INTRODUCTION 5 



devoted to it. First of all in time was the Text-book, 

 the fount of all knowledge, descended to us from early 

 times. The introduction of direct inductive study of 

 facts and phenomena in the laboratory led, if not to the 

 abandonment of the Text-book, at least to its temporary 

 eclipse ; and there rose to prominence the Laboratory 

 Manuals, which were books of directions to enable the 

 student economically to work out the more important 

 truths for himself. But laboratory study alone, neces- 

 sarily confined to a few types, has been found to give 

 too disconnected a view of the Science, and the Text- 

 book for supplementary reading is coming again into 

 favor ; and in some recent books we see an attempt to 

 combine Laboratory Manual and Text-book. The Labo- 

 ratory Manuals, also, have not proved altogether satis- 

 factory, for they necessarily call for definite materials, 

 which oftener than not are wanting when most needed ; 

 and, moreover, a good teacher will not submit to the re- 

 straint they impose upon him, especially in matters of 

 detail, when they are placed in the hands of his students. 

 To meet these difficulties the later books either give an 

 excessive abundance of exercises, far more than can be 

 accomplished in the assigned time, hence allowing a 

 considerable choice, or else they are addressed less to 

 the pupils than to the teacher, for whose benefit many 

 pages of advice are added. This tendency to aim at 

 influencing the teacher directly, to educate and advise 

 him while leaving him free in his choice of methods 



