lO DE. THOMAS STERRY HUNT ON THE 



declared that the facts were " not all favorable to the baseless hypothesis which is now 

 carried to extremes." Such an origin of crystalline rocks was denied by the neptunians, 

 who held to the direct crystallization of these rocks from a chaotic watery liquid, for 

 which reason we may conveniently and appropriately call their view the chaotic 

 hypothesis. It is also denied by those who hold these rocks to be of simple igneous origin, 

 the first products of a cooling globe, a view which we may call the endoplutonig 

 hypothesis ; and in part by those who advocate what we shall call the exoplutonic or 

 VOLCANIC hypothesis of their origin. 



We have already noticed at le»gth the chaotic hypothesis, both as originally held by 

 "Werner, and modified by the intervention of internal heat, as taught by Delabeche and 

 by Daubrée, constituting what we may call the thermochaotic hypothesis. It remains 

 to notice first the two plutonic hypotheses just named, and finally to consider the meta- 

 somatic hypothesis, both as applied to rocks consisting of crystalline silicates, and to 

 limestones. 



§ 21. Reasoning, as Naumann has said, from " the great resemblance which gneiss and 

 most of the rocks accompanying it bear to granite and to other eruptive rocks ; the proba- 

 bility that most of these eruptive rocks have been solidified from a state of igneous 

 fluidity ; the almost unavoidable assumption that our planet was originally in the same 

 state, and was only later covered with a solidified crust ; finally the fact that in the primi- 

 tive gueissic series, granite and gneiss are found regularly interstratified with each other," 

 we are led to what we have designated the endoplutouic hypothesis, which is, that the 

 primitive rocks form the " first solidified crust of our planet." Naumann remarks of this, that 

 although it has " not found so many supporters as that of the metamorphic origin of the 

 primitive rocks, the objections against it are probably neither greater nor more numerous 

 than against the latter." Of this hypothesis, he adds that " it leads necessarily to the infer- 

 ence that the succession of the primitive rocks downward corresponds to their age from 

 oldest to youngest, because it was, of course, through a solidification from withou.t inward 

 that the strata in question were formed." Those who would maintain, on the contrary, 

 that the succession of these in age is from below upward, must sirppose, as he explains, 

 that the material of the younger crystalline rocks " has been protruded from the interior, 

 through the earth's crust, in an eruptive form." For these two opposite modes of forma- 

 tion, both essentially plutonic, we may properly adopt the names of endoplutouic, already 

 used above, to desigaate the hypothesis which supposes the rocks to be generated within 

 the first-formed crust ; and exoi^lutouic, for that which conceives them to have been 

 formed outside of the same crust, by eruptive or what are popularly tailed volcanic 

 processes. 



§ 22. The endoplutouic hypothesis has not wanted defenders, among whom are 

 some of the most distinguished names of geology. In 1882, we find Hébert, the eminent 

 professor at the Sorbonne, declaring of the ancient crystalline schists, " these mineral 

 masses appear to be due to a crystallization in place, consequent ui:)on the cooling of the 

 fluid terrestrial globe." " The absence firom these of rolled masses or of detritus of pre-exist- 

 ing rocks" — assumed by him — " indicates that water did not at that time as yet exist in 

 the state of a liqviid mass." This series, including various gneisses, micaceous, hornblendic 

 and chloritic schists, with crystalline limestones, " should form a group clearly distinct 

 from all others. It is anterior to granite, and constitutes a truly primitive series, which is 



