Measuring & Mapping

Where, how far, and how much? People have invented an astonishing array of devices to answer seemingly simple questions like these. Measuring and mapping objects in the Museum's collections include the instruments of the famous—Thomas Jefferson's thermometer and a pocket compass used by Meriwether Lewis and William Clark on their expedition across the American West. A timing device was part of the pioneering motion studies of Eadweard Muybridge in the late 1800s. Time measurement is represented in clocks from simple sundials to precise chronometers for mapping, surveying, and finding longitude. Everyday objects tell part of the story, too, from tape measures and electrical meters to more than 300 scales to measure food and drink. Maps of many kinds fill out the collections, from railroad surveys to star charts.

This instrument consists of two mercury-in-glass thermometers mounted on an aluminum frame that is marked "H. J. GREEN B'KLYN N.Y." and "No. 147 SIGNAL CORPS. U.S. ARMY" and equipped with a wooden handle.
Description
This instrument consists of two mercury-in-glass thermometers mounted on an aluminum frame that is marked "H. J. GREEN B'KLYN N.Y." and "No. 147 SIGNAL CORPS. U.S. ARMY" and equipped with a wooden handle. Each thermometer has a milk white back and a clear front that is graduated every degree Fahrenheit. On one the scale runs from -40 to +137; on the other, it runs from -38 to +122. This was made between 1890 (when Green moved his business to Brooklyn) and 1923 (when the instrument came to the Smithsonian).
Ref: Henry J. Green, (Brooklyn, about 1890), p.31.
Location
Currently not on view
date made
1890-1923
maker
H. J. Green
ID Number
PH.308200.2
accession number
70852
catalog number
308200.2
This is a short-stem instrument designed for industrial use. The brass V-shaped case is marked “Tycos” at top, and “Taylor / Instrument / Co.” at bottom.
Description
This is a short-stem instrument designed for industrial use. The brass V-shaped case is marked “Tycos” at top, and “Taylor / Instrument / Co.” at bottom. The black housing around the mercury-in-glass thermometer with a milk glass tube has a scale from 32 to 240 degrees Fahrenheit, and is marked “Tycos / ROCHESTER / N.Y. U.S.A.”
Hohmann & Maurer had been making instruments of this sort since the mid-1880s, and continued doing so after being bought out by Taylor Bros. in 1896. This example was made after 1908 when the Taylor Instrument Co. introduced the Tycos trade mark and dropped the Hohmann & Maurer signature and trade mark. It came to the Smithsonian in 1923.
Location
Currently not on view
date made
ca 1923
maker
Taylor Instrument Co.
ID Number
PH.308162
catalog number
308162
accession number
70532
In 1913 Leonard Hill, a British physiologist interested in the relationship between atmosphere and health, described a Kata thermometer (Hill’s term) that represented the humidity in terms of the time it took for the enclosed liquid to fall a certain amount.
Description
In 1913 Leonard Hill, a British physiologist interested in the relationship between atmosphere and health, described a Kata thermometer (Hill’s term) that represented the humidity in terms of the time it took for the enclosed liquid to fall a certain amount. This example is an alcohol-in-glass thermometer with a large cylindrical bulb and enlargements at the lower and upper ends of the stem. The alcohol is violet-colored (mostly faded to orange). The milk-white back of the stem is marked “J. Hicks 8 9 & 10 Hatton Garden London No 261 F531.” The front is marked “Fahrt” and has a scale reading from 100 to 95 degrees Fahrenheit, in tenths.
Ref.: Leonard Hill, et. al., “The Influence of the Atmosphere on our Health and Comfort in Confined and Crowded Places,” Smithsonian Miscellaneous Collections 60 (1913), #23.
Location
Currently not on view
date made
1913-1920
maker
J. J. Hicks
ID Number
PH.317457
catalog number
317457
accession number
230396
A hydgrograph records humidity as it varies over time. This example, which came to the Smithsonian in 1923, is marked "JULIEN P. FRIEZ & SONS, BELFORT METEOROLOGICAL OBSERVATORY, 1230 E.
Description
A hydgrograph records humidity as it varies over time. This example, which came to the Smithsonian in 1923, is marked "JULIEN P. FRIEZ & SONS, BELFORT METEOROLOGICAL OBSERVATORY, 1230 E. BALTIMORE STREET, BALTIMORE, M.D., U.S.A." and "HYGROGRAPH, Type ML 16, SERIAL 74865, SIGNAL CORPS, U.S. ARMY, ORDER 110418 DATE 2.8.23." The firm began trading under this name in 1914.
Location
Currently not on view
date made
1914-1923
maker
Friez, Julien P.
Julien P. Friez & Sons
ID Number
PH.308178.1
accession number
70852
catalog number
308178.1
This is the Pathfinder, an inexpensive watch model made by E. Ingraham and Company, Bristol, Conn. These “dollar watches” made by Ingraham and other firms were easier to make than high-grade watches and very much in demand.
Description
This is the Pathfinder, an inexpensive watch model made by E. Ingraham and Company, Bristol, Conn. These “dollar watches” made by Ingraham and other firms were easier to make than high-grade watches and very much in demand. They got their nickname in 1896 when such timekeepers began to sell for about $1. In contrast, the best pocket watches from other American watchmaking firms at the time could cost over $150. Because they were inexpensive, “dollar watches” were often giveaways during promotions for other products or marketed for children.
Location
Currently not on view
date made
1920
manufacturer
E. Ingraham Company
ID Number
1984.0416.169
catalog number
1984.0416.169
accession number
1984.0416
This mechanical alarm clock features a radium dial to glow in the dark. Made about 1920 by the Waterbury Clock Co., the model is called the Turnout.Currently not on view
Description
This mechanical alarm clock features a radium dial to glow in the dark. Made about 1920 by the Waterbury Clock Co., the model is called the Turnout.
Location
Currently not on view
date made
1918-1920
manufacturer
Waterbury Clock Company
ID Number
1986.0434.04
catalog number
1986.0434.04
accession number
1986.0434
catalog number
1986.434.04
The face of this cylindrical instrument is marked “BAROMETRE HOLOSTERIQUE / COMPENSÉ / NAUDET & CIE.
Description
The face of this cylindrical instrument is marked “BAROMETRE HOLOSTERIQUE / COMPENSÉ / NAUDET & CIE. / PARIS / SERVICE MÉTÉOROLOGIQUE.” The additional circle with the letters “HBPN” was the logo of Naudet & Cie., and probably represents the words: Holosteric Barometer Paul Naudet. The firm was founded in Paris in 1860 by Paul Naudet, and used the term Holosteric to mean “without liquid.” The scale around the edge of the silvered metallic dial extends from 65 to 80 millimeters of mercury and is graduated to tenths. A blued needle indicates the present pressure; a brass needle indicates a previous observation. The U.S. Signal Corps transferred this instrument to the Smithsonian in 1923.
Location
Currently not on view
date made
1860-1923
maker
Naudet & Cie.
ID Number
PH.308186
accession number
70852
catalog number
308186
This is a hefty instrument, 5 inches in diameter and 2 inches deep. The face reads: “Surveying Aneroid / COMPENSATED FOR TEMPERATURE / Short & Mason / London / Tycos / Made in England.” The altitude scale around the circumference of the face reads in from sea level to 6000 feet.
Description
This is a hefty instrument, 5 inches in diameter and 2 inches deep. The face reads: “Surveying Aneroid / COMPENSATED FOR TEMPERATURE / Short & Mason / London / Tycos / Made in England.” The altitude scale around the circumference of the face reads in from sea level to 6000 feet. An inner pressure scale reads from 24.8 to 31 inches of mercury. Both scales can be read by a magnifying lens.
The Taylor Instrument Companies began operating, as such, 1904, introduced the Tycos trade mark in 1908, and gave this instrument to the Smithsonian in 1923.
Location
Currently not on view
date made
ca 1920
maker
Short & Mason
ID Number
PH.308172
catalog number
308172
accession number
70532
Torsion balances are used to measure weak natural forces. Torsion balances generally consist of a straight rod with masses attached to each end, suspended from a wire. It is then encased in metal to isolate it from temperature or wind disturbance.
Description
Torsion balances are used to measure weak natural forces. Torsion balances generally consist of a straight rod with masses attached to each end, suspended from a wire. It is then encased in metal to isolate it from temperature or wind disturbance. All mass near or far has an influence on the rod, but the wire resists this force and twists in the opposite direction, producing through its twisting the measurements of the forces imposed upon it.
The Humble Oil and Refining Co. purchased this photographic torsion balance in 1926—this was just four years after Americans began making gravimetric surveys for prospecting purposes—and used it for oil exploration in Texas, New Mexico, Louisiana, Mississippi, and Alabama until the introduction of gravimeters in 1936. Although this instrument has no signature, it was probably made by Askania, in Friedenau, Germany. Askania opened a sales office in Houston, Texas in the 1920s.
The Schweydar Bamberg instrument is an Eötvös torsion balance with a photographic arrangement for recording the results automatically. The form was described in 1921 by Wilhelm Schweydar, a German geophysicist, and produced by Carl Bamberg. It was publicized in the United States by C. A. Heiland, a German geophysicist who worked for Askania in Houston and who taught at the Colorado School of Mines.
Ref: Askania Bulletin Geo 103E
W. Schweydar, "Die Photographische registrierende Eötvössche Torsionswage der Firma Carl Bamberg in Berlin-Friedenau," Zeitschrift fur Instrumentendekunde 41 (1921): 175-183.
C. A. Heiland, "Schweydar-Bamberg Types of Eötvös Torsion Balance" Bulletin of the American Association of Petroleum Geologists 10 (1926): 1201-1209.
C. A. Heiland, Directions for the Use of the Askania Torsion Balance (Houston, 1933).
date made
1926
maker
Askania
ID Number
AG.MHI-P-7680
catalog number
MHI-P-7680
accession number
230370
The "Universal Theodolite" that Heinrich Wild introduced in 1923, later known as the T2, incorporated a radically new design. It was also highly successful—about 100,000 of these instruments were eventually produced. This example is marked "Heinrich Wild Heerbrugg No.
Description
The "Universal Theodolite" that Heinrich Wild introduced in 1923, later known as the T2, incorporated a radically new design. It was also highly successful—about 100,000 of these instruments were eventually produced. This example is marked "Heinrich Wild Heerbrugg No. 218." Wild Heerbrugg, Inc. gave it to the Smithsonian in 1961, stating that it had had been delivered on April 12, 1924, and used until July 1960 in the Swiss Canton of Tessin. The serial number probably means that this is the 18th instrument of this sort made for the market.
This Wild theodolite has a steel frame, and weighs only 9.5 pounds. The horizontal and vertical circles are glass, and read directly to single seconds. The telescope magnifies 24 times and, equipped with stadia wires, it can be used for tachymetry. An auxiliary eyepiece lying alongside the telescope allows the user to read either circle without moving away from the station. By a combination of internal optics, each reading gives the mean of two opposite points on the circles.
Ref: Henry Wild's Universal Theodolite (Heerbrugg, about 1925).
Location
Currently not on view
date made
1924
maker
Wild
ID Number
PH.319023
catalog number
319023
accession number
231959
Irving Langmuir received a Ph.D. in physical chemistry in 1906 from the University of Göttingen. He studied under Walther Nernst, who had invented a new type of incandescent lamp only a few years before.
Description
Irving Langmuir received a Ph.D. in physical chemistry in 1906 from the University of Göttingen. He studied under Walther Nernst, who had invented a new type of incandescent lamp only a few years before. In 1909 Langmuir accepted a position at the General Electric Research Laboratory in Schenectady, New York. Ironically, he soon invented a lamp that made Nernst's lamp (and others) obsolete.
Langmuir experimented with the bendable tungsten wire developed by his colleague William Coolidge. He wanted to find a way to keep tungsten lamps from "blackening" or growing dim as the inside of the bulb became coated with tungsten evaporated from the filament. Though he did not solve this problem, he did create a coiled-tungsten filament mounted in a gas-filled lamp—a design still used today.
Up to that time all the air and other gasses were removed from lamps so the filaments could operate in a vacuum. Langmuir found that by putting nitrogen into a lamp, he could slow the evaporation of tungsten from the filament. He then found that thin filaments radiated heat faster than thick filaments, but the same thin filament–wound into a coil–radiated heat as if it were a solid rod the diameter of the coil. By 1913 Langmuir had gas–filled lamps that gave 12 to 20 lumens per watt (lpw), while Coolidge's vacuum lamps gave about 10 lpw.
During the 1910s GE began phasing-in Langmuir's third generation tungsten lamps, calling them "Mazda C" lamps. Although today's lamps are different in detail (for example, argon is used rather than nitrogen), the basic concept is still the same. The lamp seen here was sent to the National Bureau of Standards in the mid 1920s for use as a standard lamp.
Lamp characteristics: Brass medium-screw base with skirt and glass insulator. Two tungsten filaments (both are C9 configuration, mounted in parallel) with 6 support hooks and a support attaching each lead to the stem. The stem assembly includes welded connectors, angled-dumet leads, and a mica heat-shield attached to the leads above the press. The shield clips are welded to the press. Lamp is filled with nitrogen gas. Tipless, G-shaped envelope with neck.
Date made
ca 1925
date made
ca. 1925
ID Number
1992.0342.23
accession number
1992.0342
catalog number
1992.0342.23
The U.S. Coast & Geodetic Survey acquired this compass in 1922 and transferred it to the Smithsonian in 1929. Its needle consists of four parallel strips of steel enclosed in a brass ring. The inscription reads "U.S.C.&G.S. No. 18."Currently not on view
Description
The U.S. Coast & Geodetic Survey acquired this compass in 1922 and transferred it to the Smithsonian in 1929. Its needle consists of four parallel strips of steel enclosed in a brass ring. The inscription reads "U.S.C.&G.S. No. 18."
Location
Currently not on view
date made
1920s
ID Number
PH.309671
catalog number
309671
accession number
106954
An advertising novelty for the Hotel Kankakee of Kankakee, Ill. This six-inch ruler is made of celluloid and has a 1929 calendar printed on the reverse. The front has advertising copy stating "All Outside Rooms Fireproof" and "Wonderful Dining Room."Currently not on view
Description (Brief)
An advertising novelty for the Hotel Kankakee of Kankakee, Ill. This six-inch ruler is made of celluloid and has a 1929 calendar printed on the reverse. The front has advertising copy stating "All Outside Rooms Fireproof" and "Wonderful Dining Room."
Location
Currently not on view
date made
1929
maker
American Art Works, Inc.
ID Number
2006.0098.1045
accession number
2006.0098
catalog number
2006.0098.1045
This mercury-in-glass thermometer with a milk-white back is held in a flat black housing. The scale reads from 20 to 230 degrees Fahrenheit, with an indication for “WATER/BOILS.” It was probably made by Hohmann & Maurer. It came to the Smithsonian in 1923.Currently not on view
Description
This mercury-in-glass thermometer with a milk-white back is held in a flat black housing. The scale reads from 20 to 230 degrees Fahrenheit, with an indication for “WATER/BOILS.” It was probably made by Hohmann & Maurer. It came to the Smithsonian in 1923.
Location
Currently not on view
date made
1885-1923
ID Number
PH.308158
catalog number
308158
accession number
70532
Grand is one of four boats used to survey the "ruggedest" 300 miles of the Colorado River's Grand Canyon during the 1923 expedition by the U.S. Geological Survey. Led by Col.
Description
Grand is one of four boats used to survey the "ruggedest" 300 miles of the Colorado River's Grand Canyon during the 1923 expedition by the U.S. Geological Survey. Led by Col. Claude Birdseye, the expedition's primary purpose was to survey potential dam sites for the development of hydroelectric power. Indeed, the survey party mapped twenty-one new sites.
Grand is eighteen feet long, with a beam of four feet, eleven inches. Heavily built of oak, spruce, and cedar, the boat weighs about 900 pounds. Grand is one of three boats ordered in 1921 by the survey's sponsors, the Edison Electric Company, and built at the Fellows and Stewart Shipbuilding Works in San Pedro. The vessels were patterned after those designed by the Kolb brothers, who had based their boats on vessels used by trappers in the upper Colorado River canyons.
Location
Currently not on view
date made
1921
associated date
1923
associated institution
US Geological Survey
maker
Fellows and Stewart Shipbuilding Works
ID Number
TR.034381
catalog number
034381
34381
accession number
71541
This mechanical alarm clock was made about 1925 by the William Gilbert Clock Co., Winsted, Conn. The model, suggesting an aggressive wakeup, is called the Tornado.Currently not on view
Description
This mechanical alarm clock was made about 1925 by the William Gilbert Clock Co., Winsted, Conn. The model, suggesting an aggressive wakeup, is called the Tornado.
Location
Currently not on view
date made
ca 1925
manufacturer
William Gilbert Clock Co.
ID Number
1984.0416.577
catalog number
1984.0416.577
accession number
1984.0416
C. L. Berger and Sons in Boston designed this instrument for use in cities and in bridge and tunnel construction. This example, serial number 14244, was made in 1923 and used by the Clayton Engineering Company in Clayton, Missouri.Currently not on view
Description
C. L. Berger and Sons in Boston designed this instrument for use in cities and in bridge and tunnel construction. This example, serial number 14244, was made in 1923 and used by the Clayton Engineering Company in Clayton, Missouri.
Location
Currently not on view
date made
1923
maker
C. L. Berger and Sons
ID Number
2009.0079.01
catalog number
2009.0079.01
accession number
2009.0079
The Rude Star Finder lets a navigator identify a star from its altitude above the horizon. It consists of planispheric maps of the northern and southern skies, the rims of which are graduated to two minutes of time.
Description
The Rude Star Finder lets a navigator identify a star from its altitude above the horizon. It consists of planispheric maps of the northern and southern skies, the rims of which are graduated to two minutes of time. Each planisphere has a celluloid meridian arm for determining the declination of stars, with a slide that can be adjusted for the latitude of the observer. There are in addition eleven transparent celluloid altitude-azimuth templates for use at different latitudes up to 66° north and south–that is, over the greater part of the navigable waters of the globe; a set of pins for marking the positions of the planets; an instruction brochure; and a cardboard case. The instrument bears the inscription "THE MARINER'S PRACTICAL STAR FINDER / A SIMPLE MEANS FOR IDENTIFYING AND SPOTTING STARS AND PLANETS / ... / G. T. RUDE Hydrographic and Geodetic Engineer / U.S. Coast and Geodetic Survey / Patents applied for / Price $12.00"
Gilbert Rude applied for a patent in December 1920. This example was made before the patent issued in December 1921. Rude donated it to the Smithsonian in 1957.
Location
Currently not on view
date made
1921
maker
Rude, Gilbert T.
ID Number
PH.315070
catalog number
315070
accession number
214892
This is a brass instrument, 5¼ inches diameter and 2½ inches deep.
Description
This is a brass instrument, 5¼ inches diameter and 2½ inches deep. The inscriptions on the metal face read “Stormoguide” and “COMPENSATED FOR TEMPERATURE” and “Tycos” and “UNITED STATES COPYRIGHT 1922 TAYLOR INSTRUMENT COMPANIES, ROCHESTER, N.Y.” The pressure scale around the circumference reads from 27.5 to 31.5 inches of mercury, in fifths of an inch. Letters around the scale, running from A to K, correlate with various weather conditions.
An altitude scale on the back of the instrument extends from 0 to 3500 feet, and reads: “ROTATE THIS PLATE UNTIL THE ARROW ON THE CASE POINTS TO THE ALTITUDE OF YOUR LOCALITY PATENTED AUGUST 18-1914”
The Stormoguide was based on a design developed by Francis E. Collinson of London, England. It was widely promoted for domestic and amateur use.
The Taylor Instrument Companies began operating, as such, 1904, and introduced the Tycos trade mark in 1908. It obtained a copyright on the term Stormoguide in 1922, and advertised it as a simplified barometer that indicated weather probabilities for 12 to 24 hours in advance. It gave this example to the Smithsonian in 1923.
Ref: Francis E. Collinson, “Barometer,” U.S. Patent 1,107,496 (1914).
Location
Currently not on view
date made
1922
ID Number
PH.308170
catalog number
308170
accession number
70532
Albert Ott was a precision instrument maker who began in business in Kempton, a small town in Bavaria, in 1880, and was later joined by his sons, Herman and Ludwig. Over the years, the Otts collaborated with many distinguished European hydraulic engineers.
Description
Albert Ott was a precision instrument maker who began in business in Kempton, a small town in Bavaria, in 1880, and was later joined by his sons, Herman and Ludwig. Over the years, the Otts collaborated with many distinguished European hydraulic engineers. This example, which dates from around 1917, is marked with the Ott monogram. The additional “Keuffel & Essser, Co., New York, No. 2237” signature refers to the firm that imported these instruments into the United States. The National Bureau of Standards, the organization that calibrated current meters for federal agencies and engineers in private practice, transferred it to the Smithsonian in 1959.
Ref: Horace Williams King, Handbook of Hydraulics for the Solution of Hydrostatic and Fluid-Flow Problems (New York, 1918), p. 236.
Arthur H. Frazier, Water Current Meters in the Smithsonian Collections of the National Museum of History and Technology (Washington, D.C., 1974), pp. 68-71.
Location
Currently not on view
date made
ca 1920
dealer
Keuffel & Esser Co.
maker
Ott, Albert
ID Number
PH.316593
accession number
225869
catalog number
316593
Lucien Vidie was a Frenchman who made the first satisfactory metallic barometer in 1843, and obtained his first patents in 1844. For the mechanism he used a corrugated diaphragm supported by 33 helical springs encased in a strong evacuated metal box.
Description
Lucien Vidie was a Frenchman who made the first satisfactory metallic barometer in 1843, and obtained his first patents in 1844. For the mechanism he used a corrugated diaphragm supported by 33 helical springs encased in a strong evacuated metal box. This example is of that form, but probably not of Vidie’s manufacture. The face is marked “BARÓMETRO ANEROIDE” as well as “TEMPESTAD,” “LLÚVIA Ó VIENTO,” “VARIABLE,” “BUEN TIEMP,” and “CONSTANTE.” The scale extends from 17.5 to 31.5 inches of mercury, and from 68 to 80 cm of mercury. The Taylor Instrument Companies donated it to the Smithsonian in 1923.
Ref.: W.E.K. Middleton, (Baltimore, 1964), pp. 400-406.
Location
Currently not on view
date made
1845-1923
ID Number
PH.308166
catalog number
308166
accession number
70532
This instrument consists of two mercury-in-glass thermometers mounted on an aluminum frame that is marked "H. J. GREEN B'KLYN N.Y." and "No. 117 SIGNAL CORPS. U.S. ARMY" and equipped with a wooden handle.
Description
This instrument consists of two mercury-in-glass thermometers mounted on an aluminum frame that is marked "H. J. GREEN B'KLYN N.Y." and "No. 117 SIGNAL CORPS. U.S. ARMY" and equipped with a wooden handle. Each thermometer has a milk-white back and a clear front that is graduated every degree Fahrenheit. On one the scale runs from -37 to +127; on the other it runs from -32 to +128. It was made between 1890 (when Green moved his business to Brooklyn) and 1923 (when the psychrometer came to the Smithsonian).
Ref.: Henry J. Green, Meteorological and Scientific Instruments (Brooklyn, about 1890), p.31.
Location
Currently not on view
date made
1890-1923
maker
H. J. Green
ID Number
PH.308200.1
accession number
70852
catalog number
308200.1
Here, a mercury-in-glass thermometer with a milk white back is held in a black V-shaped housing that is marked “Tycos / ROCHESTER / N.Y. U.S.A.” and that caries a scale extending from -25 to +120 Fahrenheit.
Description
Here, a mercury-in-glass thermometer with a milk white back is held in a black V-shaped housing that is marked “Tycos / ROCHESTER / N.Y. U.S.A.” and that caries a scale extending from -25 to +120 Fahrenheit. The outer brass case is marked “Tycos” at top, and “Taylor / Instrument / Co’s” at the bottom. The Taylor Instrument Companies began operating as such in 1903, adopted the Tycos trade mark around 1908, and donated this instrument to the Smithsonian in 1923.
Ref.: Taylor Instrument Companies, Illustrated and Descriptive Catalog and Price List [of] Thermometers Hydrometers Barometers (Rochester, 1911) p. 111.
Location
Currently not on view
date made
1908-1923
maker
Taylor Instrument Co.
ID Number
PH.308163
catalog number
308163
accession number
70532
An engine indicator is an instrument for graphically recording the cylinder pressure versus piston displacement through an engine stroke cycle. Engineers use the resulting diagram to check the design and performance of the engine.
Description
An engine indicator is an instrument for graphically recording the cylinder pressure versus piston displacement through an engine stroke cycle. Engineers use the resulting diagram to check the design and performance of the engine. This is a replica of the original steam indicator invented in the late 18th Century by James Watt of Scotland. This was the first device intended to measure the varying pressures within a stem engine’s cylinder as it was working.
Originally consisting of only the brass cylinder and piston, Watt’s assistant (John Southern) made the important improvement of the recording tablet and pencil that resulted in the ability to make a lasting recording of a complete cycle of the engine under measurement. The piston of the engine moved the tablet horizontally via an attached cord, and the indicator’s piston moved the pencil vertically. A weight attached to the tablet via a pulley caused the tablet to move back horizontally as the engine’s piston returned to its original position. The result is a steam pressure-volume diagram which is used to measure the efficiency and other attributes of the steam engine.
The introduction of this steam indicator in the late 1790s by James Watt had a great impact on the understanding of how the steam behaved inside the engine's cylinder and thereby enabled much more exacting and sophisticated designs. The devices also changed how the economics and efficiency of steam engines were portrayed and marketed. They helped the prospective owner of a machine better understand how much his fuel costs would be for a given amount of work performed.
Measurement of fuel consumed and work delivered by the engine was begun by Watt, who in part justified the selling price of his engines on the amount of fuel cost the purchaser might save compared to an alternate engine. In the early days of steam power, the method to compare engine performance was based on a concept termed the engine’s “duty”. It originally was calculated as the number of pounds of water raised one foot high per one bushel of coal consumed. The duty method was open to criticism due to its inability to take into consideration finer points of efficiency in real world applications of engines. Accurate determination of fuel used in relation to work performed has been fundamental to the design and improvement of all steam-driven prime movers ever since Watt’s time. And, the steam indicators’ key contribution was the accurate measurements of performance while the engine was actually doing the work it was designed to do.
date made, reproduction
ca 1920s
Associated Date
ca 1796
maker, reproduction
U.S. National Museum
ID Number
MC.309680
catalog number
309680
accession number
107401

Our collection database is a work in progress. We may update this record based on further research and review. Learn more about our approach to sharing our collection online.

If you would like to know how you can use content on this page, see the Smithsonian's Terms of Use. If you need to request an image for publication or other use, please visit Rights and Reproductions.