1 74: Scientific Intelligence.. 



conduction-current. From 17 sets of observations, each set con- 

 sisting of 18 separate determinations of the deflection and the 

 other quantities involved, the mean value of v thus found was 

 305X10 10 , the determinations which differed from this the most 

 being 2-75 X10 10 and 3'24Xl*0 ,() , respectively. The value of this 

 constant is known to be 3*00 x 10 1 "." Similar results were 

 obtained when discs and condensing plates were divided each 

 into six sectors by radial scratches, thus showing that the effect 

 observed was not due to conduction-currents in their surfaces. 



To prove, further, that the deflection observed was actually due 

 to the magnetic action of the rotating charged discs, a further 

 experiment was tried. The discs were rotated in the same direc- 

 tion and at any instant charged oppositely; and, again, rotated 

 in opposite directions and at any instant charged alike. Their 

 magnetic effects on the coil should then annul one another pro- 

 vided the two discs rotated with the same speed, and this was 

 the result obtained. For example, when the two discs were 

 rotating in same direction with speeds of — 86*9 and —88*8 

 revolutions per second, respectively, and charged alike, the 

 observed deflection was — 66*2; when they were rotating oppo- 

 sitely under the same conditions, with speeds +88*0 and —89*6, 

 the observed deflection was —1-0. 



It is concluded, therefore, that the results obtained " show 

 beyond any doubt that electrical convection does produce magnetic 

 action, or, more exactly, that when the sign of electrification of a 

 moving charged body is changed, an electric conduction-current 

 is induced in a neighboring circuit, of a strength equal to that 

 which would be induced in this circuit by reversing the direction 

 of a conduction-current in a circuit coinciding with the path of 

 the convection-current." 



2. American Association for the Advancement of Science.— 

 The fiftieth annual meeting of the American Association will be 

 held in Denver, August 24 to 31. Professor C. G. Minot of 

 Cambridge will preside as President. The address of the Perma- 

 nent Secretary, Mr. L. O. Howard, is Washington, D. C. (Cosmos 

 Club) until Aug. 15, after that, Brown Palace Hotel, Denver. 

 Information in regard to transportation, hotel accommodation, 

 etc., may be obtained from the Local Secretary, Mr. Arthur 

 Williams, Chamber of Commerce, Denver. 



OBITUARY. 



Dr. Joseph LeConte, Professor of Geology and Natural His- 

 tory at the University of California, died on July 6, at the age of 

 seventy-eight years. A notice is deferred until another number. 



Professor Peter Guthrie Tait, the distinguished Scotch 

 mathematician and physicist, died on July 4, at the age of sev- 

 enty years. He had held the chair of Natural Philosophy in the 

 University of Edinburgh since 1800. His original contributions, 

 chiefly in mathematical physics, were numerous and important ; 

 he was also a lucid and suggestive writer in his treatment of 

 scientific subjects from the popular standpoint. 



