1874.] 237 [Hunt. 



by their future efforts, may extend the boundaries of knowl- 

 edge, thus aiding in the work of human progress, while they 

 carry forward to yet further completion, those investigations 

 and discoveries which, in our own day, have given immortal- 

 ity to the names of Humboldt and of Agassiz. 



Dr. T. Sterry Hunt made some remarks on the stratifica- 

 tion of rock-masses. 



The crystalline rocks are commonly divided into stratified and 

 unstratified ; the first being those whose arrangement suggests that 

 they have been formed, like the uncrystalline sedimentary rocks, by 

 the accumulation of matters at the bottom of seas or lake-basins ; and 

 the second those which are supposed to have been erupted or forced 

 out in a more or less liquid state from the inner portions of the earth. 

 These two classes correspond to what the author has designated 

 indigenous and exotic rocks, but a third class must be distinguished, 

 which he has called endogenous rocks, and which appear to have been 

 deposited from solutions, not in open basins, but in fissures at greater 

 or less depths from the surface, and under peculiar conditions of tem- 

 perature and pressure. To these crystalline deposits belong the 

 various veinstones, including many of the so-called granites, espec- 

 ially those containing the rarer mineral species. 



The speaker desired to call attention to the fact that a stratiform 

 or layer-like arrangement of the constituent parts is often met with, 

 both in exotic and endogenous rocks, and cannot be regarded as 

 characteristic of indigenous rocks, nor as a proof of aqueous deposi- 

 tion at the earth's surface. The banded structure in mineral veins 

 parallel to their walls is well known, and was remarkably shown 

 in some granitic veinstones exhibited from Ireland, from Maine and 

 from Nova Scotia. In the latter case, the banded granite, looking 

 like a coarse-grained gneiss, is seen to cut at right angles the strata 

 of a mica-schist. This structure is clearly due to successive deposits 

 from water of crystalline matter on the walls of the veins, and re- 

 sults from a process which, though operating in later times, and in 

 subterranean fissures, was perhaps not very much unlike that which 

 gave rise to the indigenous granitic gneisses. 



