218 



-body wheeled about, may be had in one second. But, 

 if the velocity of the rotation, and, consequently, the num- 

 ber of sensations, be increased, they cease to be distinct, 

 and a continued luminous circle is formed: but, if an 

 opaque coloured body be thus whirled about, a few more 

 distinct sensations may be discerned. Of auricular sen- 

 sations a far greater number may be distinguished : for 

 our celebrated astronomer, Mr. Herschel, has discovered, 

 that upwards of 160 of them may be discerned in a se- 

 cond of time, before they become confused and undistin- 

 guishable.* In general, where the greatest attention is not 

 bestowed on the succession, particularly on that of visual 

 sensations, the memory of those immediately past is so 

 vigorous and lively, that many of them are confounded 

 with, and appear belonging to, the present time, taken 

 in the strictest sense. It is on this circumstance tliat 

 many of the impositions of jugglers are founded. 



The appai'ent length of time depends wholly on the at- 

 tention paid to its succession ; it appears short, to those 

 whose attention is firmly fixed on one object. For, atten- 

 tion to succession, in such case, is, as much as possible, 

 excluded. It appears still shorter, to those who sleep 

 without dreaming or interruption; as they are not con- 

 scious of any succession, and judge of the length of 

 time, occupied by sleep, only by the sensations usually 

 .associated with rest, and the changes resulting from 



succccssion. 



* See Mr. Watson's Treatise on Time, p. 32. 



