PEEFACE. 



THE Essays in this volume are some among the con- 

 tributions to KNOWLEDGE (the weekly journal, but 

 also, I trust, to knowledge itself) during the first 

 ten months of its existence. Others by the same- 

 Authors and Mr. Ranyard form f ' Leisure Readings," 

 the fifth volume of the " Knowledge Library Series." 

 The object in all these Essays has been that which 

 the projectors of KNOWLEDGE have had in view, to 

 bring scientific facts before the public in simple but 

 correct words, without perplexing readers, on the one 

 hand, by recondite descriptions or technical terms, 

 and without derogating, on the other hand, from the 

 dignity of science. 



RICHARD A. PROCTOE. 



LONDON, December, 1882. 



