CONTRIVANCE. 87 



relations to each other, just as if one were moving 

 them about by mechanical force, and yet they pre- 

 serve their identity, or are the very same parties 

 amid all their changes of relation, just as the mind 

 itself remains the same amid all its changes of 

 thought. 



This changing of the relations of subjects of 

 thought, to which we give the name of " invention" 

 or " contrivance," is very valuable. It is done in 

 very little time, and with no labour, for there is no 

 weight to be moved, and no resistance to be over- 

 come. A skilful architect will, in his own mind, 

 rear a palace, before a brickmaker can mould and 

 burn a single brick, a mason fetch a stone from the 

 quarry, or a woodman fell a tree ; and he will feel 

 none of the fatigue and exhaustion which they feel. 

 We are, indeed, accustomed to say that the mind is 

 fatigued ; and when we long continue thinking on 

 the same subjects, especially if there is any thing 

 dispiriting in them, we do feel a sort of languor, and 

 pass into a revery, or dreamy state, in which we not 

 only lose the command of our bodies, as we do du- 

 ring slumber, but in the end lose the memory of our 

 thoughts, just as we do in profound sleep, during 

 which we have no dreams. Everybody must recol- 

 lect instances of having thought upon subjects till 

 the memory of all the particulars was gone ; and, 

 when an author writes an original book upon any 

 subject that requires close and profound thinking", 

 the chance is that he shall know less of what is in 

 the book after he has just finished the writing of it, 

 than an intelligent reader after he has- glanced it 

 over. " Don't ask me about that, for I have written 

 upon it," was an habitual saying with a veteran both 

 in science and literature ; and Abernethy's constant 

 referring of his patients to " My book" had phi- 

 losophy in it, whether he understood that philosophy 

 or not; 



This fact, that we not only can, but actually and 

 D 



