400 M. Keilhau's Theory of Granite and othtr Rocks. 



of the actual phenomena. Meanwhile, it cannot be denied that 

 it is just by such anticipatory expressions, sometimes carried to 

 a great length, that it is now pretty common to describe the 

 geological relations in question. But now to the correction of 

 the fault. It is true that a steep dip is a common phenomenon 

 in the district ; but it is also true that those localities only, 

 where porphyry covers the strata, form a pretty constant ex- 

 ception to this, so that, in all other places where we are some- 

 what near one or other granitic boundary, more or less consi- 

 derable dips will be regularly found. But to observe this is far 

 from enough. Many other extremely important things are still 

 to be determined. If we glance over the geological map, where 

 all the irregular outlines, with their salient and re-enterino- 

 beudings, are of granite masses, and observe that these masses 

 lie sometimes longitudinally, sometimes transversely, so that 

 they cannot be traced to an eruptive fissure running in one par- 

 ticular direction — if all tliis be remarked, then, according to the 

 volcanic theory, there can be no regularity, either in the dip or 

 direction. It may be taken for granted that the supporters of 

 tliat tlieory, after having made their observations in about 

 twenty places, and found nothing in the least corresponding 

 with their ideas, would give up this trivial labour, and that 

 then, as I suppose, they will remain satisfied with this brief 

 conclusion, that the strata here were broken up by lava ; and 

 they naturally ascribe the appearances presented to the intru- 

 sion of abnormal formations, and especially to granite, in com- 

 parison with which, the other penetrating masses are of little or 

 no consequence. As to myself, in consequence of the geognos- 

 tical constitution of my country, I felt inclined to call in ques- 

 tion the eruptive ideas, and I was stimulated to examine, in the 

 most rigid manner, the direction and dip, in order to ascertain, 

 if possible, if there really existed any causal connection between 

 them and the massive formations occurring in the territory. 

 Three of my former pupils have faithfully assisted me in this 

 extensive labour ; and we traversed, two and two together, the 

 districts of the tract of country where the stratified rocks are 

 not interfered with by the massive formations. We followed a 

 strict method, almost as if we had been performing the duties 

 of a land-surveyor ; and, as soon as we had made all our obser. 



