Miscellanies. 375 



tallized in rhomboidal tables or plates, sometimes ten ov twelve inches 

 by four; the laminae or planes can be separated very easily. The 

 crystals assume a great variety of forms and are very well defined ; 

 fifty plates may be split with a knife from a crystal half an inch thick, 

 and these may be cut with a scissors and shaped to fit the frame of 

 any spectacles, and of any thickness, to suit the sight or the object of 

 the wearer ; for instance, if to screen the eyes from the intense light 

 produced by the galvanic deflagrator, the plates must be thicker than 

 when used in the day time to shade the eyes from the usual light of 

 the sun or the snow. 



Remark. — The mica transmitted by Dr. Meade produces a most 

 agreeable effect; the light transmitted to my eyes is yellowish green. 

 — Editor. 



13. Geological Facts, by David Thomas: communicated through 



Prof. Eaton. 



The rocky strata of this region have a general dip to the south. 



The new channel of the Seneca River near Jack's Reef, made 

 for the purpose of draining the Cayuga marshes, is nearly in a north 

 or south direction. The rock excavated is a soft or slaty limestone, 

 repeatedly alternating with marl ; and nothing can be more obvious, 

 in the sides of this cut, than the dip of these strata to the south. 



In a cove on the east shore of the Cayuga Lake, five miles to the 

 south of East Cayuga village, a valuable quarry of water lime has 

 been wrought for building stone ; but at Cook's quarries, two miles 

 above, and at Long Point, we find the geodiferous limerock. The 

 latter in all cases overlie the former ; and as these quarries occur at 

 the surface of the lake, the dip of the strata to the south is evident. 



A mile further up, the pyritiferous slate, which overlies the geo- 

 diferous limestone, first appears on the shore, and also demonstrates 

 the dip to the south. From this point upwards, the slate abounds 

 on both shores, to the head of the lake ; but the prospect of some 

 inclined strata, from the ferry-boat near Kidder's, is very interesting. 



In going up the canal from Lockport, the dip of the strata is very 

 apparent ; and though the course of the canal varies, in about two 

 miles the whole mass of rock disappears. It is true, some rocks oc- 

 curred further south, but these were super-imposed strata, and in a 

 short distance in that direction, sunk below the canal. 



