47 



Encrinal limestone. Specimens of Spirifer granulosus (Con- 

 rad) are also common. They are derived from the Demissa 

 bed, which also furnishes the specimens of Stropheodonta 

 demissa (Conrad), though these are of less frequent occur- 

 rence. 



The Encrinal limestone is the most prominent stratum in 

 the bank. It appears for the first time a few hundred feet 

 south of the northern end of the cliff, and gradualh^ descends, 

 until near the middle of the section, at Pike Creek, it passes 

 below the level of the lake. It has the same thickness and 

 character as in the Eighteen Alile Creek sections, and also 

 has the coating of iron sulphide on the under side, which is 

 characteristic ol all its outcrops. Professor Hall states 

 that this coating w^as formerly "wrought to some extent on 

 the supposition that it was silver."* 



From the constant wearing away of the soft Hamilton 

 shales, the Encrinal limestone becomes undermined, so that 

 large blocks break off annually and fall to the beach, where 

 thev accumulate in considerable numbers. Not infrequently, 

 these blocks of limestone are full of fossils, chiefly corals, 

 some of which stand out in relief through differential solu- 

 tion. Thev tempt the collector with visions of choice 

 specimens for the cabinet, but he is apt to be disappointed in 

 his attempt to obtain them, unless he has a good hammer, a 

 number of well-tempered chisels, and plenty of time and 

 patience. A sledge hammer is the most desirable tool in 

 such cases. Unless the collector is properly equipped, he had 

 better not attempt the working of this refractory rock, for 

 he is sure to end in spoiling his tools, his temper, and worse 

 than all, the specimens, which he should leave for some one 

 better prepared. 



The Moscow shales have much the same character which 

 the}' exhibit in the Eighteen Mile Creek sections. Their 

 thickness hardh^ diminishes, and they usualh' contain a fair 

 proportion of concretions. The coral layer appears in the 



*Geol. Rep't, 4th Dist. N. Y., 1843, p. 472. 



