File:Transactions and proceedings and report of the Philosophical Society of Adelaide, South Australia (1911) (14764335685).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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distance from it of about 1*5 cm. andinsulated as shown with sulphur and guard-ring. Targetand electrode are enclosed in hollow metal box, the lid, CD,of which is removable. This box with the target can beraised to any desired potential by means of a battery of500 small accumulators and the charge driven on to theelectrode measured by a Dolezalek electrometer of suitablyarranged sensibility. In making measurements of the total ionization theelectrometer reading (mean of two or three successiveswings) was taken 15 seconds after impact of the bullet,in which time practically all ions of a given sign producedin the chamber were found to be collected. A number ofmeasurements (usually five or six) were made in eachexperiment and the arithmetic mean of these taken. Theamount of variation in the effect is indicated by the meanerror of these measurements. Where necessary, correctionwas made for the natural leak of the instrument. The order Notes on Ionization by Impact, by Kerr Grant, M.Sc. 3
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4 of magnitude of the effect when a 1-gram bullet strikes ametal target with a velocity of about 700 ft. per second issix E.S. units, and approximately the same for -(-ve and —veions, i.e., one E.S. unit per 3 x 10^ ergs of kinetic energydestroyed. Little variation was produced by varying thematerial of the target so long as this is of metal. Thi^ isshown by the following table of measurements: — Material of Target. Reading, Lead (A) 16 jt 3 (H) 69 + 4 Iron (A) 35 J: 3 (B) 60 + 3 Zinc (A) 36 ± 3 Copper (A) 34 Brass (B) 63 Two sets of observations (A) and (B) are tabulated, the sensi-bility of the electrometer being higher in the latter set. Thelead target used in (A) had been battered by previous usage,that in (B) was a fresh plate. This is the probable cause ofthe anomalous behaviour of the lead in the first case. Whena wooden target was used the deflection of the electrometerneedle was very much smaller than in the above cases. In the above cases the target was not perforated b

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