66 Ailing — Problems of Adirondack Precambrian. 



This unusual laccolithic diabase is exceptionally well 

 shown by the excavation made for the state road that 

 runs from Chestertown to Hague. 



Kemp and Marsters 38 have emphasized the variations 

 in the diabase dikes, especially those occurring in the 



Fig. 3. 



*-AK£ 



L Af N 



Sf>Ut T\ocK 

 Point 



D\VvE" 



10 



l : i:-l BostoTute 



Camy>toirute 

 Diabase 



Fig. 3. Sketch map and detail drawing of "Three story dike" on 

 Split Eock point, Lake Champlain, N. Y., H. L. Ailing, 1918. 



Champlain Valley. Just north of the lighthouse on Split 

 Eock, Willsboro sheet, a group of dikes of unusual 

 interest is located. "When Kemp and Marsters visited 

 this locality a boathouse, situated astride them, obscured 

 them from view. This building has subsequently been 

 removed, giving access to them. Apparently a dike of 

 nearly normal diabase, originally 6 or 7 feet wide, per- 

 haps slightly porphyritic and approaching an augite 



88 Kemp, J. F., and Marsters, V. F. : TJ. S. Geol. Surv., Bull. 107, 1893. 



