PREFACE 

 TO THE FOURTH EDITION 



THIRTEEN years have now elapsed since this work was first 

 published, and in the two intervening editions every care 

 was taken to revise the text and to add information as 

 to new discoveries. The subjects of Molecular Physics, 

 Electro-magnetism, and Botany were all more fully treated, 

 and a chapter was added to the science of the eighteenth 

 century dealing with the experiments of Sauveur and 

 Chladin on musical vibrations. 



In the present edition, besides careful revision, a further 

 and somewhat important change has been made. The 

 recent advances in science had all hitherto been treated 

 together in a final chapter, and were in consequence often 

 overlooked. The latter part of the volume has now been 

 recast, and each branch of science brought up separately 

 to our present knowledge so far as space will allow. 

 Scanty as references to modern discoveries must necessarily 

 be in a small work of this kind, they nevertheless awaken 

 a desire to know more, and I venture to hope that for 

 young students the book is now a fair introduction to the 

 study oi science. 



UPCOTT AVENEL, 



October 1888. 



