Mikroskopische Physiographie der petrographisch wichtigen Mineralien ein Hülfsbuch, bei mikroskopischen Gesteinstudien

Abstract

SINCE we last called attention to this subject in the columns of NATURE it has been making steady progress, chiefly among our German, that is, of course, German-speaking, brethren of the hammer and lens. The various serials which treat of Geology and Mineralogy bear witness to this progress, and to the wonderful activity of some of the workers, such as our good friends Zirkel and Tschermak, to whom it is so largely due. And now here comes a goodly octavo of some four hundred pages as a further contribution to our knowledge, and a fresh proof of the strong hold which the microscopic study of minerals and rocks has taken of the German geognostical mind. This activity need not be matter for wonder when one considers the chaos into which matters petrographical had got even in Germany. Those who studied rocks in that country had become a sort of bound thralls to chemists and chemical analysis. They dared not trust their eyes to discriminate the differences of species and varieties. The specimens must be handed over to the laboratory, and on the judgment thence obtained depended the names by which the compounds should be known thenceforward throughout Christendom. By this means, as the composition of a rock often differs considerably in different, and even in closely-adjoining, parts—variations resulting partly from original discrepancies, and partly from internal changes due to the subsequent infiltration of water or other metamorphic influences— it was not difficult to make out half-a-dozen distinct varieties of rock from the same mass and even from the same quarry. And so analysis of rocks grew and multiplied, chemists became more and more nice in their discrimination of the veriest fractions of a per cent., petrography seemed in a fair way of being annexed as a dependent province of chemistry, and the petrographers, who ought to have been geologists, and to have set themselves strenuously to find out what had been the history of the rocks as parts of the architecture of the globe, came gradually to accustom themselves to the notion that, after all, it was really true that rocks were merely so many chemical compounds to be analysed and labelled accordingly.

Mikroskopische Physiographie der petrographisch wichtigen Mineralien ein Hülfsbuch, bei mikroskopischen Gesteinstudien.

H. Rosenbusch. With 102 woodcuts and ten coloured plates. (Stuttgart.)