100 PROCEEDINGS OF THE AMERICAN ACADEMY. 



from its seat after the contact by the observer, tJm average person can 

 surely make a contact as short as a thirtieth of a second, and some can 

 always do better than this. Table II shows records of fair contacts 

 obtained with a thimble and block. While the lengths of the shorter 

 contacts of the average jjerson seem to be rather less — when made in 

 this manner — than one two hundredth of a second, three of the persons 

 (F, 0, P) who made trial of the apparatus could surely make contacts 

 the average lengths of which were only about one three hundredth 

 of a second. 



The Jefferson Laboratort, 

 Cambridge, Mass. 



