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Date: 1934-1938

Inventory Number: 1990-1-0004a

Classification: Slide Rule

Subject:

Maker: Indeco (? - 1938)

Seller: Andrew J. Lloyd Company (fl. 1890 - 1930)

Cultural Region:

Place of Origin:

Dimensions:

slide rule: 0.6 × 15.3 × 2.4 cm (1/4 × 6 × 15/16 in.)

case: 0.8 × 16 × 3.5 cm (5/16 × 6 5/16 × 1 3/8 in.)

Accessories: brown leather case; instruction booklet (1990-1-0004b) on file

Description:

Rectangular celluloid rule with three slides in metal frame. The top and bottom slides are fixed; the center slide moves to left and right. A transparent yellow glass (?) runner with a vertical indicator line also moves to left and right, along grooves in the slide rule frame.

The slide rule is printed with four scales. Along the bottom edge of the top, fixed slide and the top edge of the center, moveable slide are, respectively, "A" and "B" scales. These are composed of two logarithmic scales (values 1 to 10) arranged side by side.

The bottom edge of the center, moveable slide and the top edge of the bottom, fixed slide are printed with logarithmic "C" and "D" scales, respectively, carrying values from 1 to 10.

The slide rule is stored in a brown leather case.

The surface of the runner is heavily scratched, and the metal frame is partially rusted.

The slide rule is printed with four scales. Along the bottom edge of the top, fixed slide and the top edge of the center, moveable slide are, respectively, "A" and "B" scales. These are composed of two logarithmic scales (values 1 to 10) arranged side by side.

The bottom edge of the center, moveable slide and the top edge of the bottom, fixed slide are printed with logarithmic "C" and "D" scales, respectively, carrying values from 1 to 10.

The slide rule is stored in a brown leather case.

The surface of the runner is heavily scratched, and the metal frame is partially rusted.

Signedface, center slide, center: INDECO RULE

Inscribedstamp on the bottom of the back of the instruction booklet: ANDREW J. LLOYD CO. / Harvard Square CAMBRIDGE.

FunctionUsed to solve multiplication and division problems, as well as squares and square roots.

To multiply, the user first moves the center slide to left or right such that the 1 on the C scale coincides with the value of the multiplier on the D 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 C scale. The coincident value on the D 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 D scale. He then moves the center slide to left or right such that the value of the divisor on the C scale falls under the hairline. Holding the slide in place, he locates the 1 on the C scale. The coincident value on the D scale is the quotient.

To find the square of a number, the user first moves the runner to left or right such that the hairline falls over the value on the D scale of the number to be squared. The coincident value on the A 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 A scale whose square root is to be taken. The coincident value on the D scale gives the square root.

To multiply, the user first moves the center slide to left or right such that the 1 on the C scale coincides with the value of the multiplier on the D 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 C scale. The coincident value on the D 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 D scale. He then moves the center slide to left or right such that the value of the divisor on the C scale falls under the hairline. Holding the slide in place, he locates the 1 on the C scale. The coincident value on the D scale is the quotient.

To find the square of a number, the user first moves the runner to left or right such that the hairline falls over the value on the D scale of the number to be squared. The coincident value on the A 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 A scale whose square root is to be taken. The coincident value on the D scale gives the square root.

Curatorial RemarksAn advertisement for an identical slide rule, priced at 50 cents, appears in the March 1934 edition of Popular Science. It is available in Google Books online by clicking here.

ProvenancePrivate donor, 1990.

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