1874] 



69 



[Lesley. 



clinal ridge facing Tussey IMountaiu ; Spruce Creek, above the Furnace, 

 flowing between the ridge and the mountain. 



See local map, fig. 37, in lieu of further description ; and the landscape 

 sketches of the excavations, to illustrate their extent and character : fig- 

 ures 39, 40, 41, 42, 43. 



The geologist can here study the theory of the formation of the Lower 

 Silurian Brown-Hematite ores of Pennsylvania to great advantage. I 

 know no better place, and few so good. 



The ores are evidently not washings from a distance ; neither from Tus- 

 sey Mountain, nor from the present surface of the anticlinal ridge ; nor 

 from any formerly existing surface in past geological ages, when the sur- 

 face stood at a much higher elevation above sea level. They are evi- 

 dently and visibly interstratified with the soft clay and solid limestone 



Fig. 36. 



TUB. HOi>Tk.eR ORE. SANK 



layers, and obey the strike and dip of the country ; the strike being along 

 the valley, and the dip about 40° towards the southeast. 



Thousands of minor irregularities prevail ; the streaks of ore and 

 masses of clay, are wrinkled and bunched, and thin out and thicken 

 again in various directions. But all this irregularity is owing to the 

 chemical changes of the strata, and to the changes in bulk of the differ- 

 ent layers during the protracted process of solution and dissolution, during 

 which the looser calciferous and ferriferous sandstone layers have lost their 

 lime constituent, packed their sand and clay more solidly, and perhydrated 

 their iron. In this long process cleavage-planes have been widened into 

 crevices ; caverns have been excavated ; pools or vats have been created ; 

 precipitates of massive (rock and pipe) ore have been thrown down ; and 

 a general creeping and wrinkling of the country been effected. But the 

 original general arrangement or stratification has been preserved ; and 

 those portions of the whole formation, which had but little lime, have 



