File:The London, Edinburgh and Dublin philosophical magazine and journal of science (1902) (14780447434).jpg

Identifier: londonedinburgh641902lond (find matches)
Title: The London, Edinburgh and Dublin philosophical magazine and journal of science
Year: 1840 (1840s)
Authors:
Subjects: Science
Publisher: London : Taylor & Francis
Contributing Library: Smithsonian Institution Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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of an auxiliary electroscope), and then to makecontact with p by means of the iron wire r. When asuitable charge has been given the magnet is removed andthe contact thus broken, s is then touched to discharge it.When c and the electroscope were exhausted insulation wasso good that the potential of the system did not sink morethan a fraction of a volt in 24 hours when initially charged toabout 100 volts. In order to raise the temperature of the w7ire a, the vesselc was inclosed in a metal oven heated by a gas-burner. Inthis oven was also placed an elongated glass bulb containingair. This worked a temperature-regulator in the ordinaryway, cutting off the gas by its expansion when the tempe-rature rose too high. The neck / of the vessel was long enough to prevent theelectroscope getting seriously heated by the radiation from 112 100 Hon. R. J. Strutt on the Discharge of the gas-burner when screens were interposed. As, however,the electroscope was exhausted, to improve the insulation, the
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&3l3H/0A/t/tV gold-leaf was liable to show radiometer effects. These couldbe greatly mitigated by not pushing the exhaustion of theelectroscope too far. Positive Electrification by Hot Metals, 101 The electroscope was observed with a microscope provided witha scale in its eyepiece. It was found, on comparing the scaleof the electroscope with a multicellular voltmeter, that the divi-sions were of approximately equal value throughout the scale,very nearly one volt per division. The scale had 50 divisions. When the apparatus was filled with air at atmosphericpressure a leak was observed at ordinary temperatures. Thiseffect is quite distinct from the effect discovered by Guthrie,since it is observed equally whether the charge is + or —(Wilson, loc. cit.), whereas Guthries effect is only obtainedwith a + charge, unless the temperature is above a red heat.To make this effect insensible the pressure was reduced to1 cm. of mercury. The Guthrie effect is not apparentlymuch affected by mo

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