No. 7.] HUNT — GEOLOGY OF PORT HENRY, N. Y. 421 



in the fissures of the broken gneissic strata, and are not unfre- 

 queotly brecciated, as in the present case. These calcareous 

 masses are not eruptive but endogenous. The Laurentian 

 rocks abound in similar instances. (^Second Geol. Survey of 

 Penn., Keport E, pp. 166, 167.) 



A few miles north from Port Henry the gneiss, with its mag- 

 netites, i.s replaced by the massive bedded labradoritic rocks of 

 the Norian series (the hypersthene rocks of Emmons) with great 

 masses of titanic iron-ore, which latter abound near Westport. 

 Prof. Hall has described these rocks as newer and unconformable 

 with the underlying gneiss ; which accords with the numerous 

 observations of the relations of these two series made in Canada. 

 The Norian I'ocks are well displayed along the railway between 

 Westport and Port Kent, where a nearly continuous cutting of 

 about five miles through them, around Wiillsborough Bay, afi"ords 

 a good opportunity for their study. Prof. Leeds has lately pub- 

 lished a valuable series of chemical and microscopical studies of 

 the Norian rocks of this region. ' 



The Potsdam sandstone, the basal member of the overlying 

 paleozoic series is well seen in a railway-cutting at Port Henry. 

 The lower beds are massive and compact, dark bluish or iron-gray, 

 with lighter bauds and thin blackish shaly layers. Dipping 

 gently to the northwaid, they become overlaid by the higher beds 

 of the division, which are light gray and porous, <and composed 

 apparently of agglutinated silicious grains, as if deposited from 

 solution, as long ago remarked by Prof. Hall for the similar 

 strata of Iowa. Some of those upper layers have irregular cavi- 

 ties, as if from the disappearance of organic remains, and others 

 exhibit numerous vertical cylindrical markings difi'ering alike 

 from the ScoUthus linearis of the Primal sand>tone and the >S'. 

 Canadensis of the Potsdam of the Ottawa basin. The mark- 

 ings at Port Henry are small vertical cylindrical cavities, often 

 ei<j;ht or ten centimetres in leuoth and about three millimetres in 

 diameter; having a concentric interior tube or cylinder of about 

 two millimetres external and one millimetre internal diameter, and 

 sometimes exhibiting traces of concentric layers. Farther study is 

 needed to determine the origin of these markings which I have 

 elsewhere described. (^Second Geol. Survey of Fenn., Report E, 

 p. 138.) 



Above these sandstones are seen massive layers of an impure 

 dark bluish limestone without observed fossils, holding eighteen 



