TO INSTRUCTORS. 



The "Brief Synopsis" of Appendix I. is intended to facilitate 

 the use of this Manual as a recitation-book. Lectures cannot well 

 be wholly dispensed with in the instruction of Natural or Physical 

 Science ; but, with a work so full of illustrations as this, they may, 

 with great advantage, be altogether subordinate to recitations, espe- 

 cially if the latter are accompanied with an exhibition of speci- 

 mens. Through the use of fine type for the details of the Science, 

 the Manual is made to combine in one a small and a large book. 

 The topics presented in the "Synopsis" are, with few exceptions, 

 those of the former ; and they are so prepared that each suggests 

 a question. A cursory perusal of the details in the smaller type is, 

 however, to be advised, as it will aid the student in acquiring precise 

 ideas. Even in scientific schools it may be best that the student 

 first go through the Manual with the Synopsis, and then, in a second 

 course, take up the Palaeontology and Dynamics with greater 

 thoroughness. 



Every Academy or other Institution teaching the Science should 

 have, at least, a small collection of specimens. Even twenty-five 

 dollars will purchase one (of Louis Ssemann, Paris, 45 Eue St. Andre- 

 des-Arts, or of Dr. A. Krantz, at Bonn on the Ehine) containing 

 specimens of nearly all the mineral species mentioned in the 

 Manual, and of the more common kinds of rocks, and another 

 twenty-five dollars, a collection of fossils that would be of great 



