PHYSICAL KNOWLEDGE. 29 



attempting a reply, we must discriminate carefully between 

 the teacher who undertakes the selection, combination, arid 

 presentation of the results, and the person who receives 

 them, when thus presented, as something not sought out by 

 himself, but communicated to him by another To the first, 

 some exact knowledge of the special is indispensably neces- 

 sary ; before proceeding to the generalisation of ideas, he 

 should have wandered long in the domains of the separate 

 sciences, and have himself observed, experimented, and mea- 

 sured. I cannot deny that where positive knowledge is 

 wanting in the reader, general results, which in their mutual 

 connection lend so great a charm to the contemplation of 

 nature, are not susceptible of being always developed with 

 equal clearness ; but, nevertheless, I permit myself the plea- 

 sure of thinking, that in the work which I am preparing, 

 the greater number of the truths presented will admit of 

 being exhibited without the necessity of always reascending 

 to fundamental principles and ideas. The picture of nature 

 thus drawn, even though some part of its outline may be 

 less sharply defined, will still possess truth and beauty, and 

 will still be suited to enrich the intellect, to enlarge the 

 sphere of ideas, and to nourish and vivify the imagina- 

 tion. 



Our scientific literature has been reproached, and perhaps 

 iiot without justice, with not sufficiently separating the gene- 

 ral from the special the view of that already gained, from the 

 long recital of the means which have led to it. This reproach 

 even led the greatest poet of our age ( 15 ) to exclaim with 

 impatience, that " the Germans have the gift of rendering 

 the sciences inaccessible." Whilst the scaffolding stands, 

 it obscures the effect of the finished building. Who can 



