546 T. H. Holland — Rock-iveathering and Serpentinization. 



submerged since the eruption of the peridotites no general 

 serpentinization has occurred. 



But the area mentioned by Professor Merrill offers positive 

 evidence also in agreement with the facts detailed for India : — The 

 peridotites of western North Carolina lie in a chain of such eruptions 

 whose outcrops occur at irregular, but frequent intervals along a 

 narrow belt, stretching from Tallapoosa County in eastern Central 

 Alabama, on the south-west, to Trenton, New Jersey, on the north- 

 east, whilst fewer outcrops are recorded further northwards in the 

 states of Vermont, New York, Connecticut, Massachusetts, New 

 Hampshire, and Maine. In a paper on the Chromite of North 

 Carolina, Dr. J. H. Pratt,^ referring to this belt of peridotites, says : 

 " In North Carolina and in the more southern portions of this belt 

 the prevailing rock is dunite, while in the northern portion the 

 secondary rocks, serpentine and talc, are prominent." Now, it is 

 in the region of North Carolina that the crystalline hiatus is widest, 

 whilst as the belt is followed in the north-east direction, the Triassic, 

 Cretaceous, and Tertiary sediments are seen to encroach on the 

 crystalline rocks, and to converge to the old Palseozoic boundary of 

 the Appalachians, until, in Maryland and New Jersey, there is fair 

 evidence to show that the crystalline rocks have been submerged 

 more than once since the commencement of Triassic times.' 



As many of these peridotite intrusions are found in contact with 

 crystalline rocks only, their precise geological age is not known. 

 But this and the exact value of such evidence can be discussed with 

 profit only by the geologists possessing the necessary local knowledge. 

 This opportunity might be taken to subpoena the Scandinavian and 

 Canadian geologists, who are familiar with old crystalline land areas. 

 One knows through Brogger^ of the remarkably fresh oli vine-rock 

 of Sbndmore in Norway, which is not apparently near any marine 

 sediments, though suspiciously near the coast. The ophicalcites and 

 serpentines of the old schists would naturally be excluded from this 

 discussion, as they would involve questions of origin far more 

 complicated than that of simple serpentinization. Still, even they 

 are suspiciously associated with limestones. 



Old serpentines are known in the Lake of the Woods and Eainy 

 Lake areas of Canada to be older than the folding of the Keewatins 

 (Lawson) ; with the Cambrian and Cambro-Silurian of the Eastern 

 Townships of Quebec (Ells) ; and with altered volcanic rocks in the 

 lower part of the Carboniferous of the Kamloops region (Dawson). 

 But I can recall no instance of a distinctly eruptive peridotite in the 

 portions of the old Canadian crystalline protaxis which are not 

 covered by marine sediments. The Canadian geologists will be 

 able to tell us whether such exist, and to what degree they have 

 been altered. The crystalline rocks of Canada have also been cut 

 by basic dykes, and it would be interesting to know if the olivine 



1 Trans. Amer. Inst. Mining Engineers, Feb., 1899 ; see also literature therein 

 quoted. 



2 See McGee's Geological Map of the United States, 1884. 



3 Neues Jahrb. f. Min., 1880, ii, pp. 187-192. 



