File:Transactions and proceedings and report of the Philosophical Society of Adelaide, South Australia (1911) (14764005052).jpg

Identifier: transactionsproc3536phil (find matches)
Title: Transactions and proceedings and report of the Philosophical Society of Adelaide, South Australia
Year: 1878 (1870s)
Authors: Philosophical Society of Adelaide, South Australia
Subjects: Philosophical Society of Adelaide, South Australia Science
Publisher: Adelaide : The Society
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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ickness, but reaching a certain maximumvalue, while the target was still easily perforable. This isexhibited in the curve, ABC, shown in fig. 2. Other metalswere found to behave similarly as shown in the curve, DEC,given for sheet-copper, the maximum ionization being thesame in all cases, but the critical thickness decreasing withincreasing density of the metal. The curve, FGC, is forsheet-zinc. When the bullet perforates a target of sheet-metal theair in front of the target is found to be ionized, but prac-tically no ionization could be detected in the air behind thetarget. For example, with the electrode and chamber infront a reading of 34 scale divs. was obtained, whereas thereading when both were transferred to the rear was only0*32 scale divs. If two perforable targets were placed in series the totalionization was found to be equal to the sum of the ioniza-tions produced by each separately, provided the front targetis not allowed to act as an electrostatic shield to the rear one.
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6 Cleaning the surface of the target produced little if anydifference in the magnitude of the effect; neither was anyvariation observed when a light target was backed by a heavymetal plate. The mobility of the ions was roughly determined by amodification of Langevins method (J. J. Thomson, Conductionof Electricity through Gases, 2nd Ed., p. 64). The distance ofelectrode from target was 1*9 cm. and the P.D. 600 volts.The curve showing the number of ions collected when theelectrometer circuit was closed at different intervals afterimpact of the bullet is shown in fig. 3. This curve, for —veions, shows three tolerably distinct kinks at A, B, C, dueto species of ions having mobilities 2x10-^ cm./sec. pervolt/cm., 4x10-4 cm./sec. per volt/cm., and r2xl0-3cm./sec. per volt/cm. The coefficient of recombination wasfound to be of the mean value 38 e. The dependence of the ionization produced on the velocityof the bullet was investigated by allowing the bullet toimpinge after penetrating vary

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