PEEFACE. 



SINCE the publication of Bischof 's ' Lehrbuch der chemischea 

 und physikalischen Geologic ' (1847-54), seldom has any thing 

 excited more sustained interest among geologists than the ques- 

 tion as to the nature and origin of metamorphic rocks. At the 

 Paris Exhibition, in 1878, an International Congress, comprising 

 many eminent geologists, was convoked, one of the main objects 

 of which was to consider the problem of metamorphism. Re- 

 searches having the same purpose in view have been promoted 

 by grants from the Government Scientific Research Fund at 

 the recommendation of the Royal Society, and from the British 

 Association. Some sixteen years past the alleged discovery of 

 the so-called "Eozoon Canadense " gave a marked impetus to the 

 study of metamorphic geology; and of late years microscopic 

 observations on metamorphosed rocks and their component 

 minerals have been sedulously pursued. The result of all this 

 is that a vast body of evidence has been gathered together, 

 throwing much new light on the subject in question. 



Nevertheless, if the latest exposition of rock-metamorphism 

 is to be taken as correctly representing its present state, the 

 subject, it would rather appear, has all along been stagnant) 

 having made no progress since Lyell began to write on it 

 more than forty years ago ! Dr. Ramsay, in his Address lately 

 delivered at Swansea as President of the British Association, 

 declares, without any reservation, that in metamorphic rocks 

 " there is little or no development of new material ;" and he 



