( 809 ) 



Physics. "On flic influence which irradiation exerts on the electrical 

 conductivity of Antimonite from Japan" '. P>\ Dr. V. M.Jaeger. 

 (Communicated by Prof. P. Zkkman). 



(Communicated in the meeting of February 23, 1U07). 



§ 1. Having been occupied for a considerable time with the 

 determination of the specific electrical resistance in the three crys- 

 tallographic main directions of the antimonite from Shikoku (Japan), 

 I had already found that with this substance, which belongs to the 

 very bad conductors, inexplicable irregularities presented themselves, 

 when the resistance was determined several times anew during a 

 long time, with identical electromotive force. 



Generally the obtained deflection of the galvanometer first became 

 larger and larger, and decreased again in course of time, after which, 

 as I found, periodical increase and decrease sometimes followed. It 

 was impossible to detect any connection between tension, intensity 

 of current, and time. 



As for rods of a length of some centimeters and a section of about 

 a quarter of a square centimeter, resistances were found in the different 

 directions lying between 500 and 20000 millions of Ohms, 1 first 

 thought of an impregnation of the electrical charge in the ill-con- 

 ducting material. On account of its opposed direction, however, an 

 eventual polarisation current would have to cause an apparent increase 

 of the resistance, whereas experience generally showed a decrease of 

 the initial resistance. 



§ 2. While I was trying to ascertain the cause of these deviations, 

 a sunbeam fell through an aperture of the curtain on the piece of 

 mirror-glass which closed the THOMSON-galvanometer, and was partially 

 reflected to the apparatus containing the piece of antimonite, cut 

 with its longitudinal direction parallel to the crystallographic />-axis. 

 The needle of the galvanometer deflected immediately towards that 

 side in which the total deflection was increased. At first I thought 

 that the heat of the sun penetrating the galvanometer on one side 

 had changed the cocoon thread so much as to cause a torsion. Some 

 moments later, however, when I happened to light a match in the 

 neighbourhood of the preparation, the increase of the already existing 

 dellection was repeated, and now in the same sense as before, and 

 at the same time stronger. 



$ 3. So we have met here with a new phenomenon. Either the 



