SYNTHETICAL STUDIES AND EXPERIMENTS 

 ON METAMORPHISM 



AND ON THE FORMATION OF CRYSTALLINE ROCKS.* 



By M. DAUBREE. 



TRANSLATED BY T. EGLESTON, FOE THE SMITHSONIAN INSTITUTION. 



INTRODUCTION. 



In varietate unitas (Leibnitz ) 



One of the first and most important problems which geology has 

 been called upon to solve is to determine what, in the formation of 

 the solid crust of the globe, is the part to be assigned to aqueous and 

 that which ought, to be attributed to igneous action. The question, 

 although it has been a long time under discussion, has not yet been 

 definitely settled ; it has even been complicated, since, in studying 

 more rigorously the different strata, there have everywhere been 

 found those which unmistakably exhibit evidence of a double origin. 

 Was it at the time of their formation that these ambiguous strata 

 acquired their double characteristics, or was one of these character- 

 istics acquired after the other, and, in the latter case, how can such 

 a succession of effects be accounted for ? Such are the subjects, the 

 study of which constitutes, in its greatest generality, that part of 

 geology which has been called metamorpliism. 



When the influences which the interior regions of the globe exer- 

 cise on the surface show themselves by daily phenomena, such as hot 

 springs, eruptions of volcanoes, earthquakes, or by effects of which 

 man has not been the witness, but of which he finds stupendous 

 traces, such as the eruption of rocks and the upheaving of mountain 

 chains, it is a subject full of interest, and in which every one is ready 

 to engage. But when these influences have produced only slow 

 modifications invisible, inaccessible to direct observation from the 

 depth at which they have taken place, and are without doubt still 

 going on, it is easily conceived that they excite incomparably less 

 interest, and, moreover, that they present peculiar difficulties of in- 

 vestigation. If, however^ we consider that these great transforma- 

 tions were carried on over a large part of the earth's crust, and that, 

 according to all probability, their importance increases from the 



'*■ Annalea des Mines. 6 series, vol. 16, pp. 155 and 393. 



