cylinder electrical machine
Date: circa 1766
Inventory Number: 0013
Classification: Electrical Machine
Dimensions:180 x 185 x 82.2 cm (70 7/8 x 72 13/16 x 32 3/8 in.)
frame: 108 x 183 x 68.5 cm (42 1/2 x 72 1/16 x 26 15/16 in.)
wheel: 130 cm (51 3/16 in.)
Accessories: rope cord belt
glass globe
conducting pad
in folder: photographs, page containing description, history, and discussion of design, note from Ebenezer Gay regarding conservation work, excerpt from David Pingree Wheatland and I. Bernard Cohen, A Catalogue of Some Early Scientific Instruments at Harvard University (Cambridge, MA: Harvard University, 1949), woodcut with picture of instrument from B. Martin, Young Gentleman and Lady's Philosophy (1759): 139.
X-ray images of parts of the machine can be found in C1-A7.
Bibliography:The Apparatus of Science at Harvard, 1765-1800
A Catalogue of Some Early Scientific Instruments at Harvard University
DescriptionElectrostatic generating machine mounted on a wooden frame. A red-painted, rounded glass cylinder is mounted between the spherical tops of two pillars of glass, each of which has a turned wood base. The pillars are coated in pitch, an insulating material. A third pillar has a flat surface at its top with a piece of cloth attached to it. The glass cylinder rubs against this cloth. All of this is mounted on a flat surface that is bolted into a cross beam connecting two legs. The distance between the cloth and the cylinder can be adjusted by sliding the base of the pillar through a pair of rails. The base is slotted in the middle, where a wooden screw with a turned head is used to fasten it in position. Opposite that base is another base that moves in the other direction along the rails. A short turned cylinder with a hole in its top is attached to this base.
The glass cylinder is turned by a rope connected to a large wooden drive wheel with six spokes. The wheel is turned by a brass crank with a wooden handle. The wheel axle rests in grooves carved in wooden pieces bolted to the upper beams of the frame on either side of the wheel. The axle is held in place by a pair of brass pieces screwed into the wood.
The frame resembles that of a tall, thin bed. The four spherical feet are mounted on cylindrical wheels. From the top, the frame appears to be a rectangle with the side supporting the table extended past the corner. The upper beams, which hold the drive wheel, are joined to two legs to the right and a cross beam connected the wider-spaced legs under the surface supporting the glass cylinder. The legs to the right are topped with wood spheres, while the legs supporting the table are buttressed at the top. Many of the flat surfaces of the instrument have a plate taking the form of a gold crest with bilateral symmetry across three equally spaced angles. The crank currently rests in a fitted brass notch screwed into one of the upper beams.
Two X-rays of this object's insulated posts taken by Henry Lie of the Straus Center, HU Art Museums, on 4/6/2006 are stored in C1-A7