PREFACE TO THIRD EDITION. 



This might with propriety be called the fourth edition the main idea 

 of the work having been embodied in a pamphlet under the same title, 

 published in 1873. but long since forgotten. The successive editions 

 have reached their present form by accretion, rather than by develop- 

 ment; like Topsey.the book has "growed," rather than been ' brought 

 up. and just as that young lady exhibited numerous traits which were 

 inconsistent with a proper training, so this book shows patch-work and 

 inequalities which do not add either to its value or its attractiveness. 



Of all this the author is fully conscious, and if he could possibly have 

 secured the necessary leisure he would gladly have rewritten the entire 

 volume. But pressing, or rather imperative calls upon his time, have 

 prevented this, and he has, therefore, been compelled to feel satisfied 

 with such general revision and additions as were necessary to bring the 

 work up to the present state of our knowledge. 



The book is still intended for beginners and has changed nothing of 

 its elementary character. It is true that we have inserted a few pages 

 relating to the higher class of objectives, and the accessories used with 

 them, but those who do not possess such apparatus can easily skip 

 these passages. 



That it is suited to the purpose for .which it was intended, we have 

 evidence, not only in the extended sale which it has secured, but in 

 the fact that it has been adopted as an auxiliary text-book in several 

 of our schools and colleges. 



Neio York, January, 1881. 



PREFACE TO SECOND EDITION. 



The fact that an unusually large edition of this work has been sold in 

 a comparatively short period, is, to the author, evidence that such a 

 work was needed, and that the present volume has, to a certain extent, 

 supplied the want. In the present edition, therefore, he has endeavored 

 to introduce several important improvements, while at the same time 

 .the elementary character of the work remains unaltered. With a few 

 very slight and unimportant exceptions, the entire matter of the former 

 edition has been incorporated in the present, and in addition several 

 important subjects, particularly th chapter on objectives, have been 

 greatly enlarged. 



