INDUSTRIAL GEOLOGY. 147 



Afterwards the ridge or apex of the fold has been worn off by the never ceasing 

 action of the elements. Tlius we gain access to the very oldest rocks, and may 

 gather the shells of the old, old seas as easily as we can gather the shells on the 

 shores of our present oceans. Moreover, as the edges of the rock layers are 

 exposed to view by these cosmical foldings and flexures, we can measure the 

 thickness of the rocks as easily as we can pace off the plow land in the pas- 

 ture or stubble field on our farms. The great upl if tings which have made 

 moinitains in all parts of the world were either the cause of great heat, or else 

 caused by great heat. The former is doul)tless true, and this great heat, as 

 alrea/ly suggested, has been the great economist that has hunted out the small 

 mineral panicles and stored tlietn in the mines. Hence we need never expect 

 to find any considerable amount of the precious metals in the later formed 

 rocks, except in or near great mountain ranges. 



The geologist knows tliat it is as impossible to find gold, silver, and copper in 

 such a region as our Lower Peninsula of Michigan as it is to raise wheat in an 

 undrained black ash swamp, in company with flags and sedges, or to raise good 

 Shorthorns in meager pastures, or on stinted rations. It is an interesting fact 

 that all the truths gleaned from a close study of these folded rocks in all parts 

 of the world are in perfect harmony, and in as perfect accord, with the truths 

 gleaned from a study of the same groups of rocks in such grand canyons as 

 that of the Colorado 



Again, we have already noticed that our continents have been built up around', 

 some old time nucleus as around the American V; or nuclei, as about the many- 

 old European islands. As the borders were constantly extended, the continent 

 was as constantly raised, and so as the ages passed on more and more of the 

 continents were raised permanently above the encroachments of the ocean 

 waves. Thus, as we come south from the southern shore of Lake Superior,, 

 we traverse later and later formed rocks. As already stated the oldest vegeta- 

 bles were wholly marine and consisted entirely of sea weeds. Naw in all rocks 

 areas that were raised permanently above the ocean in this time will show irt 

 its list of fossils only such plant remains. It is a very significant fact that the 

 successive rock areas from north to south in the Upper Peninsula and northern 

 half of the Lower Peninsula of our State, as also corresponding areas in New 

 York from north to south across the State, show a succession of life forms 

 in exact agreement with that discovered in passing from the highest to the 

 lowest rocks of the river gorge, or in passing from the centre to the outside of 

 a flexture in the mountain upheavals. All these stories of the past life and 

 history of the world are entirely consistent the one with the other, and prove 

 that Geology is treading on solid ground And thus it is, that though storming^ 

 some of the oldest and most trusted views of the earth and creation, it has 

 gained its point and won universal confidence. 



There are three well-marked times in the earth's history as revealed by geo- 

 logical research. First, that when the life was very unlike that of to-day, ancient 

 life time. In that time there were no insects, no bright, flowering plants; the 

 fishes were very old fashion in structure and appearance, and there were no birds 

 and mammals — the highest life being some very curious reptiles, very different 

 from those of to-day. The second time was quite different from the first, and 

 yet quite unlike that of to-day. We call it the middle life time. Though in this 

 time all the classes of animal life which are known to-day were in existence. 

 Yet the mammals and birds were very few, and very different from those now 

 known to us. The principal life at this time was reptilian. And so this 

 middle life time is known as the " Age of Reptiles." These huge reptileS;^ 



