People from ancient times knew that rubbing certain materials and then touching something caused a spark. Studying what is called electrostatics laid the groundwork for understanding electricity and magnetism. Natural philosophers, scientists, and instrument makers created many ingenious devices to generate electrostatic charges starting in the 1600s. These machines varied in size and technique but all involved rotary motion to generate a charge, and a means of transferring the charge to a storage device for use.
This original ink drawing of an electrostatic machine and components dates from about 1750. Signed "H: Carrington Fecit", the caption reads as follows: "A the Body of the Machine B the Globe C the Cufhion D the Spring E the Handle / F the Screw that fastens the whole Machine to the Table G the Slider and Screws that moves the Gun Barrell Nearer or Further / from the Globe HH the Supporters of the Gun Barrell II Crooked pieces that Sufpends Gun Barrell KK Silk Srings upon which / the Gun Barrell is Sufpended L Gun Barrell or Conductor M the Bells N Supporter & Ball to Equilibrition that moves by the Actract- / -tion of the finger or other Object O Bottle & Chain by w:ch the Shock is Given P the Ring Q the Plate R the Small Globe S Wire fixd to the / Ring & Conductor or Gun Barrells T the Hanging Plate V the Stand U the Small Images of thin paper Cut out at pleafure / WWW the feather & Wire".
Early electrostatic machines generated a charge by spinning a globe against a pad. The charge could then be used directly in experiments or transferred from the globe to a Leyden jar. The machine depicted in the drawing is the same type as a machine in the collection--catalog #1983.0190.01.
People from ancient times knew that rubbing certain materials and then touching something caused a spark. Studying what is called electrostatics laid the groundwork for understanding electricity and magnetism. Natural philosophers, scientists, and instrument makers created many ingenious devices to generate electrostatic charges starting in the 1600s. These machines varied in size and technique but all involved rotary motion to generate a charge, and a means of transferring the charge to a storage device for use.
This portable generating machine from around 1760 comes with an experimental kit of accessories. Early electrostatic machines generated a charge by spinning a globe against a pad. The charge could then be used directly in experiments or transferred from the globe to a Leyden jar. The hand-cranked ball of sulfur on this machine rubbed against a leather pad. The pins on the brass rod set close to the ball transferred the charge from the ball to the rod, called a prime conductor. Suspended from a frame by insulating silk threads, the charged prime conductor allowed a researcher to show electrical properties like attraction, repulsion, and strength of charge. Accessories include pith balls, a chime of bells, a Leyden jar, and assorted plates, hooks and dischargers.
This machine is especially interesting as we have an original design drawing in the collection showing this type of machine--catalog #1988.0621.01.
People from ancient times knew that rubbing certain materials and then touching something caused a spark. Studying what is called electrostatics laid the groundwork for understanding electricity and magnetism. Natural philosophers, scientists, and instrument makers created many ingenious devices to generate electrostatic charges starting in the 1600s. These machines varied in size and technique but all involved rotary motion to generate a charge, and a means of transferring the charge to a storage device for use.
This incomplete machine dates from about 1750 and appears to be Benjamin Franklin’s design. In the late 1740s, Franklin began investigating electricity with instruments supplied by friends in Britain. Scientific instruments of all types were in short supply in colonial America so Franklin supplemented his imported equipment with items of his own design. Early electrostatic machines generated a charge by spinning a globe against a pad. The charge could then be used directly in experiments or transferred from the globe to a Leyden jar. The hollow glass globe on this machine rubs against a leather pad seasoned with a specially formulated grease. The charge collector assembly, missing from this machine, consisted of brass pins that rode against the glass and carried the charge to a brass ball set on an insulating glass rod. Princeton University donated this machine in the 1960s and kept a second machine for display there. The exact origin of the two generators is uncertain but an oral tradition at Princeton associates both machines with Franklin.