ESSEX COUNTY. 231 



hornblende which may be found upon the west of the boundary Hnc as given. The high 

 range of mountains west of the valley of Schroon river, may be cited as a region where all 

 traces of gneiss and hornblende are lost, and the range terminating in Spht-rock as being 

 wholly free from intermixture of hypersthene. 



The dip of the rock forming the gneiss and hornblende district is generally east, though, as 

 has already appeared, examples arc not wanting of a dip in the opposite direction. The 

 amount varies from fifteen to seventy or eighty degrees. The disturbances in the dip, and 

 in other respects, appear greatest in the iron veins, or else they are there better disclosed by 

 mining. Contortions, inversion of dip, and anticlinal axes, are not uncommon at many of 

 the veins. 



A noted point of rock terminates this range upon the lake : it is Split-rock, a prolongation 

 of the range a little distance into the lake, but joined to the main land by a narrow neck. 

 This neck is composed of a hornblende containing pyrites, in consequence of which it is 

 brown, and often slightly porous ; but what gives origin to the term Split-rock, is the deep 

 wearing away of this neck for the space of about ten feet, which cuts off half an acre of the 

 extreme point of the range from the main land. When the water in the lake is high, this bit 

 of land is apparently entirely separated from the main land by a deep fissure ; but in low 

 water, the connection is still perceived to exist. The common opinion is that this small piece 

 of land was separated by a convulsion of some kind. The fact seems to be, that no other 

 chant^e has taken place, than what has arisen from the decomposition of a mass containing a 

 large amount of pyritous iron. 



Magnetic Oxide of Iron. 



Veins which belong to gneiss and hornblende, and occupy the southeastern part of the 



county. , 



The first vein which I shall describe, is on lots Nos. 45 and 46, Paradox tract, and known 

 as the Penfield ore bed. The ore is black, and gives throughout the whole mass the black 

 streak, showing that it has undergone no very marked change in its state of oxidation. The 

 lustre is bright metallic only where the fracture is fresh, and a new surface is exposed. The 

 mass, as a whole, is dull, which is always considered an indication of a good variety of ore, 

 and one which will reduce easily. The width is about forty feet, and its course northeast and 

 southwest, or nearly in the direction of the line of bearing of the gneiss in which the ore is 

 embraced. The middle part of the vein is a rich mass, and contains but a small proportion 

 of rocky matter ; towards each side, the ore diminishes in quantity, and becomes mixed with 

 quartz, or lean, as it is termed ; there being probably as much of the latter mineral, as of 

 the ore. This pure mass of ore maintains its central position as far as the vein has been 

 explored, a distance of from sixteen to twenty rods. 



This vein is one of those in which the width varies considerably at different points : thus, 

 from a width of forty feet, it swells out to one hundred and sixty ; the ore is lean, however, 



