THE IJUILDING OF AN ISLAND. 45 



The special dip of the rocks seen along the piece of road above named 

 that is to sa}', a dip to south or south by east, can be shown to extend over a 

 large part of the northwestern hills, but we soon find that it bv no means extends 

 over all pairts of them ; to the north and east another dip prevails, namely, a 

 dip to east-northeast or points near to that. These latter dips are as prevalent 

 over the northeastern half of the hill-block as southerly dips are prevalent over 

 their southwestern half. It is, moreover, possible, by making suftlcientlv nu- 

 merous observations, to ascertain approximately where the line lies that sepa- 

 rates the two areas of different dips, and to show that it passes through the 

 hills from about west-northwest to east-southeast, as shown on the accompa- 

 nying sketch map.* 



The discovery of the dividing line between these two areas of differing 

 dips is sufficient to show that there is an order of some sort in the arrange- 

 ment of the strata; but it remains to find out how that order is to be inter- 

 preted. What has happened to bring about such an arrangement of these 

 rocks ? 



Upturned edges are found everywhere throughout both areas, but are 

 most striking in the southern area, along the road near Concordia, already 

 mentioned, where the abruptness of the edges is so conspicuous that we natu- 

 rally ask what has become of the parts that must have been removed to show 

 these remarkable edges ? 



It is not difficult to see that, given time enough, the wearing away of a 

 large portion of the strata could be accounted for by the action of rains and 

 the consequent rills and streams passing over the rockv edges, a destruction 

 which, in fact, may be observed to be going on at the present day; but what 

 forms had the strata in earlier times ? Were they by gigantic forces broken 

 off somewhat above the present edges, and if so, what forces broke them off, 

 and what has become of the upper part so broken off ? Or did thev fold over, 

 as their direction seems to hint, towards the north, the top or arch of the fold, 

 in that case, having since been worn away? And if the rocks have been 

 folded over, how can the southerly-dipping rocks be connected by a fold with 

 the more northern rocks, which have a dip almost at right angles to theirs ? 



Had the two dips, as in the diagram (Fig. i8), been at right angles to the 

 line of division which we have been able to lav down between the two areas, 

 the explanation would have been very simple ; the line in question would give 

 the position of an anticlinal axis, from which the rocks slope awa)' on each 

 side, and it would only remain to explain the removal of the vast mass of rocks 

 forming the upper part of the anticlinal curve. 



In such case the whole storv would be shown in a diagram such as that 

 given below (Fig. 19), which represents a cross-section, lying about north- 

 northeast and south-southwest. 



* The reader who wishes to follow up this investigation in detail will find it dealt with in the Notes 

 which follow these Chapters. 



