VARIETIES OF ATLANTIC SEABOARD GRANITES 377 



fulfill this requirement, the general run of the stone contains more 

 oligoclase. 



General Remarks on the Granites of the Atlantic Seaboard 

 statistics of varieties 



All persons familiar with either the rocks or the quarry industry of the 

 Atlantic states are aware that granites are exceedingly abundant through- 

 out the region. In the maritime provinces of Canada they are likewise 

 present in vast amount. In southern Nova Scotia the slates and schists 

 of supposed Algonkian age are penetrated by them, and exhibit zones 

 of contact metamorphistn.''^ In New Brunswick, both along the imme- 

 diate coast and in the interior, granites are known to exist in abundance, 

 and in some instances to be as late as the Devonian. f Throughout New 

 England and the crystalline areas of the states to the south, granites are 

 among the most common rocks. | While they have suffered much from 

 dynamic metamorphism in one place and another, yet there are many 

 that are still massive and that are typical eruptives. They are so often 

 situated near tidewater, or else they possess such other advantages for 

 economical transportation, that they have been very extensively utilized 

 for building stone. As a result, they have been widely distributed, and 

 in most cases have been already determined with the microscope and 

 recorded in the reports on building stone which have been especiall}' pre- 

 pared by G. P. Merrill.§ The writer has also had his attention directed 

 to the same subject in connection with lectures to students in courses on 

 architecture, and has had the opportunity to study the Tenth Census 

 collection of cubes which is exhibited in the American Museum of 

 Natural History, New York. Considerable experience has likewise been 

 gained in the field. 



The preponderance of biotite granites in this portion of North America 

 is very striking, as will be seen from the following tabulation, which is 



* J. E. Woodman : Studies in the gold-bearing slates of Nova Scotia. Proceedings of the Boston 

 Society of Natural History, vol. xxviii, pp. 375-407; especially 392. Mr Woodman gives a valuable 

 bibliography. 



t Bailey and Matthew, in Annual Report of the Geological Survey of Canada for 1871, p. 180. 



J An excellent review of these, with a bibliography, will be found in the jjaper by George H. 

 Williams on " The general relations of the granitic rocks in the middle Atlantic Piedmont plateau." 

 It is far from the writer's purpose in the present paper to repeat any of the points set forth in the 

 admirable survey of these eruptives that is presented by Doctor Williams, whose intention in 

 writing his paper was clearly to demonstrate their abundance, to record what was known of their 

 eruptive character, and upon this to base an argument for the eruptive nature of many of the 

 gneisses in the great crystalline complex. The particular petrographic characters of the granites 

 outside of Maryland receive but passing mention, and it is the purpose here to emphasize their 

 remarkable uniformity. 



gG. P. Merrill, in Tenth Census Reports, vol. x, pp. 52-77. 



LIV— Bull. Geol. Soc. Am., Vol. 10, 1898 



