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PREFACE. 
THE Ten Lectures of which this volume is composed 
were delivered last spring, in St. John's Wood, to a 
large audience of children and their friends, and at 
their conclusion I was asked by many of those present 
to publish them for a child's reading book. 
At first I hesitated, feeling that written words can 
never produce the same effect as viva-voce delivery. 
But the majority of my juvenile hearers were evi- 
dently so deeply interested that I am encouraged to 
think that the present work may be a source of 
pleasure to a wider circle of young people, and at the 
same time awaken in them a love of nature and of 
the study of science. 
The Lectures have been entirely rewritten from 
the short notes used when they were delivered. 
With the exception of the first of the series, none of 
them have any pretensions to originality, their object 
being merely to explain well-known natural facts in 
simple and pleasant language. Throughout the whole 
book I have availed myself freely of the leading 
popular works on science, but have found it im- 
possible to give special references, as nearly all the 
