Dkikmbkr 4, 1903.] 



SCIENCE. 



Corresponding points of the two retinas are 

 those which answer to proportional degrees of 

 rotation of the eyes about the center of rota- 

 tion, and which, from given individual points 

 in the plane of fixation, each receive incident 

 rays whidi must jiass through the nodal points. 

 Tliey represent, tliereforc, the relation between 

 ilie muscular and the retinal senses. 

 Intelligence and Movement: Dr. R. S. Wood- 

 worth, Columbia University. 

 In discussing the relations of ' Intelligence 

 and Movement,' Dr. Woodworth argued that 

 the mental cue of a voluntary movement was 

 not ordinarily a kinesthetic image of the move- 

 ment. Even in learning a new movement, 

 experiment shows that no such image need be 

 present. Since voluntary movement is de- 

 veloped from instinctive, the original mental 

 cue must have been that provided by instinct, 

 and the instinctive cue is never an image of 

 the movement about to be made. The actual 

 sensation of a movement can evidently not be 

 the stimulus to that same movement, and the 

 reproduced sensation can hardly have a motor 

 power not possessed by the sensation itself. 



The Minimal Value of the Psychophysical Re- 

 action-Time: Professor Lightner Witjier, 

 University of Pennsylvania. Read by title. 

 Primary and Secondary Presentations: Mr. 

 H. R. Marshall, New York City. Read by 

 title. 



James E. Lough, 



Secretary. 



section of astronomy, physics and chemistry. 



At the meeting of the section on November 

 2, Dr. Bergen Davis read a paper on ' The 

 Electrical Conductivity and Absorption of 

 Energy in the Electrodeless Discharge.' 



The discharge was produced in a globular 

 vessel by the liigh frequency discharge from a 

 Leyden jar system. The vessel in which the 

 discharge was produced contained electrodes 

 which were connected through a galvanometer 

 to a source of E.M.F. of 220 volts. When 

 the discharge passed in the vessel, the gas be- 

 came a good conductor. The conductivity as 

 indicated by the galvanometer was found to 

 depend on the pressure of the gas somewhat. 



That is, when the pressure becomes so low 

 that the white discharge appeared, the con- 

 ductivity increased to near a maximum. It 

 remained nearly constant until at a low pres- 

 sure the discharge disappeared, when the con- 

 ductivity became zero. 



The absorption of energy was measured by 

 placing a hot-wire galvanometer in the circuit 

 leading from the jars to the coil surrounding 

 tlie vessel. The oscillating current passing 

 through this galvanometer and coil can be 

 expressed by 



c A e-i' = cos pt. 



The greater part of the energy is dissipated 

 in heating the gas and the vessel. The en- 

 ergy will be proportional to the square of the 

 current, while the galvanometer reads current 

 direct. Hence 



*°S^ j^ 



' cos picll, 



•2a' -I- 3o' 

 Readings a , , , 



That is: a certain reading is obtained with- 

 out the vessel in the coil. When the dis- 

 charge passes in the vessel, the readings drop 

 back to a smaller value. This drop-back is 

 proportional to the dissipation q in the circuit. 

 The energy absorbed reaches a maximum near 

 the pressure at which the discharge first ap- 

 pears. It steadily decreases and l)ccomes zero 

 again at the pressure at which the discharge 

 disappears. 



A second paper was read by Dr. Charles 

 Lane Poor, on ' The Measurement of Racing 

 Yachts.' 



The measurements discussed in this ])aper 

 are made for the purpose of classifying the 

 yachts and furnish a basis for handicapping 

 them in racing. From such measurements, 

 made of the hull, spars and sails, an expression 

 is found for the ' theoretical speed,' or speed 

 the yacht should make imdor normal condi- 

 tions. While every little detail of hull and 

 rigging contributes its part in producing a 

 fast yacht, yet it is manifestly imiwssible to 

 take account of all such details in finding the 



