PUBLICATIONS, ~ 223 
Ells* states that the mica and biotite of the Laurentian of Canada 
is confined to a horizon composed of a series of gneisses of the upper 
portion of the Laurentian, siliceous rocks which underlie the limestone 
proper. This horizon graduates upward by regular passage through 
the interstratification of calcareous layers into the massive crystalline 
limestone formation. 
Whittle? describes the main axis of the Green Mountains as a 
series of sharp, compressed folds striking approximately north and 
south and overturned to the west in most localities so that induced 
schistosity and stratification dip eastward. Localities on the western 
border have a steep westerly dip in many instances; in others the 
border series as a whole is nearly in a vertical position. Many areas 
occur along this belt where the series is overturned to the west, but the 
exact angle at which the strata lie is difficult of determination. The 
orographic thrust producing the folding was directed nearly east and 
west. Normal faults and overthrusts are indicated, but data for their 
detection are not now at hand except in one instance. 
Whittle? describes the pre-Cambrian rocks of Vermont as consist- 
ing of two series of Algonkian rocks. The Lower Cambrian quartz- 
ite is apparently underlain conformably by the upper of the two, or 
the Mendon series. That the two are, however, really unconformable 
is supported, among others, by the following reasons: The extreme 
lithological diversity of the metamorphic series as compared with the 
quartzite; a close folding in the Mendon series not observed in the 
quartzite, and by the fact that the quartzite reposes discordantly upon 
granitoid gneiss to the southward. f 
The Mendon series consists in descending order of the following 
members: mica-schist, with a maximum thickness of 1000 feet; mica- 
ceous quartzite, having a maximum thickness of 500 feet and carrying 
several thin beds of crystalline limestone; crystalline limestone, with 
a maximum thickness of 4oo feet; conglomerate schists and quartzite 
with a maximum thickness of 700 feet. At Mendon the section has 
*Mica Deposits in the Laurentian of the Ottawa District, by R. W. ELis. Bull. 
Geol. Soc. Am., Vol. 5, pp. 481-488, 1894. 
? General Structure of the Main Axis of the Green Mountains, by C. L WHITTLE. 
Am. Jour. Sci., Vol. XLVII., No. 281i, pp. 347-354, May, 1894. 
3 The Occurrence of Algonkian Rocks in Vermont and the Evidence for their Sub- 
division, by C. L. WHITTLE. JouR. GEOL., Vol. II., No. 4, pp. 396-429, May-June, 1894. 
