No. 2.] DANA — SOME POINTS IN LITHOLOGY. 87 



(4.) The sedimentary beds ichich have been converted into crys- 

 talline rocks were often originally massive. — This is the condition 

 of most conglomerates, and often of coarse sandstones. In such 

 cases there would be no bedding to obliterate ; and the production 

 of a massive rock would be a natural result of the metamorphism, 

 whether the heat attending it were great or small. Part of the 

 metamorphic granite of the world may therefore never have been 

 in a pasty state ; and so also part of the metamorphic hornblende 

 rocks ; some metamorphic felsy te beds, certainly those that are of 

 conglomerate origin, were originally massive. 



There is hence reason enough for neglecting the distinction of 

 massive and schistose in drawing out a system or classification of 

 rocks, and for making the question of origin in the case of either 

 kind, the massive no less than the schistose, a subject for careful 

 investigation. 



9. Metamorphic or Eruptive. — The question whether a crystal- 

 line rock is metamorphic and in place, or eruptive, is of the high- 

 est geological interest ; for it is a question as to origin. At the 

 same time, no subject, if we exclude the part of metamorphism 

 relating to the obviously schistose rocks, is in so unsatisfactory a 

 state. With some authors, as above intimated^ the question so 

 far as it relates to massive crystalline rock is not an open one. 

 On the other hand, when investigation has taken place, opposite 

 opinions have generally been reached. The remedy of this is to 

 be found in more thorough study from a wider basis of facts. 



Were the question in all cases rightly decided, lithology would 

 be able to study and compare the two series, and give greater 

 completeness and higher geological value to the descriptions of 

 rocks. Applying different names to the like rocks in the two 

 series is not necessary, unless there is some strong geological reason 

 in favor of it; for when a rock occurs both metamorphic and 

 eruptive the fact is best exhibited if that rock has but one name. 



The writer has proposed to distinguish the metamorphic under 

 any kind of rock by adding to the name the prefix mtta ; for 

 example, dioryte for the eruptive and mctadioryte for the meta- 

 morphic part. But meta is here used simply as an abbreviation 

 of the word metamorphic, not to indicate a difference of kind in 

 the rock. 



Conclusion. 



The principal points with regard to rocks which have been 

 brought out in this paper, are the following. 



