APPENDIX. 483 



though even these things can never he delineated 

 with truth or vigour, without a knowledge of those 

 principles of art which regulate the distribution of 

 light and shade. Lastly, the geologist should he ac- 

 quainted with military drawing; since, to this will he 

 often be as much indebted as his readers, while thus 

 also he will be able to construct the most essential 

 parts of his own maps, or to correct the deficiencies 

 of those on which he must depend. 



Finally, let the student recollect, that he must bring 

 to a task of no small difficulty, acuteness, patience, 

 caution, and industry ; and, that acquainted with all 

 theories, it must be as their master, not as their slave. 

 Thus only will he be enabled to profit, alike, by their 

 excellencies and their defects, by the truths and the 

 errors that are found in all. Where he ought not to 

 follow, he will know why he should dissent : but if, 

 in detecting a false generalization, he removes one of 

 the greatest impediments to the progress of science, 

 let him, in generalizing his own observations, be 

 guided by a feeling more severe to himself than to 

 others. Nor let him forget, that the pleasure or pride 

 which he may feel in supporting a system or a sect, 

 can, ultimately, but terminate in neglect or disgrace. 

 In Science, as in Morals, equally, there is one guide, 

 and one rule : to the wise and the good, there is a 

 common pursuit: one word comprises all; and let the 

 last word that falls from this pen, be, TRUTH. 



FINIS. 



