INTRODUCTION. xix 



reference to subjects which can be readily understood by children, 

 and illustrations should be selected from objects and operations 

 familiar to them in every-day life." 



In the following pages the object aimed at is to provide a kind 

 of "Playbook," which, in addition to affording the means of 

 amusement, shall also to some extent tend in the direction of that 

 course of mental education advocated by the British Association 

 Committee ; so that whilst the juvenile philosopher finds pastime 

 and entertainment in constructing simple apparatus and preparing 

 elementary experiments, he may at the same time be led to 

 observe correctly what happens, to draw inferences, and make 

 deductions therefrom ; and, by comparing together the results ob- 

 tained in different cases, may gradually acquire some degree of 

 elementary training in the proper exercise of those mental qualities 

 which systematic scientific education chiefly calls forth; and in 

 addition may pick up a variety of pieces of information as to 

 the " why and wherefore " of things connected with the pheno- 

 mena of nature generally, and more particularly with matters of 

 everyday occurrence, especially the various arts and manufac- 

 tures, and the innumerable scientific applications nowadays met 

 with on all sides of everyday life. 



Not being written with a view to aid in "preparing for ex- 

 aminations" nor in accordance with any particular syllabus of 

 requirements, the subject-matter is not arranged in any specially 

 methodical order, but rather in such a way as to connect together 

 somewhat analogous phenomena, quite irrespective of whether 

 they would or would not be juxtaposed in a more systematic text- 

 book ; to aid in elucidating the general principles underlying the 

 observed manifestations and effects, by comparing together the 

 results of various experiments, numerous cross references are 

 inserted, by the use of which many phenomena alluded to in 

 different sections are shown to be related to one another or to 

 have some common cause. Accordingly, although the book is not 

 written specially with the expectation of its being used as a class- 

 book for elementary instruction, it is nevertheless believed to be 

 capable of being to some extent usefully employed in that direc- 



