418 
THE GEOLOGtST. 
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 Palajontology. 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 direct 
reference to the mineral character of any of their comprising rocks, 
IV. "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, Bischof, Charles Deville, Daubree, and 
many others in France and Germany, and, of late years, those of some 
of our own countrymen, especially Sorby, now induce us confidently to 
anticipate that during 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 pala}ontologist3. 
V. 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 are 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 palreontological detail. 
VI. In the second division of the subject we do not regard rocks 
according to their mineral constituents, but rather according to their 
chemical constitution. Our object is not merely to describe and classify 
