FOSSILS UNDER GRANITE. 487 



if it formed the upper part of the deposit. The Canada geologists, we believe, have been 

 in the habit of regarding the calciferous schist as of the age of the Niagara group of New 

 York. 



Under granite we shall give additional facts respecting this interesting spot. 



Origin. 



Clay slate often passes by insensible gradations into mica schist, and no dividing line 

 can be drawn between them. Hence we have one of the sources whence mica schist may 

 originate. A comparison of their composition shows that in many cases, but not in all, 

 such a conversion is possible. Sometimes, in consequence of a deficiency of certain in- 

 gredients, a rock will be found intermediate between the two. 



How much of the pure mica schist of Vermont has been derived from clay slate, it is 

 impossible to say. The principal range of mica schist is the calciferous, and clay slate 

 shows itself along both borders of this, often in connection with that which is not calcare- 

 ous. Probably this may generally have been metamorphosed clay slate. Indeed where 

 the two rocks pass insensibly into each other, we cannot doubt that such was the case. 

 Mica schist, however, may be derived from any rock that is silicious and contains the in- 

 gredients requisite for the production of mica. We know that in some instances it has 

 been derived from chlorite schist and green stone, and some sandstones scarcely require 

 much change to become mica schist. We have also shown how, by a process partly 

 mechanical, and partly chemical, even conglomerate may become mica schist. 



What we have called calciferous mica schist exhibits some interesting phases of meta- 

 morphism. A considerable part of it would be better described by calling it limestone 

 with intercalated beds of schist. This is especially true as we approach the northern parts 

 of the State. In Canada, Mr. Hunt describes it as belonging to the upper Silurian, some- 

 times white and crystalline, with " the characteristic fossils of the Niagara group." In 

 Vermont, however, we have never found any fossils and the rock "soon assumes a dark, 

 rough appearance, with projecting masses of quartz and mica schist so obscuring the 

 characters that probably few of the inhabitants suspect the rock to be limestone. The 

 characters become still more obscure as we go southerly, until near Ascutney it is almost 

 entirely changed into, or replaced by, gneiss, as our geological map shows. This rock 

 continues diminishing in width almost to the south line of the State, where the calciferous 

 schist regains considerable width and passes across Massachusetts, losing a good deal of 

 the limestone towards the south part of the State, and becoming more distinctly mica 

 schist. How far it extends into Connecticut we are unable to say ; but it runs far to the 

 east of the crest of the Hoosac Mountain, and has no connection with the micaceous lime- 

 stones of western Connecticut, which are probably of Eolian age. It was not till a 

 few years ago that any persons in Massachusetts imagined that this unsightly rock con- 

 tained lime enough (it sometimes contains over fifty per cent, of the carbonate) to make 

 it of the slightest value ; but it is now sometimes burnt for agricultural purposes. Nor 

 is it known even now that it is the slow decomposition of this rock which produces those 

 fine crops of grass and other products which one meets at the eastern part of the Green 

 Mountain slope, as we ascend from the Connecticut valley, all the way from Connecticut 

 to Canada. The surface is very much broken and the hills steep, yet they furnish some 

 of the richest soil in New England, though often the naked rock occupies a good deal of 



