eotlich.] WIND EIVEE EANGE AND EASTWAED EESUME. 93 



Enough may be said, however, to indicate which groups appearing in 

 other'ehapters pertain to the subject under discussion. From what we 

 haTe observed, we are enabled to say that at the earliest geological 

 periods a narrow range existed, trending approximately E. 50° S. 

 Against the northeastern side four distinct types of sediment were de- 

 posited. That this occurred at long intervals of time, during a period 

 of more or less disturbance of niveau, is evident from the horizontal pro- 

 jection that we can assume for these groups. Such assumption is based 

 upon the study of the series as it now appears — metamorphosed. Apply- 

 ing lifhological nomenclature in order to make clear what is meant, we 

 may say: The Prozoic granite is the remnant of the original range; 

 against this were deposited the old metalliferous schists; granite com- 

 posing the main chain followed; this was succeeded by a narrow band 

 of schists; and the fourth or last group is represented by the younger 

 granites. In case we make an attempt to indicate the original, unchanged 

 condition of these rocks, we may regard them as representing siliceous 

 shales (schists) and more or less argillaceous sandstones (granites). As 

 the earth is but a body "buried beneath its own ruins," we cannot expect 

 to find aught but what is contained in the original crust. Schists and 

 granites or siliceous shales and sandstones, therefore, are essentially 

 the same thing, varying only in the percentages of component parts. It 

 appears that the lowest Silurian strata were deposited before the 

 thorough metamorphosis of the entire mass took place, unless, indeed, 

 we account for the change in the sandstones by assuming a generation 

 of heat during the period of mountain elevation. 



In these very earliest deposits we observe an "overlapping" of the 

 groups. The metalliferous schists are soon hidden from sight by the 

 preponderance of the main chain granite. Eventually this, as well as the 

 younger schists and granites, disappears at another point. This is due 

 probably to pinching out of the groups in certain directions rather than 

 to a lateral inequality in the propelling force which caused the elevation 

 of the mountains. If the latter cause had resulted in the production of 

 this phenomenon, we would find it accompanied by others which we now 

 do not observe. 



Sedimentary formations reach an ample development in this region, 

 considering the disadvantageous locality at which they were deposited. 

 We had at the time of the Silurian, for instance, a more or less elevated 

 ridge, sloping toward the northeast. So far as our observations enable 

 us to determine, we find that the influx of waters came from that direc- 

 tion for a very long period of time. While elsewhere the waters could 

 attain great depths, they were here necessarily shallow, and the amount 

 of material deposited within them must stand in proportion. Thus we 

 find that a number of formations and groups, greatly amplified to the 

 north and northeast, have had but little opportunity to reach any exten- 

 sive vertical development in the vicinity of the Prozoic range. Changes 

 of niveau, which took place probably during loug periods of time, per- 

 mitted some of the younger groups to reach proportionately great thick- 

 nesses. 



Of the Silurian formation we have representatives of two groups. 

 Both of them are characteristic, and are very frequently found in the 

 same relative position throughout the Eocky Mountains. The Carbon- 

 iferous formation is well represented by the two lower groups, which can 

 generally be distinguished. It is with some reluctance that I regard the 

 series of strata above the blue limestones as Permian. Usually this 

 formation carries some typical fossils, but in this instance none were 

 found. A decided similarity of the rocks and the unequivocal position 



