4 J. A. PHILLIPS OK CONCRETIOTfART PATCHES AND 



butternut, more especially when stripped of its epicarp. No wonder 



they should be called ' petrified butternuts ' If a specimen, 



somewhat flattened, be placed on its edge, and a moderately sharp 

 blow be given to it with a hammer, concavo-convex scales will be 

 chipped off even to the centre. They are composed of layers of 

 mica with granular quartz, and probably some felspar interposed. 

 The structure is evidently concretionary ; yet, as already intimated, 

 one can hardly avoid the suspicion that something has been ab- 

 stracted from some of them, causing a shrinkage." 



At page 721 of the same volume, the Rev. S. Hall remarks : 

 — " These singular nodules seem to be imbedded in the granite 

 mass ' like plums in a pudding.' They extend only a short distance 

 from the place where first found in Stanstead. From that place to 

 Craftsbury the granite exhibits no unusual appearance. At the 

 south village in the latter town is an immense bed of nodular 

 granite, some of which seems to be composed almost entirely of 

 nodules slightly cemented by grains of mica and quartz. Other 

 parts of the rock are very solid, and not inclined to decomposition 

 more than other granite." 



In a paper " On the Metamorphic Origin of certain Granitoid Rocks 

 and Granites in the Southern Uplands of Scotland " *, Mr. J. Geikie, 

 P.R.S., describes " nests " of altered rock which occur in some of 

 the grey granites of that district. These, he says, often exhibit 

 distinct traces of lamination ; and their most usual character is that 

 of an exceedingly fine-grained mica-schist, the dark or almost black 

 shade being due to the abundance of mica. They are very irregular 

 in shape, and by no means confined to those portions of the rock 

 which abut upon the outlying bedded or aqueous strata, but are, oh 

 the contrary, scattered indiscriminately throughout the granite. 

 He subsequently proceeds to account for the presence of these nests, 

 and states that they " either represent such little detached por- 

 tions of shale as are of common occurrence in the Lower Silurian 

 greywackes, or they may be remnants of thin bands or beds of 

 shale that interleaved the original strata. Those who deny the 

 metamorphic origin of granite will probably suggest that the ' nests ' 

 of altered rock may have been caught up by the granite during 

 its progress through the strata that envelope it. Rut if this had 

 been the case, we should certainly expect to find the ' nests ' not 

 only more abundant near the junction of the granite with the 

 stratified rocks, but indeed almost, if not exclusively, confined to that 

 area. They are not more characteristic, however, of one portion of 

 the granite than of another, but, as already remarked, are scattered 

 indiscriminately throughout. I am therefore forced to conclude 

 that the crystalline rocks described above have resulted from the 

 alteration m situ of certain bedded deposits. The occurrence of the 

 * nests ' cannot be accounted for on any other theory." 



None of the published descriptions of these concretions or enclosures 

 in granites appear to have resulted from investigations founded 

 either upon chemical analysis or upon a microscopical examination 

 * Geol. Mag. vol. iii. p. 533. 



