TOUCH 103 



Or, 



Put one hand into water of 20 C. It will feel cold. 

 Now keep the hand in water of 10 C. for one minute and 

 again put it into the water of 20 C. It now feels warm. 



7. Effect of temperature on estimation of weight. 

 Place two metal discs of equal size and weight, one cold, 

 the other warm, on corresponding fingers of the hand; 

 the cold one will feel the heavier. Place both on the 

 forehead, and estimate the relative weights. 



8. Estimation of weight with and without the aid of the 

 sense of movement (muscular sense). A sits with hand out- 

 stretched at a table and with eyes shut. B has metal discs of equal size 

 of 10, 11, 12, 13, 14, 15 grams. He takes 10 grams and 13 grams, and 

 placing first one and then the other in the palm of A* 8 hand, writes 

 down which, if either, A feels to be the heavier. If A is wrong 

 3 times out of 4, then 10 and 15 grams are compared; if A is right 

 3 times out of 4, the 10 and 12 grams are taken, and so on. Having 

 determined approximately the difference which can be distinguished 

 in light weights, heavier weights are taken, viz. 300, 330, 360, 390, 

 420, 450 grams, and the power of distinguishing these is tested in 

 the same way. These weights should be tin cans with handles, of 

 equal size, 6 to 8 cm. in diameter, the weight being made up with 

 shot. 



If with the lighter weights 10 and 12 grams could be distinguished, 

 but not 10 and 11, then with the heavier weights, probably 300 and 

 360 will be distinguished, but not 300 and 330. 



B now gives to A the 300 gram tin, and the tin just below the 

 threshold for the pressure sense; A takes them one in each hand, 

 and lifts them up and down, and changes them from one hand to 

 the other. He 'will probably then be able to detect a difference he 

 was previously unable to detect. 



These experiments require some practice ; it may be found that 

 a sense of difference of weight is distinct at one moment, and dis- 

 appears the next. 



