rolling sphere planimeter
Date: 1907
Inventory Number: 1997-1-0250
Classification: Planimeter
Subject:
Maker: Gottlieb Coradi (1847 - 1929)
Cultural Region:
Place of Origin:
Dimensions:
case: 9.5 × 33.5 × 24.1 cm (3 3/4 × 13 3/16 × 9 1/2 in.)
Accessories: carrying case
DescriptionRolling sphere planimeter in a rectangular, wooden box. Planimeter consists of a long metal tracer arm with a stylus on the end, attached to a black metal frame containing two silver wheels. The tracer arm is attached to the frame by a clamp and a spring. On top of the frame, between the two wheels, is a metal bar. There is a white plastic dial, displaying the numbers 1-45 in intervals of five, on top of the end of the bar closest to the tracer arm. A white plastic vernier scale is wrapped around the other end of the bar. The rounded edge of a hemispherical piece of metal is in contact with the side of the bar. There are several objects not attached to the planimeter: a graduated, adjustable metal bar [an extension to the tracer arm?], a shorter, flat metal bar, a metal bar with a square cross-section, a brass roller with hooks on either side, and a small brush.
The inside of the box is felt. There are three pieces of paper attached to the inside of the lid. The top one contains a four-column table with the printed headings "Scales/Position of the vernier on the tracer bar/Value of the unit of the vernier on the measuring roller/Constant." The values are filled into the table by hand, the "Constant" column left blank. At the bottom of the table, "Zurich, the 12 Februar. 1907. No. 2232. G Coradi," is written, the date and the no. written in by hand.
Below the table are instructions typed in German. To the left of the German instructions is a typed translation that reads as follows: "(translation of instructions) / to take the instrument from the case, hold it with the right hand on the large frame, never by the frame of the measuring roller, and with the left hand hold the tracer arm. Lift carefully from the case without the use of force with the left hand." In handwriting it is written, at the top of the card: "To read sq. inches, set vernier on 3258."
The inside of the box is felt. There are three pieces of paper attached to the inside of the lid. The top one contains a four-column table with the printed headings "Scales/Position of the vernier on the tracer bar/Value of the unit of the vernier on the measuring roller/Constant." The values are filled into the table by hand, the "Constant" column left blank. At the bottom of the table, "Zurich, the 12 Februar. 1907. No. 2232. G Coradi," is written, the date and the no. written in by hand.
Below the table are instructions typed in German. To the left of the German instructions is a typed translation that reads as follows: "(translation of instructions) / to take the instrument from the case, hold it with the right hand on the large frame, never by the frame of the measuring roller, and with the left hand hold the tracer arm. Lift carefully from the case without the use of force with the left hand." In handwriting it is written, at the top of the card: "To read sq. inches, set vernier on 3258."
Signedon frame and inside case: G Coradi.
Inscribedon frame: Zurich Switzerland No. 2232
inside case: Zurich, the 12 February 1907. No. 2232.
inside case: Zurich, the 12 February 1907. No. 2232.
FunctionA rolling sphere planimeter is used to measure the area of a plane figure.
According to the website of Robert Foote, faculty member at Wabash College, planimeters measure area "by moving a tracer point around the boundary of the region being measured. As the tracer point moves the wheel partially rolls and partially slides on the paper, recording its motion perpendicular to the tracer arm. It turns out that when the tracer point returns to the point where it started, the net roll of the wheel is proportional to the area of the region. If a scale attached to the wheel is calibrated appropriately, the area can be read from the scale."
For a detailed description of how the rolling sphere planimeter measures area, see:
J.C. Maxwell, "Descriptions of a New Form of Planometer, an Instrument for Measuring the Areas of Plane Figures Drawn on Paper," in The Scientific Papers of James Clerk Maxwell, Vol. 1, ed. W. D. Niven (Mineola, NY: Dover Publications, 2003), 230-237. [Reprint of original 1890 publication by Cambridge University Press.]
According to the website of Robert Foote, faculty member at Wabash College, planimeters measure area "by moving a tracer point around the boundary of the region being measured. As the tracer point moves the wheel partially rolls and partially slides on the paper, recording its motion perpendicular to the tracer arm. It turns out that when the tracer point returns to the point where it started, the net roll of the wheel is proportional to the area of the region. If a scale attached to the wheel is calibrated appropriately, the area can be read from the scale."
For a detailed description of how the rolling sphere planimeter measures area, see:
J.C. Maxwell, "Descriptions of a New Form of Planometer, an Instrument for Measuring the Areas of Plane Figures Drawn on Paper," in The Scientific Papers of James Clerk Maxwell, Vol. 1, ed. W. D. Niven (Mineola, NY: Dover Publications, 2003), 230-237. [Reprint of original 1890 publication by Cambridge University Press.]
Curatorial RemarksSee the instrument's file for more information about rolling sphere planimeters and an illustration of one made by G. Coradi (Zurich); also see the file for 1995-1-0003 for more information about planimeters in general.
ProvenanceOn March 13, 1997, the instrument was picked up from the Howard H. Aiken Computation Laboratory, 33 Oxford Street. The instrument was transferred to the Collection by Edward P. Jackson, Facilities Manager in the Division of Engineering and Applied Sciences. The instrument was housed on a shelf in a storage room beneath the entrance gallery.