418 



THE GEOLOGIS'T. 



very all this was changed ; and, when it was finally recognized that strata 

 of every age could be distinguished without doubt or ambiguity by their 

 contained fossils, geology became absorbed in Pala3ontology. The 

 mineralogical study of rocks was neglected and despised; the most 

 eminent geological writers were content, in their handbooks, servilely 

 to copy from MaccuUoch or Jameson their mineralogical descriptions ; 

 and voluminous works appeared on various formations without a dij:ect 

 reference to the mineral character of any of their comprising rocks. 



ly. "Within the last two or three years, however, a reaction has com- 

 menced, and the attention of numerous geologists in this country is now 

 directed to the study of various phenomena connected, more or less 

 closely, with the consideration of the mineral and chemical constitution 

 of rocks. On the Continent enormous progress has been made by 

 patient chemical researches, by which an entirely new light has been 

 thrown upon the subject of the genesis of many rocks. The results of 

 the labours of Delesse, Bunsen, Eischof, Charles Deville, Daubree, and 

 many others in France and German}^, and, of late years, those of some 

 of our own countrymen, especially Sorby, now induce us confidently to 

 anticipate that daring a few ensuing years the progress of chemical and 

 mineralogical geology will lead to results not less important and 

 marvellous than those that have followed during past years from the 

 investigations of palceontologists, 



Y. The study of rocks naturally falls into two divisions. The first 

 is purely mineralogical and descriptive, and merely aims at giving a 

 correct description, and forming a comprehensive classification, of the 

 various rocks according to their mineral contents; ascertained, when possi- 

 ble, by inspection with the naked eye or with the lens or microscope, aided 

 by the ordinary mineralogical tests ; or, when the several constituent 

 minerals arc so intimately mixed as to be undistinguishable by these 

 means, then by chemical analysis. This mineralogical and descriptive 

 branch of the science of rocks is of the greatest value to the practical 

 geologist, both for scientific and economical purposes, but is lamentably 

 neglected in England, where gross inaccuracies in the descriptions of the 

 most abundant rocks are of constant occurrence, and committed by men 

 who would shudder at the least error in any paloeontological detail. 



YI. In the second division of the subject we do not regard rocks 

 nccorcling to their mineral constituents, but rather according to tlicir 

 chemical constitution. Our object is not merely to describe and classify 



