50 Prof. J. 1). Dana on some Results oj 



coking of the mineral coal, and probably, on the western out- 

 skirts where the movements were small, the distillation of 

 mineral oil, through the heating of shales or limestones contain- 

 ing carbohydrogen material, and its condensation in cavities 

 among overlying strata, with also some metamorphism to the 

 eastward; while in the making of the Green Mountains there 

 was metamorphism over the eastern, middle, and southern por- 

 tions, and imperfect metamorphism over most of the western 

 side to almost none in some western parts. 



Another example is offered by the Triassico- Jurassic region 

 of the Connecticut valley. The process included the same 

 stages in kind as in the preceding cases. It began in a geosyn- 

 clinal of probably 4000 feet, this much being registered by the 

 thickness of the deposits; but it stopped short of metamorphism, 

 the sandstones being only reddened and partially solidified — and 

 short of plication or crushing, the strata being only tilted in a 

 monoclinal manner 15° to 25°; it ended in numerous great 

 longitudinal fractures as a fiual catastrophe from the subsidence, 

 out of which issued the trap (Dolerite) that now makes Mount 

 Holyoke, Mount Tom, and many other ridges along a range of 

 100 miles*. 



These examples exhibit the characteristics of a large class of 

 mountain-masses or ranges. A geosynclinal accompanied by 

 sedimentary depositions, and ending in a catastrophe of plica- 

 tions and solidiiication, are the essential steps, while metamor- 

 phism and igneous ejections are incidental results. The process 

 is one that produces final stability in the mass and its annexa- 

 tion generally to the more stable part of the continent, though 

 not stable against future oscillations of level of wider range, nor 

 against denudation. 



It is apparent that in such a process of formation elevation 

 by direct uplift of the underlying crust has no necessary place. 

 The attending plications may make elevations on a vast scale; 

 and so also may the shoves upward along the lines of fracture ; 

 and crushing may sometimes add to the effect ; but elevation 

 from an upward movement of the downward-bent crust is only 

 an incidental concomitant, if it occurs at all. 



We perceive thus where the truth lies in Professor LeConte's 

 important principle. It should have in view alone monogenetic 

 mountains, and these only at the time of their making. It will 

 then read (plication and shovings along fractures being made 

 more prominent than crushing) : — 



Plication, shoving along fractures, and crushing are the true 



* This history is precisely that which I have given in my * Manual of 

 Geology/ though without recognizing the parallelism in stages with the 

 history of the Alleghanies. 



