Thacher's calculating instrument
Date: circa 1932
Inventory Number: 1992-1-0004
Classification: Slide Rule
Subject:
Maker: Keuffel & Esser Company (1867 - 1987)
Inventor: Edwin Thacher (1839 - 1920)
Cultural Region:
Place of Origin:
Dimensions:
slide rule: 14.5 × 57.5 × 13 cm (5 11/16 × 22 5/8 × 5 1/8 in.)
case: 16.5 × 60.5 × 16.8 cm (6 1/2 × 23 13/16 × 6 5/8 in.)
Accessories: instruction booklets (2), information sheet; box
DescriptionThis instrument consists of a cylindrical slide provided with a wooden knob at each end. This cylinder can both rotate and move horizontally within an open enveloppe of equidistant bars of triangular section (twenty in all, numbered 1 to 20). The latter are connected to brass rings at each end, attached to a wooden base. Upon the slide are wrapped two complete logarithmic scales, one on each side of the center. Each scale from 100 to 1000 is divided into forty parts of equal length. The figures and divisions on the scales are made to face both ways, that they may be read from either edge of the bars. The bars has two other sets of scales, which are used in conjunction with the ones on the cylinder.
The scales on the sliding cylinder are known as "A". The scales on the lower part of the triangular bars (closer to the cylinder) are known as "B". The scales on the higher part of the bars are known as "C".
When not in use, the instrument is stored in a wooden box. Inside were booklets (one is now in the CHSI Library, instrument's file) and an information sheet. A trade card is glued on the inside cover of the box.
The scales on the sliding cylinder are known as "A". The scales on the lower part of the triangular bars (closer to the cylinder) are known as "B". The scales on the higher part of the bars are known as "C".
When not in use, the instrument is stored in a wooden box. Inside were booklets (one is now in the CHSI Library, instrument's file) and an information sheet. A trade card is glued on the inside cover of the box.
In Collection(s)
Signedon base, stamped: KEUFFEL & ESSER CO.
on ivory plate and trade card, inside box cover: KEUFFEL & ESSER CO.
on cylinder: Made by Keuffel & Esser Co. N.Y.
on cylinder: Patented by Edwin Thatcher [sic], C.E. Nov. 1'st 1881.
on ivory plate and trade card, inside box cover: KEUFFEL & ESSER CO.
on cylinder: Made by Keuffel & Esser Co. N.Y.
on cylinder: Patented by Edwin Thatcher [sic], C.E. Nov. 1'st 1881.
FunctionExcerpt from the instruction manual: "By the use of this instrument the drudgery of calculation is avoided, and the relief to the mind may be compared with the most improved mechanical appliances in overcoming the wear and tear of manual labor." [...]
"By use of this instrument results are more reliable than when brought out in the usual way; mistakes are less liable to occur, and if they should occur the whole work can be quickly checked. The only liability to error is in the misreading of the figures and divisions upon the scales, which are essentially the same as the reading of the inches and parts of a carpenter's rule." [...]
"The bridge engineer will find it useful in finding the moments and shears in plate girders, the strains and sections in trusses, the bearing an shearing values of pins and rivets, the thickness of bearing plates, the length of tie plates, and estimates of quantities, costs, etc. ... The railway engineer will find it useful in the mensuration of lines, areas, and solids... The mechanical engineer will find it useful ... in finding the pitch, number of teeth, and diameter of toothed wheels... The hydraulic engineer will find it useful in ascertaining the force, velocity, and pressure of water... The architect and actuary, not less than the engineer, will find it useful in their various calculations and estimates."
"By use of this instrument results are more reliable than when brought out in the usual way; mistakes are less liable to occur, and if they should occur the whole work can be quickly checked. The only liability to error is in the misreading of the figures and divisions upon the scales, which are essentially the same as the reading of the inches and parts of a carpenter's rule." [...]
"The bridge engineer will find it useful in finding the moments and shears in plate girders, the strains and sections in trusses, the bearing an shearing values of pins and rivets, the thickness of bearing plates, the length of tie plates, and estimates of quantities, costs, etc. ... The railway engineer will find it useful in the mensuration of lines, areas, and solids... The mechanical engineer will find it useful ... in finding the pitch, number of teeth, and diameter of toothed wheels... The hydraulic engineer will find it useful in ascertaining the force, velocity, and pressure of water... The architect and actuary, not less than the engineer, will find it useful in their various calculations and estimates."
Curatorial RemarksPatented by Thacher in 1881, the original scale divisions are dated from 1882, and were done by the London based W. F. Stanley. Keuffel & Esser Co. took over the production of this slide rule in 1897. It is interesting to note that Stanley misspelled Thacher's name (Thatcher) on the original engraving, and K&E never bothered to correct the mistake in the following decades.
For more information on this type of slide rule, including the above information and the patent's text, take a look at the following website.
For more information on this type of slide rule, including the above information and the patent's text, take a look at the following website.
Primary SourcesKeuffel & Esser Co., Directions for Using Thacher's Calculating Instrument (New York: Keuffel & Esser Co., ca 1932).
