206 ANNUAL OF SCIENTIFIC DISCOVERY. 



produced by the elevation of mountain chains. But, as a matter of fact, 

 every mountain chain can be shown to be accompanied by corrugated strata 

 and faults, and sometimes by cleavage, and even, perhaps, by systems of 

 joints, in such a way as to show that all these structures were produced by 

 the elevation of the mountain chain, or, rather, that that elevation and ail 

 the other phenomena were the simultaneous results of the same disturbing 

 action. The influence of this action may sometimes be traced to consider- 

 able distances into the lower lands on each side of the mountain chain, gradu- 

 ally fading away as we recede from it, so as to show that the mountain 

 chain was raised over the line of greatest intensity and largest endurance of 

 a comparatively widely spread disturbing force, which, nevertheless, was 

 limited to a certain part of the crust of the globe. 



It appears to me, then, that, to be strictly consistent, Sir Henry should 

 refer the elevation of mountain chains themselves to the slow and gradual 

 shifting of the earth's axis and its protuberant equatorial mass; but then, in 

 that case, where are we to seek for the cause of this shifting? 



The views of Sir Hem-y James have also called forth the Astronomer Royal 

 of Great Britain, Professor Airy, in an article, in which, while admitting the 

 accuracy of the principle invoked by Colonel James, he doubts the adequacy 

 of the cause, in magnitude, to explain the supposed effect. Professor Hen- 

 nesey, of Dublin, also publishes an article in which he supports the views of 

 Professor Airy. 



ON THE GRADUAL PASSAGE OF THE DEVONIAN SYSTEM INTO THE 



CARBONIFEROUS. 



The following is an abstract of some remarks made before the Boston 

 Society of Natural History, by Professor W. B. Rogers, on the occasion of 

 the presentation of a paper by Mr. C. A. White, showing the gradual passage 

 of a Devonian into a Carboniferous fauna, in the rocks of these two systems 

 in the State of Iowa : 



Professor Rogers considered such a gradational -change, or such a mingling 

 of races in successive formations, as but the natural result of the accumula- 

 tion of the strata during a long period of comparative repose. He believed 

 that the abrupt transitions so often observed in passing from one geological 

 formation to another were not, as some maintain, an essential feature in the 

 life-history of our earth, but were the memorials of the disturbing and 

 destro.ying agencies to which its living races had been successively exposed. 

 These hostile influences have at no time been of equal intensity over widely 

 extended areas, but, varying from region to region, have in some places 

 arrested only in part the stream of living descent; thus substituting for the 

 abrupt transition which marks the successive faunaj of one district the 

 gentle gradations and intermingling of forms presented by the correspond- 

 ing deposits of another. 



Referring even to the limits of the great paleozoic divisions, so often 

 defined by sharp lines of separation, observation has shown that in some 

 localities the transition is so gradual as to present no greater amount of 

 change in fossil forms than occurs in passing from one subordinate forma- 

 tion to the next. Hence we find that the ablest European geologists are not 

 agreed as to the line of separation between the Silurian and Devonian, or 

 between the latter and the Carboniferous deposits of some of their best- 

 known districts; while recent observations in this country and abroad have 



