86 O F S T ON E S. 



ly. Of a flat fhape on one fide, and roundifh on tfce other, of 

 abluifh-grey. From the fhore of North Tyne, near Park-End. 

 Thefe are opake. 



^thly. Of an oblong, flat fhape, of a pearl colour, with white 

 reticular veins, like thofe we fee in the leaves of fome vegetables, 

 From the fhore of the brook near Nun-wick. 



. Of an ovated fhape, and of the fame colour. From 

 fliore of the Tweed. On receiving a beam of light, it refracts it 

 mofl beautifully, like the IJland-cYyft.d\ of authors. 



They are all of a fmooth furface, and capable of a neat 

 polifh. They are commonly taken by inaccurate obfervers for 

 fparry nodules, 



Of Pebble-CryJlal (c) we have fome very fine, on the fhores of 

 the Coquet and Tweed ; from the fize of a pea, to that of a large 

 walnut, and fometimes larger, of an unequal and irregular fur- 

 face, ufually roundifli or flattifh, pellucid as water, and capable 

 of a high polifh. I have one, from the fliore of the Tweed, three 

 inches long, two inches and a half in diameter, and about an 

 inch and a half thick, I have others, from the fame fhore, of 

 all the intermediate fizes between that and a large garden-pea. 

 It is never found with figured concretions. 



Of thefarda, or carnelian, we have the fed (d), the yellow (ej, 

 and the white (f), on the fame fliore. We have the red from half 



(c) Petridium chryftallinum, pellucidum, decolor varium. Hill. Hift* FolT. p. 563. 

 No. i. 



(d) Sarda rubefcens, Id. p. 458. No. 1. 



(e) Sarda flavefcens. Id. p. 460. No. 2. 



(f) Sarda albefcens. Id. p. 461. No. 3. 



an 



