GEOLOGY AND MINERALOGY. 493 



the tliovas:, if a constant character, seems mucli more important, and furnishes a 

 more marked feature for the separation from Olenus. 



Geological position. — In the shales of the Hudson Eiver groujj. 



LOCAL GEOLOGICAL NOTES ; BY E, J. CHAPMAN. 



Preserice of Colmnnaria alveolata and Sfromatocerium rugosum in Trenton 

 Limestone. — Until a comparatively recent period these fossils were considered 

 eminently characteristic of the Black River Limestone. They were not known, 

 indeed, to pass upwards out of that division ; a condition which perhaps still 

 obtains in the geology of New York. In parts of Lower Canada, however. Sir 

 "William Logan, and the other officers of the Survey, have discovered these forms 

 in direct nssociation with fossils of the Trenton Limestone, properly so called • and 

 in the shale of Tennessee, Prof. Stafford, of the Cumberland University, has found 

 them occupying a high position amongst the Trenton beds. J3ut, so far as reo-ards 

 Western Canada, I am not aware that these types have hitherto been recocuised 

 above the Black River subdivision of the great Trenton group. It may not be 

 therefore, witliout interest to state, that I have lately found Golumnaria alveolata 

 in the vicinity of Belleville, C. W., and examples of both Columnaria alveolata 

 and Stromatocerium rugosum at Shannonville on the Shannon or Salmon River 

 about eight miles east of Belleville : these fossils, at each locality, accompanyino- 

 well-known Trenton types. Some additional remarks on this subject will be given 

 in a review of the geology of Belleville and its vicinity, to appear in an early Wo. 

 of the Journal. 



Silicate of Iron in the Limestone Beds of LaTce St. John, Rama, C. IF". At 



the northern extremity of Lake St. John — a small lake lying a short distance east 

 of Lake Couchiching in Rama Township, C. W., — the junction of the Laurentian 

 and the Lower Silurian strata maybe seen ; the gneiss rocks of the former dippino- 

 at an angle of about 25° to the IST. E., whilst the Silurian strata dip at a very 

 slight angle in an opposite direction. A bed of light greenish-brown sandstone 

 about two feet thick, appears at tlie base of the Silurian strata, and siliceous lime- 

 stones, with a few Black River (and perhaps Chazy?) fossils, lie conformably on 

 this. In the bottom beds, more especially, of these siliceous limestones, a number 

 of curious bright- green streaks and markings occur. These at first sight appear 

 to indicate the presence of copper pyrites or other copper ores in the rocks in 

 question. I find them to consist, however, of hydrated silicate of iron; arisino- 

 from the decomposition of iron pyrites; the green substance at least, in some- 

 places, is collected around a minute cube or other nucleus of pyrites, altered into- 

 the brown or hydrated sesqui-oxide. In no case have I been able to detect in these 

 markings the slightest trace of copper. The presence, on the other hand, of silica, 

 oxide of iron, and a little water, is easily made out. 



MINERALOGICAL NOTICES. 



[Condensed, with additional remarks, from various papers in recent Numbers 

 of Poggendorff 's Annalen.] 



Isomorphism of Silica, Zirconia, and Stannic Acid. — G. Rose, from the isomor- 

 phous relations (as discovered by Marignac) of the Fluo-stannates and Fluo-sili- 

 cates, considers the isomorphism of silica and stannic acid an established fact ; and. 



VOL. IV. H 



