portable cyclinder electrical machine in a box
Date: circa 1800
Inventory Number: 0014
Classification: Electrical Machine
Dimensions:23.7 x 32 x 30.2 cm (9 5/16 x 12 5/8 x 11 7/8 in.)
glass cylinder: 7.6 x 7.6 x 14.5 cm (3 x 3 x 5 11/16 in.)
Leyden jar height: 18 cm (7 1/16 in.)
Accessories: Two insulated charge transfer wands.
Bibliography:The Apparatus of Science at Harvard, 1765-1800
DescriptionThis portable electric machine resides in a box with accessories for storing and transferring electricity. It is English-made, circa 1800, with 19th century repairs.
The belt-driven glass cylinder is operated by hand crank. The large wooden wheel has concentric circles as decoration. So does the smaller wooden wheel. Pins on the rims of the wheels meet holes in a leather belt. The hand-crank shaft is of iron. The handle is pine, and seems to be a later replacement.
The mahogany supports for the glass cylinder are clamped to matching, wooden posts attached to a common base. Key-shaped bolts hold them together. On one side of the cylinder is a silver metal comb to collect the electric charge. The comb is held in a brass collar attached to a glass handle, which sits in a socket like a candle. The socket is also made of wood and is attached to the upright supports by an arm. On the other side of the cylinder, there exists a metal stand holding a leather cushion and a rectangle of blue silk. The stand can be moved closer to the cylinder by means of a wing bolt. This metal hardware is painted black and is of later vintage than the wooden supports.
The supports for the crankshaft and cylinder axel match in style and date.
Also in the box, there is a Leyden jar sitting on a lead plate. The jar is held fast by a tin collar and two legs. One leg is separated from the collar. The conductor into the jar is iron topped by a brass ball. A silver Rollo chain goes from the comb to the conductor.
Near the Leyden jar, there is a turned wooden pillar fixed to the box bottom. It supports a glass rod topped by a brass collar with an iron, swing-arm discharger with a brass ball on the end. The glass rod has a hollow center (like it was intended for a thermometer).
Also in the box, there are two portable dischargers, one of which matches the discharger already mentioned. It has a straight iron rod held in a brass collar on a glass handle with a hollow center. There is a brass ball on top. The second is made of hard rubber and has a brass ball glued to it. These are 19th century additions or replacements.
The box lid is loaf shaped. It has a slot for the hand crank to stick out. Match marks (IIIII) are cut into the side edge of the box base and the matching side of the lid. The box bottom has an eyelet and pin on the outside to attach grounding wires or chains.