430 On the ROCKS in the 



ftained with ferruginous matter. This fact feems connected 

 with the lingular appearances, which occur in the vein of green- 

 Hone, at the level of the junction of the fandftone ftrata with 

 the incumbent bed. 



Without offering any remarks on a fact as yet fo infulated, 

 I content myfelf with merely mentioning it, in hopes that fimi- 

 lar appearances may prefent themfelves to geologifts in other 

 quarters, and perhaps throw fome light on a phenomenon, 

 which by farther elucidation may prove interefting. 



Before I clofe this paper, I mall take the opportunity of pre- 

 fenting to the Society, two fpecimens which were given to 

 me by Sir George Mackenzie, and which I efteem of con- 

 siderable value ; one of them, a fragment of the rock of Salif- 

 bury Craig ; the other, of the Calton Hill, marked in the 

 handwriting of the late Dr'KENNEDY, as the fubftances he ana- 

 lyfed, and of which an account was given in the 5th volume 

 of thefe c T?-ansaclio?is. The great variety in the rock, both 

 of Salifbury Craig and Calton Hill, makes it of importance to 

 afcertain with precifion the kind employed in the refearch of 

 that celebrated chemift ; and as the moft proper place for their 

 reception, I depoiite them in the cabinet of this Society, along 

 with my own collection, under the Nos. 77, and 78. 



igtb 



