Oil JYorih American Spiders. 99 



ped with this rock, which seems to- resist the action of the weather, 

 better than those with which it is associated. 



Magnetic iron ore is found in the Highlands, in very numerous 

 beds and veins, in gneiss, and sometimes in other rocks. Copper 

 and iron pyrites generally accompany it, in small quantity, as well as 

 augite, hornblende and its varieties, and some other minerals. Four 

 of these ore beds, only, are wrought to much extent. 



Magnetic iron sand covers the shore, three fourths of a mile north 

 of Cold spring landing ; but it may be seen almost any where in the 

 Highlands, after a rain, by examining where the water has washed. 

 In the red limestones of the Highlands, scapolite, hornblende, and 

 phosphate of lime, are usually associated, and in the white ones we 

 find brucite, and spinelle, or graphite, mica, and hornblende ; and 

 where serpentine is in connexion with the limestone, we usually find 

 diallage, amianthus, diopside, and the coccolites, white, red and green. 



With the augite rocks, we find fine glassy feldspar and adularia, 

 with mica, sometimes in six sided prisms, scapolite, crystallized and 

 massive, sphene, and copper and arsenical pyrites in small quantities. 

 Blende and carbonate of zinc are occasionally found, in loose masses, 

 but I have never seen them in place. 



Sulphuret of molybdenum is found in small quantity, and wherever 

 I have seen it in place, in the Highlands, its matrix is a milky quartz, 

 forming beds or partings of small extent between the strata of gneiss. 



Sulphurets of lead and silver, are said to have been found ; but 

 I have never seen them in place. 



I have said nothing concerning the order of superposition, in the 

 rocks in the Highlands, because I am not perfectly satisfied as to 

 their relative position. 



Art. XIII. — On North American Spiders; hy N. M. Hentz, Prin- 

 cipal of the Female Seminary at Covington, Kentucky, and late Pro- 

 fessor of Modern Languages in the University of North Carolina. 



Letter to the Editor. 



Amherst College, August 22, 1831. 



PROFESSOR SIliLIMAIV, 



Sir — Some time since I addressed a request to Nicholas M. Hentz, 

 Esq., then Professor of Modern Languages in the University of North 

 Carolina, and now Principal of the Female Seminary in Covington, 

 Kentucky ; that he would furnish me with a list of the Arane'ides 



