Observations on the geology of the United States of America; with some remarks on the effect produced on the nature and fertility of soils, by the decomposition of the different classes of rocks. And an application to the fertility of every state in the Union, in reference to the accompanying geological map ... / By William Maclure.

  • Maclure, William, 1763-1840.
Date:
1817
Catalogue details

Licence: Public Domain Mark

Credit: Observations on the geology of the United States of America; with some remarks on the effect produced on the nature and fertility of soils, by the decomposition of the different classes of rocks. And an application to the fertility of every state in the Union, in reference to the accompanying geological map ... / By William Maclure. Source: Wellcome Collection.

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    dipping the same as the primitive, though at a less angle, the strata running in the same direc- tion; and trom its relative situation, dip, and stratification, bearing no characters of the se- condary, not having been yet found alternating with secondary rocks, it cannot be classed with them, without destroying all order and introdu- cing confusion. To class it with the primitive, would be making the primitive include not only aggregates composed of pieces of different kinds of rocks rounded by attrition, but also limestone with a dull fracture, coloured by organic or other combustible matter, which it loses by being burnt. It would perhaps add to the precision of the classification, if this class was augmented by placing some of the porphyritic and other rocks in it, which are more of an earthy than chrys- talline fracture, but which at present are consi- dered as primitive. It might have been as well if, when giving names to the different classes of rocks, all re- ference to the relative period of their origin or formation had been avoided; and in place of primitive and secondary, some other names had been adopted, taken from the most prominent feature or general property of the class of rocks intended to be designated, such as perhaps chrys- talline in place of primitive—deposition or hori- zontal in place of secondary, &c.; but as those old names are in general use, and consecrated by time and long habit, it is more than proba- ble that the present state of our knowledge does not authorise us to. change them. The adoption of new names, on account of some 8]