Intelligence and Miscellaneous Articles. 24i 



enthusiastic author, whose scientific acumen, wide knowledge, and 

 judicious treatment of the varied subjects of his compilation are 

 certainly further proved by this volume. As yet, he informs us in 

 the Preface, the enterprise has not been profitable ; but he hopes 

 that it will be successful by the co-operation of more and more 

 Subscribers ; and indeed we sincerely hope that this handy and 

 valuable Annual will be worthily supported. 



XXI. Intelligence and Miscellaneous Articles. 



ON THE NATURE OF THE REFLEXION OF ELECTRICAL WAVES AT 

 THE END OF A CONDUCTING WIRE. BY MM. KR. BIRKELAND 

 AND E. SARASIN. 



TN a communication of April 17, 1893, one of us attempted, 

 •*- starting from the theory of the motion of electromagnetic energy 

 in space, to make a hypothesis on what takes place in the vicinity 

 of the end of a metal wire along which electrical waves are passing. 



We have examined the question together, exploring the electrical 

 field about the end of the wire, with small resonators of 10 to 25 

 centim. in diameter, and although the point of view explained in 

 the note in question has not been confirmed in all points by our 

 results, they form none the less an interesting experimental con- 

 tribution to the remarkable theories of Prof. Poynting. 



The electrical waves were furnished by a small plate-exciter, the 

 sparks of which, about 3 millim., passed in oil. Opposite one of 

 these primary disks was a similar one from which proceeded a 

 copper tube 1 centim. in diameter and 9 metres in length. This 

 tube was supported on thin wooden rods 1*5 metre high. 



The resonators were circular and fixed vertically with the spark 

 uppermost ; they had a double motion — they could be rotated about 

 a vertical axis passing through the spark, and they could also be 

 moved parallel to the conducting tube. 



"We arranged so that even in darkness we could mark the 

 distance from the centre of our resonator to the end of the con- 

 ducting wire, measured parallel to the wire, and also the angle 

 which the plane of this formed with the wire. 



The observations were made by means of a telescope mounted 

 horizontally at a distance of a metre from the circle, which is 

 necessary owing to the considerable disturbance produced by the 

 body of the observer on the rapid oscillations. 



Our researches were directed to two points principally : we first 

 determined the four first nodes in seven different distances from 

 the wire; the plane of the circle being always normal to this. 

 These nodes are each determined by at least ten measurements ; 

 the numerical results thus obtained for the circle of 10 centim. are 

 given in the subjoined table. The different distances of the resonator 

 from the .conducting wire are counted from the axis of this latter 

 to the nearest point of the circle. The numbers in each column 

 give the distance of each node to the normal at the end of the wire. 



