Edison's Asst. Charles Lorenzo Clarke Signed Drawing & Manuscript, "Edison's Electrical Pressure Indicator"
Thomas Edison
n.p., December 29, 1881
Edison's Asst. Charles Lorenzo Clarke Signed Drawing & Manuscript, "Edison's Electrical Pressure Indicator"
Signed original drawing & manuscript
Two items relating to electrical engineer Charles Lorenzo Clarke (1853-1941), who served as an assistant of prolific inventor Thomas Edison (1847-1931) at Menlo Park, New Jersey, in the early 1880s. Ca. December 29, 1881. N.p. The lot includes an original signed pencil drawing completed in Clarke's hand; as well as a 2pp handwritten manuscript accompanying this diagram, docketed "Diagram and Description of Edison's Electrical Pressure Indicator June 1882." Expected wear and weathering which will be elaborated below, else very good. The largest item, the drawing, measures 8" x 10".
Clarke had graduated from Bowdoin College with a civil engineering degree in 1875. After studying in Europe, he returned to the United States and secured a job with Thomas Edison in early 1880. Clarke had no knowledge of electrical engineering prior to his working at Edison's laboratory, but his superior math abilities quickly made him indispensable. As Zorina Kahn, Professor of Economics at Bowdoin College, explained in a 2024 blog post, specifically, Clarke "calculate[d] the dimensions and cost of conductors to enable the functioning of a central station system. Edison also depended on Clarke's work for the design and development of efficient dynamos with greater electrical capacity, and an effective electrical distribution system." In 1882, Clarke was promoted to serve as Chief Engineer of Edison Electric Light Company in New York City.
The diagram and manuscript both relate to the electrical pressure indicator - also known as the pressure gauge or voltmeter - which was a device used to measure electrical potential difference (voltage) within an electrical circuit. This was a tool essential to maintaining a stable and reliable power distribution.
The lot includes:
1. A 1p original pencil drawing all in Clarke's hand, signed by him as "Chas. L Clarke" at bottom, and with approximately 45 other words in his hand found throughout describing elements of Edison's Electrical Pressure Indicator. December 29, 1881. N.p. Clarke's captions include: "Bell magnet / 6.3 ohms"; "Connection for A line"; "Total resis. 92.7 ohms"; "Cut in 9 turns / for local bell," along with many others. Some light pencil notes verso. Even toning. Flattened transmittal folds, with isolated chips and closed tears along the folds. 8" x 10".
2. A 2pp manuscript accompanying the drawing, docketed "Diagram and Description of Edison's Electrical Pressure Indicator June 1882" on the outer leaf of p. 2. Pen-inscribed on two sheets of laid watermarked paper with "The Edison Electric Light Co., / 65 Fifth Avenue" pre-printed letterhead. Isolated edge darkening and minor smudges, else near fine. 5.625" x 9".
In part:
"Each of the three resistance spools is 6" long by 2" square and 9 threads to the inch with an average of 50 turns of wire on each spool…
The bell magnet has approximately a resistance of 6 to 6.5 ohms and is a shunt around 9 turns of the resistance wire on the spool. The spring for holding the armature has 25 turns of spring brass wire .093" diam. And is wound on an inch mandril and is stretched to 6 1/2" length…
The indicator must get to the normal warmth (on magnets) before indicating correctly, their being several volts difference between its being warm or cold…"
This item comes with a Certificate from John Reznikoff, a premier authenticator for both major 3rd party authentication services, PSA and JSA (James Spence Authentications), as well as numerous auction houses.
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Thomas Edison
n.p., December 29, 1881
Edison's Asst. Charles Lorenzo Clarke Signed Drawing & Manuscript, "Edison's Electrical Pressure Indicator"
Signed original drawing & manuscript
Two items relating to electrical engineer Charles Lorenzo Clarke (1853-1941), who served as an assistant of prolific inventor Thomas Edison (1847-1931) at Menlo Park, New Jersey, in the early 1880s. Ca. December 29, 1881. N.p. The lot includes an original signed pencil drawing completed in Clarke's hand; as well as a 2pp handwritten manuscript accompanying this diagram, docketed "Diagram and Description of Edison's Electrical Pressure Indicator June 1882." Expected wear and weathering which will be elaborated below, else very good. The largest item, the drawing, measures 8" x 10".
Clarke had graduated from Bowdoin College with a civil engineering degree in 1875. After studying in Europe, he returned to the United States and secured a job with Thomas Edison in early 1880. Clarke had no knowledge of electrical engineering prior to his working at Edison's laboratory, but his superior math abilities quickly made him indispensable. As Zorina Kahn, Professor of Economics at Bowdoin College, explained in a 2024 blog post, specifically, Clarke "calculate[d] the dimensions and cost of conductors to enable the functioning of a central station system. Edison also depended on Clarke's work for the design and development of efficient dynamos with greater electrical capacity, and an effective electrical distribution system." In 1882, Clarke was promoted to serve as Chief Engineer of Edison Electric Light Company in New York City.
The diagram and manuscript both relate to the electrical pressure indicator - also known as the pressure gauge or voltmeter - which was a device used to measure electrical potential difference (voltage) within an electrical circuit. This was a tool essential to maintaining a stable and reliable power distribution.
The lot includes:
1. A 1p original pencil drawing all in Clarke's hand, signed by him as "Chas. L Clarke" at bottom, and with approximately 45 other words in his hand found throughout describing elements of Edison's Electrical Pressure Indicator. December 29, 1881. N.p. Clarke's captions include: "Bell magnet / 6.3 ohms"; "Connection for A line"; "Total resis. 92.7 ohms"; "Cut in 9 turns / for local bell," along with many others. Some light pencil notes verso. Even toning. Flattened transmittal folds, with isolated chips and closed tears along the folds. 8" x 10".
2. A 2pp manuscript accompanying the drawing, docketed "Diagram and Description of Edison's Electrical Pressure Indicator June 1882" on the outer leaf of p. 2. Pen-inscribed on two sheets of laid watermarked paper with "The Edison Electric Light Co., / 65 Fifth Avenue" pre-printed letterhead. Isolated edge darkening and minor smudges, else near fine. 5.625" x 9".
In part:
"Each of the three resistance spools is 6" long by 2" square and 9 threads to the inch with an average of 50 turns of wire on each spool…
The bell magnet has approximately a resistance of 6 to 6.5 ohms and is a shunt around 9 turns of the resistance wire on the spool. The spring for holding the armature has 25 turns of spring brass wire .093" diam. And is wound on an inch mandril and is stretched to 6 1/2" length…
The indicator must get to the normal warmth (on magnets) before indicating correctly, their being several volts difference between its being warm or cold…"
This item comes with a Certificate from John Reznikoff, a premier authenticator for both major 3rd party authentication services, PSA and JSA (James Spence Authentications), as well as numerous auction houses.
WE PROVIDE IN-HOUSE SHIPPING WORLDWIDE!
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