107 Fredericksburg to Boston. [73] A short distance NW of Bot- land, 4 feet of Laurel lime- stone are exposed. The upper Osgood shale is 2 feet thick. The Osgood limestone is 1 1/2 feet thick. The levels be- tween this locality and the next make the lower Osgood shale about 50 feet thick. This apparent great thickness may be due to a northerly dip in the rocks. [72] In Cave Run, Tetradium animum is found bellow- they bridge, in a greenish clay rock. The massive brown rade at the top of the lower Silurian is 9 1/2 feet thick. The basal Niagara consists of thin fine lime- stone courses, light brown, leaving a total thickness of 2-3 feet. If all layers be made in this the Clinton still has a thick- ess of 17 feet. The top of the lower Silurian is at 1060.