Department of History
University of California, Irvine
Instructor:    Dr. Barbara J. Becker

Lecture 14.  Electricity and Magnetism.

Subtle Fluid of Electricity
What, exactly, is electricity?  When we look in our Microsoft Encarta encyclopedia, we see that electricity is defined as a "class of physical phenomena resulting from the existence of charge and from the interaction of charges."  What does this mean, in layperson's terms?  It means that whoever wrote the Microsoft Encarta encyclopedia is a big fat dope.  Because we know from our junior high school science training that electricity is actually a fast-moving herd of electrons, which are tiny one-celled animals that can survive in almost any environment except inside a double-A battery, where they die within minutes.
--Dave Barry

All substances can be electrified by friction.

Electrical fluid must be universally fixed in matter.

Electrical activity, unlike gravity, can be controlled in experiment

  • much stronger than gravity
  • repels as well as attracts
  • behaves like a subtle fluid should
To be able to analyze electricity -- must produce it,

Francis Hauksbee's Electrical Fluid Generator (c. 1705)

collect it,

The Leyden jar:  In Leyden, Holland (1746), Petrus van Musschenbroek (1692-1761) filled a jar with electrical fluid.

and measure it.

  • Unclear, however, what to measure, or how to measure it.

Charles Coulomb (1736-1806)

Coulomb's Torsion Balance (1785)

Strength of electrical force can be measured and calculated in a manner analogous to that of gravity:
Working within the Subtle Fluid Paradigm

Subtle fluid model spawned --

  • new instruments
    • air pump
    • pneumatic trough
    • electrostatic generator
    • Leyden jar
  • new knowledge
    • "air" is not an element (dephlogisticated air, fixed air, inflammable air....)
    • "water" is not an element (a mixture of dephlogisticated air and inflammable air)
    • electrical force is directly analogous to gravitational force
  • new questions
    • "What will happen to plants and animals that are exposed to electrical fluid for long periods of time?"
  • new institutions
    • École Polytechnique -- a national school established in France to provide the best scientific and engineering education so they may work to improve the lives of all French citizens
      • prominent instructors -- Pierre Simon de Laplace (1749-1827) and Claude Louis Berthollet (1748-1822)
  • Society of Arcueil -- program established and directed by Laplace and Berthollet to encourage experimental work by outstanding students at École Polytechnique; investigations focused on short-range forces of interaction between the tiny particles of matter and the subtle fluids that permeate them.
    • "Students" at Arcueil:
      • Charles Augustus Coulomb (1736-1806)
      • Jean Baptiste Joseph Fourier (1758-1830)
      • Étienne Louis Malus (1775-1812)
      • Joseph Louis Gay-Lussac (1778-1850)
      • Dominique François Arago (1786-1853)
      • Auguste Jean Fresnel (1788-1827)
Subtle Nervous Fluid?
Jan Swammerdam (1637-1680)
  • muscles contract in response to irritation of related nerves

Is muscle fiber imbedded with "nervous fluid"? -- Swammerdam (1664)

Luigi Galvani (1737-1798)
  • nerveo-electric fluid is inherent in all animal matter
  • produced in the cerebrum
  • conducted by nerves to muscles
  • muscle fiber is like a Leyden jar
    • -inside positively charged
    • -outside negatively charged
  • muscle fiber stores electric fluid
  • fluid is released when nerves are stimulated

Electricity causes muscles to contract -- Galvani (1781)
Pierre Bertholon de Saint-Lazare (1742-1800)
  • humans and animals possess a spontaneous or animal electricity.
  • health depends on having the right amount of electrical fluid.

Disease can be treated by exposure to electricity -- Bertholon (1786)

Alessandro Volta (1745-1827)

  • 1800 -- finds that electricity can be generated in chemical reactions

Are chemical and electric fluids different manifestations of the same thing?
William Herschel (1738-1822)
  • 1800 -- finds an invisible source of heat beyond the red end of the visible spectrum.
Are luminous and caloric effects different manifestations of the same thing?
Johann Ritter (1776-1810)
  • 1801 -- looks for and finds an invisible source of chemical activity beyond the violet end of the visible spectrum.
Are luminous and chemical effects different manifestations of the same thing?
Hans Oersted (1777-1851)
  • 1820 -- looks for and finds evidence for magnetic influence in the air around a current-carrying wire.

Are magnetic and electric fluids different manifestations of the same thing?

If subtle fluids are supposed to act independently, how can apparent relationship between chemical effects, animating action, and electricity be accounted for?
Naturphilosophie -- nature philosophy

The whole is greater than the sum of its parts.  To really know the world, an investigator must grasp whole first, otherwise understanding of parts can be meaningless.

  • Vernunft -- reason (intuition, not 18th c reason)
    • direct grasp of knowledge
    • a powerful and integrating force
  • Verstehen -- understanding
    • deliberate and analytical acquisition of knowledge
    • useful but secondary to Vernunft

Experiment forces nature to behave abnormally.

  • Subjecting nature to inquisition forces it to comply with inquisitor's expectations.
  • Questions asked are limited by human imagination.
Kepler -- not Newton -- is the hero of Naturphilosophen (the Nature Philosophers).  Kepler used Vernunft:
  • grasped nature of world system by intuition
  • saw universe with an inner eye
  • real genius
Newton used Verstehen:
  • analyzed parts
  • failed to grasp the essence of the whole
Old view [held by mechanical philosophers]:
  • All motion is transmitted in two ways:
    • simple collisions between inert particles, and/or
    • mystery mechanism of "action at a distance".

New view [held by Naturphilosophen]:

  • All motion is the result of the interaction of opposites -- a dialectic process that produces a tension that permeates space.
  • This tension causes all physical activity we observe.
  • Its source is positive and negative electricity.

Iron filings reveal the magnetic "tension" between opposite poles in the space surrounding a magnet.
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