Geology, ^c. of the Connecticut. 17 



times the few presented is a square. Thus an idea is con-, 

 veyed to the observer, at first, that the crystals are rectan- 

 gular parallelopipeds and cubes; although it is well known 

 that felspar never crystallizes in either of these forms. 

 The felspar of these imbedded crystals, when broken, ex- 

 hibits the pearly lustre of the folia very well. The granite 

 containing these crystals is almost uniformly of a coarse tex- 

 ture. 



This porphyrltic granite is carefully to be distinguished 

 from glandulous gneiss, which also occurs abundandy along 

 the Connecticut. Let any one pass from Hinsdale, New- 

 Hampshire toWinchester andhe willsee numerous bowlders, 

 often ten feet diameter, of a rock having the granite constit^ 

 uents and exhibiting no appearance of a schistose structure. 

 In one place at least he will cross the rock in place ; and he 

 will have no doubt that it is the most decided granite. And 

 yet it is elegantly porphyritic. This rock occurs also in 

 Chester where Dr. Emmons has traced a range of it five or 

 six miles. Numerous bowlders of this rock are scattered 

 over the town of Wood bridge near New-Haven ; but I do 

 not know from whence they originated. 



Pseudomorphous Granite, 



I put this adjective to a variety of granite that occurs along 

 the Connecticut, not to show my dexterity at coining new 

 terms, put to make myself understood. I am inclined, how- 

 ever, to think that the rock to which I refer is not exactly de- 

 scribed in the geological books which I have seen, unless 

 it be by Cleaveland, when he says, " some varieties (of gran- 

 ite) are divisible into imperfectly columnar or tabular con- 

 cretions." (Mineralogy, vol. 2, p. 732.) It is a coarse 

 grained granite with light coloured quartz and feldspar, ar- 

 ranged in the usual manner. The peculiarity lies in the mi- 

 ca. This is usually dark coloured, and arranged in plates 

 from one to three inches across. The manner in which 

 these are disposed, may be thus explained, Suppose the 

 quartz and felspar to have been cemented together so as 

 to form a perfect graphic granite. Next suppose the mass 

 to be cut in various directions by a fine saw ; and in the 

 spaces thus made, imagine thin plates of mica, not more 

 than /^ of an inch thick, to be fitted. It is obvious that the 



Vol. VI.— No. 1, 3 



