4. First case study – the subdivision of the light - HM Treasury

F05 Ch4 Subdivision of the light.doc
05/04/2006 19:34:00
Technological roulette – a multi-disciplinary study of the dynamics of innovation in electrical, electronic
and communications engineering.
4. First case study – the subdivision of the light
4.2 Electrical science in the seventeenth, eighteenth and nineteenth centuries
Prior to the beginning of the nineteenth
century, knowledge of electricity and
magnetism was based mainly on observation of
natural phenomena. The ancients were familiar
with the electrostatic properties of insulating
materials such as sulphur and amber and the
north-seeking ability of lodestone. William
Gilbert, physician to Queen Elizabeth1,
published an early treatise, De Magnete, in
1600. In 1672, Otto von Güricke generated a
static charge by means of frictional machine
consisting of a sulphur ball and a rotating
mechanism. In 1745 Muschenbroek and
Cunæus invented the Leyden jar as a means of
storing such charges.
Fig. 4.1 An electrician’s laboratory, about 1782
from the Complete Treatise of Electricity by T. Cavallo
Fig. 1 Cylindrical influence machine Fig. 5 Henley’s universal discharger
Fig. 2 Prime conductor with Henley’s quadrant Fig. 7 Henley’s quadrant electrometer
electrometer Fig. 10 Battery of Leyden jars
Fig. 4 Stand of electrometers of various types Fig. 11 Simple Leyden jar, with discharger
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Jarvis 1955 a
Jarvis 1955a
Fig. 4.2 Magnetising a bar lying on the
meridian from William Gilbert’s De
Magnete
JJehl 1937
Fig. 4.3 Von Güricke’s sulphur ball
(1692)