750 



SCIENCE. 



[N. S. Vol. III. No. 72. 



LEE. The author presents some notes on X-ray 

 photographs of minerals and thin sections of 

 rocks ; the article is accompanied by an illus- 

 tration. 



SOCIETIES AND ACADEMIES. 

 ACADEMY OF SCIENCE OF ST. LOUIS. 



At a meeting of the Academy on May 4th 

 Prof. Nipher read a preliminary paper on A 

 Botational Motion of the Cathode Disc of the 

 Crookes Tube. 



He had been studying the change in the char- 

 acter of the Crookes effects due to long contin- 

 ued operation. It was observed that the cath- 

 ode disc of aluminum was slightly loose, and 

 that it was rocking to and fro in rotary motion 

 on the aluminum wire. It finally became loos- 

 ened and started into a slow rotation. The 

 motion was a halting one, as the disc was out 

 of balance and the bearings were rough. When 

 stopped by pinching in the bearing, it began to 

 struggle and rock against the restraint and 

 would finally become loosened again and con- 

 tinue its motion. 



It was impossible to either accelerate or re- 

 tard the motion by powerful bar magnets, ap- 

 plied as in Barlow's wheel. Change in position 

 with respect to the earth's field or the induc- 

 tion coil produced no effect on the rotation. 

 Looking at the disc from the point where the 

 cathode wire enters the tube, the disc rotates 

 counter clockwise. The brush discharge of a 

 Holtz machine yielded even better results than 

 the induction coil when the leading conductors 

 were separated by spark intervals. 



The rotation has not yet been obtained be- 

 tween spark terminals in air of ordinary pres- 

 sure nor when the movable disc forms the 

 anode, but work on these points is not yet con- 

 cluded. 



Prof. Nipher stated that the experimental 

 evidence thus far indicates that the effect is due 

 to action and reaction between the cathode 

 plate and the radiant matter. If so, the radiant 

 matter starts from the disc in a vortex, whose 

 axis passes through the dark spots opposite the 

 disc faces. It may also be due to direct action 

 and reaction between the disc and the surround- 

 ing field due to the current. He is now having 

 apparatus constructed which will determine be- 



tween the possible explanations. Prof. Nipher 

 stated that he had long sought some experi- 

 mental basis for imposing a condition of rota- 

 tion upon the equations for force and potential 

 within a wire conductor. Without such term 

 the equations lead to absurd results. 



Dr. E. C. Eunge described an interesting case 

 of insanity, unrecognized for twenty-eight years. 

 William Teelease, 

 Recording Secretary. 



NEW YOBK academy OF SCIENCES. — SECTION OF 



ANTHROPOLOGY, PSYCHOLOGY AND 



PHILOLOGY. 



The Academy met on April 27th, with Presi- 

 dent Stevenson in the chair, and proceeded to 

 organize the new Section in Anthropology, Psj'- 

 chology and Philology. Prof. N. M Butler was 

 chosen temporary chairman. 



Prof. F. H. Giddings was nominated and 

 elected Permanent Chairman of the section; Dr. 

 Livingston Farrand, Secretary of the sub-sec- 

 tion of Anthropology and Psychology, and Prof. 

 A. V. Williams Jackson, Secretary of the sub- 

 section of Philology. The ofiioers were elected 

 for a term that will end at the annual meeting 

 of the Academy, and it was resolved that the 

 two svib-sections meet in alternate months. 



Prof F. H. Giddings read a paper on A Plan, 

 for the Systematic Study of tribally organized So- 

 cieties, which will be printed in Science. 



Prof J. McKeen Cattell described a Method 

 for Determining Photometric Differences by the 

 Time of Perception. A series of gray surfaces 

 was exhibited making over 200 nearly eqvial 

 shades between black and white. The shades 

 are so nearly alike that they cannot be distin- 

 guished with certainty, and when the observer 

 attempts to sort them out in order an error of 

 displacement occurs which measures his accur- 

 acy of discrimination. With nine observers the 

 error varied from 6.04 to 11.05, the average 

 being 8.1, from which it follows that about 25 

 shades can be distinguished between black and 

 white. The relation of the error of observation 

 to the brightness of the light was shown. The 

 speaker further described experiments now be- 

 ing carried out with the same gray surfaces, in 

 which the time it takes to distinguish the differ- 

 ence between two sensations is used to measure 



