EXAMPLES OF THE EXPLANATION OF LAWS. 577 



or rather by weighing a cycloidal card, and comparing 

 its weight with that of a piece of similar card of known 

 dimensions. 



6. To the foregoing examples from physical science, 

 let us add another from mental. The following is one 

 of the simple laws of mind : Ideas of a pleasurable 

 or painful character form associations more easily and 

 strongly than other ideas, that is, they become asso- 

 ciated after fewer repetitions, and the association is 

 more durable. This is an experimental law, grounded 

 upon the Method of Difference. By deduction from 

 this law, many of the more special laws which experi- 

 ence shows to exist among particular mental pheno- 

 mena may be demonstrated and explained : the ease 

 and rapidity, for instance, with which thoughts con- 

 nected with our passions or our more cherished 

 interests are excited, and the firm hold which the 

 facts relating to them have on our memory; the 

 vivid recollection we retain of minute circumstances 

 which accompanied any object qr event that deeply 

 interested us, and of the times and places in which we 

 have been very happy or very miserable ; the horror 

 with which we view the accidental instrument of any 

 occurrence which shocked us, or the locality where it 

 took place, and the pleasure we derive from any 

 memorial of past enjoyment; all these effects being 

 proportional to the sensibility of the individual mind, 

 and to the consequent intensity of the pain or pleasure 

 from which the association originated. It has been 

 suggested by the able Writer of a biographical sketch 

 of Dr. Priestley, in one of our monthly periodicals, 

 that the same elementary law of oar mental consti- 

 tution, suitably followed out, would explain a variety 



VOL. i. 2 P 



