86 VOLCANIC ROCKS OF SOUTH MOUNTAIN. [bull. 136. 
SIMTLATl ROCKS IN OTHER KEG-IONS. 
These South Mountain volcanics form a part of a belt of similar 
rocks which have been recently recognized along- the Eastern Coast of 
the United States and Canada. 
Such volcanics have been described in New Brunswick by the Cana- 
dian geologists — Bailey, 1 Matthew, 2 and Ells. 3 
More recently, in the Sudbury district, similar rocks have been ob- 
served by Bell. 4 They have been described in Maine by Shaleiy' and ate 
recognizable in Canada, Maine, and New Hampshire through the 
writings of Hunt, Jackson, and Hitchcock, although they were other- 
wise interpreted by these observers. 
Spherulitic volcanics have recently been definitely recognized by W. 
S. Bayley G at Vinal Haven, Maine, and have been studied in detail by 
Mr. G. O. Smith, of Johns Hopkins University. 
They have been identified in the Boston Basin by Wadsworth 7 and by 
Diller, 8 who has studied them in some detail. The thin sections loaned 
by the latter for comparative study have already been mentioned as 
showing a marked similarity to the South Mountain acid volcanics. 
The continuation of the South Mountain volcanics in Maryland and 
Virginia has been studied by Keith. 9 Similar volcanics have been found 
in North Carolina by Professor Williams, 10 in South Carolina by Lieber, 11 
and in Georgia by Professor Pirsson. 12 
In Canada, Maine, in the neighborhood of Boston, and in Missouri 1 ' 
the felsites were, like the South Mountain rocks, first regarded as sedi- 
mentary in origin, and have only recently been identified as volcanic. 
With continued petrographic investigation of thepre-Cainbrian rocks 
of North America volcanics may yet be recognized at other points where 
the rocks have been interpreted as sedimentary. 
In the Lake Superior region they have long been known through the 
writings of Irving and others, and their extent in that region has 
recently been still further enlarged. 14 
'Bailey, Report on the pre-Silurian rocks of South New Brunswick : Rept. Can. Geol. Survey, 1877-78 
D. D. 
^Bailey, Matthew, and Ells, Report on Southern New Brunswick : Rept. Can. Geol. Survey, 1878-79. 
3 Ells, Volcanic rocks of Northern New Brunswick: Rept. Can. Geol. Survey, 1879-80, D. 
<Ibid., 1889-90, F, 1891. 
'Shaler, Cobscook Bay, Maine: Am. Jour. Sci. (3), Vol. XXXII, 1886, p. 40. Mount Desert: Eighth 
Ann. Rept. U. S. Geol. Survey, 188G-87, pp. 104:3, 1054. 
«Bull. Geol. Soc. Am., vol. 0, 1894, pp. 474-470. 
'Wadsworth : Bull. Mus. Comp. Zool. Harvard Coll., Vol. A r , No. 13, p. 282. 
'Diller, op. cit. 
'Keith, op. cit. 
10 For full statement of distribution of volcanic rocks on Atlantic Coast, see paper by Professor Wil- 
liams in Jour, of Geology, Vol. II, No. 1, pp. 1-31. 
"Lieber, Report on the survey of North Carolina, 1850, 2d ed., 1858, p. 31. 
12 A section of a Georgian felsite, loaned by Professor Pirsson, has already been alluded to. 
13 Haworth: Am. Geologist, Vol. I, 1888, p. 280; Bull. Missouri Geol. Survey, No. 5. 
14 U. S. Grant, Volcanic rocks in the Keewatin of Minnesota: Science, Vol. XXIII, Jan. 12, 1884, 
p. 17. 
