396 THE OUTGO OF ENERGY 



the eyes. Let an assistant place on the last 

 phalanx of- the middle and index fingers a small 

 round box containing ten small shot. 



When the subject has formed a clear percep- 

 tion of the weight, let an assistant add or 

 subtract shot, arid record the number of shot cor- 

 responding to the smallest difference in weight 

 perceived by the subject (whose eyes of course 

 should be kept closed). Eepeat the experiment 

 with 20, 30, 40, and 50 shot in the box respec- 

 tively. Determine in each instance the ratio of 

 the number of shot added or subtracted to the 

 number with which each experiment was begun. 



This ratio will be approximately constant. 

 The degree of stimulation necessary to cause the 

 perception of difference always bears the same 

 ratio to the degree of stimulation already applied. 

 Weber's law is less true for very small and very 

 large weights than for those of medium value. 

 It is a general law and holds good for visual 

 judgments, etc. 



After-Sensation of Pressure. Place a rubber 

 band about the head and allow it to remain for 

 several minutes. 



On removing the band, a distinct after-sensa- 

 tion of pressure will be felt. 



Temperature and Pressure. Place on the back 

 of the hand supported on the table a coin the 



