REPORT OF THE DIRECTOR I913 61 



northeast-southwest strike of this channel is accounted for. 

 Nothing very positive can be said regarding the amount of dis- 

 placement and date of this fracture but its presence is demon- 

 strated by fine crushed and broken rock zones at Buttermilk falls 

 and several places in the ledges along the shores of the lake. 



Glaciation. A number of good glacial striae were observed 

 especially near Long Lake village and toward the western base of 

 Blue mountain. These bear from south 30° to 50° west, thus 

 harmonizing with other observations in the interior Adirondack 

 region. Much glacial drift has been deposited, particularly over 

 the lowlands, but there is no good evidence for ice erosion other 

 than the removal of superficial loose or decomposed materials. 



Brier Hill and Ogdensburg quadrangles. Professor Gushing 

 was engaged for part of the summer of 1913 in the Brier Hill and 

 Ogdensburg quadrangles and reports that, so far as his observa- 

 tions have extended, the Precambric rocks are of considerable 

 interest. There are long, narrow tongues of porphyritic syenite 

 cutting the Grenville rocks and in parallelism with their structure. 

 It is suggested that they are of the nature of huge dikes, but if 

 this is the case the parent body of syenite from which they sprung 

 nowhere appears and must lie to the south on the Gouverneur 

 sheet. There is much amphibolite and interbedded Grenville sedi- 

 ments cut by the porphyritic syenite. Part of this amphibolite, 

 however, into which the porphyritic syenite appears to grade, is 

 evidently igneous, yet so far it has proved impossible to distinguish 

 certainly the two in the field. 



The Paleozoic section is well shown on these two quadrangles 

 and is of much interest. The Potsdam sandstone is thin and of 

 unequal thickness owing to the irregularity of the surface on which 

 it was deposited. It is quite like the Potsdam of the Alexandria 

 Bay and Theresa region described in Museum Bulletin 145. The 

 overlying Theresa formation has greatly thickened and in its upper 

 portion carries a massive 20 foot sandstone which is prominent all 

 across this district and, according to Professor Chadwick, is con- 

 tinuous into the Canton quadrangle. The horizon is fossiliferous 

 but until a definite examination of the fossils has been made it 

 is not practicable to say whether this sandstone and the overlying 

 beds are positively of Theresa or whether they may be of the age 

 of the Tribes Hill formation. The overlying Beekmantown for- 

 mation has a thickness of about 100 feet, with no summit shown. 

 It is highly fossiliferous and these fossils indicate that the base 



