INTRODUCTION TO PART II 159 



upon it. Directions in some form or other must be 

 given the students by the teacher; when spoken, some 

 students do not hear them, others forget them, but 

 the written outline keeps them before all. So great 

 is the advantage of these weekly guides in economizing 

 the teacher's time and strength, and in giving definite- 

 ness and direction to the student's work, that there is 

 in my experience no pedagogic device of greater worth. 

 There is not the slightest objection to them on the 

 score of weakening the student's self-reliance, and 

 when given a proper form they become a great stim- 

 ulus to him. They completely deliver the teacher 

 from that otherwise familiar but awful question, 

 " What do you want me to do next ? ' 



The experiments here given are such as seem to 

 me indispensable. Experiments much easier to try 

 are given in various books, but many of them are on 

 comparatively unimportant topics ; and it is worth 

 while to take some extra trouble to illustrate sub- 

 jects so fundamental as those here recommended. 



The entire course as given in the outlines has been 

 carefully adjusted as to time, and is worked out by 

 my own students in a college year, with four, or some- 

 what more, hours in the laboratory, one demonstra- 

 tion hour, and one lecture a week. If but half, or much 

 less, of this time can be given, the teacher will natu- 

 rally select from the list the more important topics. 



