Maclurt^s Letters. 15i) 



own superiority, and to the vast advantages they enjoy, in the 

 simplicity, regularity, and undisturbed state of the stratification 

 of our field of observation. It will give them a proper confi- 

 dence in their own powers, and teach them the real value of 

 those European theories, fabricated in cabinets, originating 

 more out of literature than science, and more indebted to the 

 pen than the hammer, perverting the few accurate observa- 

 tions that have come within the sphere of their knowledge, to 

 suit the arrangement of their circumscribed field, distorting 

 and crowding all observations to suit the model formed by their 

 imaginations and squaring the stratification of the globe, by 

 the imperfect knowledge they have acquired of their own 

 districts. 



Confidence in theories is generally in the exact ratio of 

 ignorance in practice; some mineralogical travellers in Amer- 

 ica do not soar above the level of mineral merchants, or per- 

 haps of the agent of such merchants, who, tempted by the vast 

 number and variety of the cabinet specimens discovered by 

 the industry and science of our young mineralogists, make it 

 their great object to form" such abundant collections of speci- 

 mens, as the unsuspicious communications of our observers 

 may enable them to do — (for the number of our amateurs is 

 very great and they are scattered all over the continent ;) thus 

 they fill the foreign mineral shops with specimens, and their 

 own pockets with money, perhaps laughing in their sleeves, 

 in the mean time, at our credulity, in taking them for men of 

 science, while under the cloak of that name, their only object 

 was a mercantile speculation. 



In sketching some years since, the outlines of our stratifi- 

 cation, in the boundaries or limits of the different classes of 

 rocks,I have no doubt, that I may have committed many errors ; 

 but the sense of our practical geologists is safe from the de- 

 lusion of chimerical cabinet systems, formed by speculation 

 on partial and circumscribed localities. 



I am, perhaps, warranted in thinking, that the mass of 

 geological facts, already collected, and augmenting everyday, 

 puts our students out of the reach of quackery, and of im- 

 aginary theories, and that nothing but well authenticated 

 practical facts can have any weight with them. 



The thirty or forty cases of geological specimens, which I 

 thought necessary to support my sketch of our geology, 

 (now lodged in the collection of the academy of Natural 

 Sciences in Philadelphia,) will, I presume, remain unchang- 



