PETROGRAPHIC GEPLOGY AND DESCRIPTIONS. 245 



Conglomerate. Breccia. Stilbite, 

 calcite, laumontite. Diabase.] 



No. 183. CONGLOMERATE (ivitli zeolites). 



"A highly pseudamygdaloidal rock, exposed below No. 182, but ascending, at other places when exposed, 

 so as to 'pinch' out No. 182, and almost uniting with No. 181. This crumbles and gets brick-red on weathering 

 on the beach." 



Ref. Annual Report, ix, page 48. 



Mt-y. A soft, earthy, much decayed, brown conglomerate, containing much 

 saponite. Some of the pebbles come out and on being broken are seen to be them- 

 selves highly vesicular. 



No section. 



At/i'. Potsdam. u. s . G . 



No. 184. BRECCIA. 



A vein of this about eighteen or twenty inches wide crosses the face of a crumbling, greenish trap. It 

 runs N. 40 E. One-eighth' of a mile -east of Poplar river. 

 Ref. Annual Report, ix, page 48. 



The hand specimen is a rough mass of breccia. The rock fragments are 

 angular and appear to have been similar to No. 180 or 181, but have been largely 

 replaced by the same minerals which form the cement. The cement is composed of 



ftiiiHHiiitife, a soft gray mineral (tlmlHc ? ) and cult-He. 

 No section. 



Acje. Manitou. u. s. G. 



No. 185. STILBITE, CALCITE, LAUMONTITE. 



Three miles east of the mouth of Poplar river. Zeolite nests which occur in the rock No. 183, or approx- 

 imately the same. 



Ref. Annual Report, ix, page 49. 



The material at hand consists almost wholly of stilbite in large cleavage plates, 

 so twinned as to form more or less radiated and fan-shaped surfaces, with a few pieces 

 of calcite. The stilbite, when separated parallel to its cleavages, and mounted in 

 small fragments in Canada balsam, affords the image of the optic normal in con- 

 vergent light. 



Aye. Manitou. N. H. w. 



No. 186. DIABASE (weatliered). 



" A little further east [about three miles east of Poplar river], can be seen a very interesting instance of the 

 manner of weathering of the trap beds. This is similar to what has been mentioned before, and styled globulif- 

 erous. The rock seems to decay to a considerable depth, and to assume a globular structure, the little globules 

 being rough exteriorly, and generally about one-half inch across. This cannot be due wholly to any peculiarity 

 of circumstance in exposure, sinee here we have an opportunity to see alternations of rough and globular weath- 

 ering and of smooth weathering alternating in beds one above the other, the beds being otherwise outwardly 

 undistinguishable. The rough and globular layers show these characters both near the water and also as they 

 rise obliquely across the bluff, and the same is true of the smooth weathering layers. Samples show both." 



Ref. Annual Report, ix, page 49. 



Metj. There are two hand samples. One evidently represents the globular 

 weathering part; it is a fine-grained, diabasic rock, very similar to Nos. 180 and 181, 

 and it contains large amounts of yellowish thalite. Scattered through the rock are 



