276 B. KOTÖ. 



and solidity. It would be superfluous to cite every occurrence of the 

 dykes, since they are met with all the way through and in any part of 

 this region, like Jacks at every street corner. A large series of ex- 

 posures of the dykes under their least equivocal and most characteristic 

 conditions of occurrence may be studied on the ascent from Nogami 

 (Tamano-yu cold bath) to Chikenjö, Naraha göri, for a distance of 8 

 km. This profile is very instructive, as there are found in it the often- 

 mentioned two types ol granite, one penetrating the other, and both 

 passing imperceptibly into gneissose modifications, to which the name 

 " Iwaki gneiss " has been already given. Through these granites, 

 the aplitic, pegmatophyritic^ dykes, the granophyre of Rosenbusch, make 

 their way usually at low angles, and strike with the main axis 

 (N 10 E) of the mountain. 



These in turn are cut at very steep angles by a number of diorite- 

 porphjrite dykes ^ Since the filling up of the red dykes (Peg.), the 

 country-rocks have undergone considerable tectonic disturbances to 

 which is due the formation of parallel fissures (Fig. 2, PI. XXIV). 

 Different parts have then been shifted one after another, causing a 

 continuous band of the dykes to appear like a set of stairs, and some 

 of these clefts have been subsequently filled up with the igneous 

 magma, which we now find in the shape of the black diorite-por- 

 phyrite dykes, as may be clearly understood from Figs. 2 and 3, PI. 

 XXIV. From what has been said, there is not the slightest doubt 

 as to the younger age of the diorite-porphyrite, and its formation 

 may perhaps have been at the time, when the crust in this quarter 

 had suffered the last orogenetic movement, in which state it has re- 



1 K. A. Lossen, Vergleichende Studien über die Gesteine des Spiemonts und des Bosenbergs bei 

 St. Weiideliind verwandte benachbarte Eruptivtypen'aus der Zeit des Rotld legenden, Jahrb. d. Königl. 

 preuss. geol. Landesanstalt für 1889, p. 270. 



2 I wish to substitute the word diorite-porphyrite for lamprophyre in Figs. 2 and 3, 

 PI, XXIV. 



