Sec. 8.] detailed descriptions. 129 



seen near the largest block (Fig. 9). The trap around the various blocks 



Fig. 9. On an island in Nerbudda river, opposite Mundlaisur : a. Granite : 5, Granite 

 passing into coarsely crystalline granite : c. Granite passing into trap ; c*, compact trap. 



often contains large crystals of felspar precisely similar to those in the 

 granite (which is chiefly pegmatite), and some spots are seen in which 

 there is no granite, but still felspar crystals are difi'used. Apparently the 

 granite has in every case been more or less dissolved in the molten trap, 

 and the felspar has again crystallized out upon the trap cooling, the 

 quartz probably combining with the basic minerals of the trap. The 

 smaller fragments of granite were evidently entirely dissolved, while 

 larger masses were only fused and mixed with the trap on their edges. 



It is by no means clear whether the trap occurs in a dyke or in 

 a flow, the small island in which the granite masses occur being some- 

 what isolated. No distinct dyke can be made out, but nevertheless the 

 blocks are not seen out of one general line. This might be caused in 

 a flow, somewhat as lateral moraines are in a glacier, if the lava current 

 passed by rises of metamorphic rock. The trap consists of felspar 

 porphyry and difiers from the distinctly bedded flows in the neighbour- 

 hood, so there is some probability of its being intrusive. Whether 

 dyke or flow, however, is comparatively immaterial, the blocks of granite 

 have evidently been brought up by the one or carried along by the other, 

 and they are certainly not in situ.^ 



* For an instance of blocks of granite being included in a lava stream ejected from 

 a volcano, see Danbeny on volcanoes, p. 337, and quoted by LyeU. 



E ( 291 ) 



