vi TO STUDENTS AND TEACHERS. 



stood. Writings carry with them only to a small extent this sort of license i 

 in a lecture the eye and ear work together. The eye is the only sense that 

 acts in reading ; the memory retains more readily what it receives from 

 oral lessons than what it gets by simple reading. In listening, the impres- 

 sions are more numerous, more vivid, more agreeable, more natural perhaps , 

 but they are less complete, less exact, less pure, less clear than those received 

 from reading : therefore, if one is wrong in listening without reading, he 

 would be equally wrong to read and not listen. These two modes of in- 

 struction mutually assist each other, and are not reciprocally exclusive. If 

 you would profit by them, listen, and retain as much as you can, and then 

 study the subject in those books that treat it best. By reading, you rectify 

 the errors of the ear, and listening clears up what may have been obscuro 

 in reading. If you would clearly understand what you hear, read before or 

 after, or both before and after the lecture what has been published about its 

 subject. 



No one would expect to become a poet or tragedian by simply listening to 

 recitations or witnessing the representations at a theatre. Nor could any 

 one acquire the information necessary to be a painter, by simply walking- 

 through galleries of pictures. He must resort to books and study their con- 

 tents with care and attention. 



In all times, and in all places, all men have felt the necessity of going 

 from spoken to written language. Formerly, pupils drew the lessons of their 

 masters on the leaves of trees, to meditate on them afterwards at leisure. 

 Professors now, very generally, have their respective courses printed, that 

 the student may have the text always at hand for reference and study. 



An individual entering a city for the first time, will make less progress 

 and become less perfectly acquainted with it, if he depend altogether upon 

 his own observation and verbal directions, than one who joins to these means 

 of information, guide books and maps. To become acquainted with anatomy 

 ly merely listening to lectures, or by reading only, or by dissecting alone, 

 unaided either by oral lessons or books, would be the labour of a life time, 

 even if it be possible at all ; but by joining all these means, by listening to 

 lectures, by reading, and by dissection, he will lessen the labour, abbreviate 

 the time to a few years at most, and attain a perfect and exact knowledge 

 of the science. 



To read, to see, to hear, to study, to observe, and to listen are not too 

 many means of acquiring solid information of any physical subject. Who- 

 ever confines himself to one of these means alone, to the exclusion of all 

 the rest, will never acquire complete knowledge of any physical science. 



To study natural history then with entire success, the student should listen 

 to lectures, read and study in books, visit museums and collections ; and in 

 order to join the observation of material things with reading and lectures, 



