390 Expedition to the 



the up-turned margin of the whole secondary Formation,* 

 which occupies the plain, and arriving at the primitive, we 

 find these highly inclined strata of sandstone, reposing im- 

 mediately against the granite. We search in vain for any 

 traces of those rocks distinguished by the Wernerians as 

 rocks of the transition period. We also observe an entire 

 deficiency of all those primitive strata which the doctrine of 

 universal formations may have taught us to look for in ap- 

 proaching the granite. 



The sandstone along the base of the mountains, though 



* The word formation appears to have been ordinarily used to sig'nify a 

 series of rocks, formed at the same time, and in the saiiie manner; it is 

 therefore theoretical, and implies a falsehood. Notwithstanding' these ob- 

 jections, it is not easy to dispense with its use. Similar complaints might 

 be made against stratum, bed, vein, and numerous other words, so closely 

 incorporated with the language of geology, that the use of them cannot be 

 avoided. In an attempt to describe <he mineral features of any country, 

 some difficulty arises from the unsettled and progressive condition of the 

 science of geology. A nomenclature constructed upon principles applica- 

 ble to other branches of Natural History, has been extended to this. At- 

 tempts have been made to define classes, orders, genera and S/jecies, of 

 rocks, while it must be acknowledged, that the inventors of systems have 

 hitherto failed to point out such infallible distinctions as exist in the ani- 

 mal and vegetable kingdoms. Among minerals, from one extreme of the 

 series to the other, there is a constant transition of approximating aggre- 

 gates into each other. The particles of inorganic matter, exempt from 

 the influence of those peculiar laws which regulate the forms and charac- 

 ters of living beings, and moving in obedience only to the impulses of at- 

 traction and affinity, arrange themselves together, not always in an inva- 

 riable order, and after a permanent and unalterable type, but are variously 

 intermixed and confounded, as circumstances may have variously influ- 

 enced their aggregation. Definitions hav3 been invented, strictly ap- 

 plicable to particular portions of matter, which may occur under similar 

 circumstances, in remote quarters of the globe. Fragments of granite 

 may be found in the Rocky Mountains of America, which could not be 

 distinguished from the granite of Egypt, such as is seen in our collections. 

 But when we approach the imaginary limits of the artificial divisions erected 

 by the architects of systems, we perceive the fallacy of their distinctions, 

 and definitions. It must be evident to any person familiar with the exa- 

 mination of the rocky materials composing the earth's surface, that be- 

 tween any two of the contiguous artificial divisions, nature has placed no 

 definite and discoverable boundary. Granite must consist essentially of 

 feldspar, quartz, and mica; so must gneiss and mica slate, and between 

 the two former it is often difficult to point out the line which shall be con- 

 sidered as marking the termination of the one, and the commencement of 

 the other. It will, we think, be acknowledged that not one of the names 

 applied to rocks as constituting extensive strata, conveys of itself a definite 

 and satisfactory idea. Hence the necessity in attempting to give a de- 

 tailed account of the rocks of any particular district, to define the names 

 in almost every instance of their applicatioo. 



