GEOLOGY OF SARATOGA SPRINGS AND VICINITY I35 



every allowance for that it still seems to us that the very oldest 

 Tertiary is the youngest age that can possibly be ascribed to the 

 rock, all the conditions considered. Since igneous action of such age, 

 or of any Tertiary age, is wholly unknown in the eastern United 

 States, a reference to the Newark seems to us more reasonable. 

 Yet we candidly admit the peculiarity of the rock and its' isolated 

 occurrence, and have no quarrel with anyone who is disposed to 

 take a different view. There is one character of the lava which 

 suggests recency, and that is the unaltered and undevitrified char- 

 acter of the glass. 



To sum up, the only definite statement that can be made concern- 

 ing the knob is that it consists of a small mass of lava of effusive 

 type. If it is in place it seems surely a volcanic neck or throat ; 

 if not in place it may be a fragment of a surface flow, overthrust 

 from some locality to the east. If in place it is younger than 

 the date of the overthrusting ; if not in place it is older. If not 

 in place we have no idea whence it came, nor are any other frag- 

 ments known. It has some features in common with certain New- 

 ark trap flows and is like some of them in composition, though 

 the composition differs from that of the average Newark trap. 

 Clear structural evidence of much shearing and faulting of the 

 knob, of such type as to indicate deformation under load, leads to 

 the conviction that the lava can not be an especially recent one. 



HISTORICAL GEOLOGY 



BY H. P. GUSHING AND R. RUEDEMANN 



Precambric. Our direct knowledge of the events of Precambric 

 time in the region commences with the deposition of the Grenville 

 series. These rocks are very widespread and very thick, with 

 great amounts of shales and limestones and a lesser amount of 

 sandstone. They must have been deposited on some floor of older 

 rocks which has since been entirely destroyed by igneous action, 

 or else yet remains to be discovered. Judging by their extent and 

 thickness the series was probably deposited under marine conditions 

 but, lacking fossils, there can be no certainty in the matter. 



Following the deposit of the Grenville sediments the region was 

 repeatedly invaded from beneath by great masses of igneous rock. 

 The earliest and most widespread of these invasions was that of the 

 Laurentian granite. Subsequently came invasions of anorthosite, 

 syenite, granite and gabbro. These broke up the Grenville rocks 

 into groups of fragments, apparently ate away and digested much 



