of the top, fixed slide is printed with two logarithmic scales placed side by side, carrying (together) values from 1 to 100. The top edge of the bottom, fixed slide is printed with a single logarithmic scale, carrying values from 1 to 10.

The top edge of the face of the center, moveable slide is printed with a scale identical to that along the bottom edge of the top, fixed slide. The bottom edge of the face of the center slide is printed with a scale identical to that along the top edge of the bottom, fixed slide.

The back of the center, moveable slide is printed with three scales. The scale along the top edge of the slide, for "S", carries values from 35' to 90°. The center scale, "L", has values descending from 10 to 0. Printed along the bottom edge of the back of the slide is a "T" scale, with values ascending from 5.5 to 45.

The top edge of the slide rule is printed with a 10-inch scale. The bottom edge of the slide rule is printed with a 25-centimeter scale.

Printed underneath the moveable slide is a scale in centimeters, with values ranging from 26 to 51.

Printed on the back of the slide rule are tables for decimal equivalents of fractions, inches, and [pi], as well as unit conversion tables and the weights and ultimate strengths of various metals.

Signedface, bottom slide, center: A. W. FABER MADE IN GERMANY DBGM 98350;

underneath moveable slide: 387 [trademark] FABER "CASTELL"

underneath moveable slide: 387 [trademark] FABER "CASTELL"

Inscribedback, right, bottom W.R.O.;

case, center: WM R OSGOOD;

stamped inside flap of case: 4041;

stamped inside flap of case, twice: William R. Osgood

case, center: WM R OSGOOD;

stamped inside flap of case: 4041;

stamped inside flap of case, twice: William R. Osgood

FunctionFor solving mathematics problems, including multiplication, division, squares, square roots, and trigonometric problems.

For problems involving square and square roots, the user may have the center slide in any position. To find the square of a number, he first moves the runner to left or right such that the hairline falls over the value on the bottom slide's scale of the number to be squared. The coincident value on the top slide's scale gives the square. To find the square root of a number, the user first moves the runner to left or right such that the hairline falls over the value on the top slide's scale whose square root is to be taken. The coincident value on the bottom slide's scale gives the square root.

For multiplication and division problems, the user uses the face of the reversible slide. To multiply, he first moves the center slide to left or right such that the 1 on the center slide's bottom scale scale coincides with the value of the multiplier on the bottom slide's scale. Then, holding the slide in place, he moves the runner to left or right until the hairline is on top of the value of the multiplicand on the center slide's bottom scale. The coincident value on the bottom slide's scale is the product.

To divide, the user first moves the runner to left or right such that the hairline is on top of the value of the dividend on the bottom slide's scale. He then moves the center slide to left or right such that the value of the divisor on the center slide's bottom scale falls under the hairline. Holding the slide in place, he locates the 1 on the center slide's bottom scale. The coincident value on the bottom slide's scale is the quotient.

For problems involving square and square roots, the user may have the center slide in any position. To find the square of a number, he first moves the runner to left or right such that the hairline falls over the value on the bottom slide's scale of the number to be squared. The coincident value on the top slide's scale gives the square. To find the square root of a number, the user first moves the runner to left or right such that the hairline falls over the value on the top slide's scale whose square root is to be taken. The coincident value on the bottom slide's scale gives the square root.

For multiplication and division problems, the user uses the face of the reversible slide. To multiply, he first moves the center slide to left or right such that the 1 on the center slide's bottom scale scale coincides with the value of the multiplier on the bottom slide's scale. Then, holding the slide in place, he moves the runner to left or right until the hairline is on top of the value of the multiplicand on the center slide's bottom scale. The coincident value on the bottom slide's scale is the product.

To divide, the user first moves the runner to left or right such that the hairline is on top of the value of the dividend on the bottom slide's scale. He then moves the center slide to left or right such that the value of the divisor on the center slide's bottom scale falls under the hairline. Holding the slide in place, he locates the 1 on the center slide's bottom scale. The coincident value on the bottom slide's scale is the quotient.

Primary SourcesPickworth, Charles N. "Instructions for the use of A. W. Faber's Improved Calculating Rule." New York: A. W. Faber, c. 1900. Several pages are available online here.

ProvenanceOwned by William R. Osgood (Engineer, Harvard 1917); donated by his nephew on November 20, 1997.

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