44 Dr. Berger 07/ the Isle of Man. 



turn quite brown before the blowpipe. The texture of the lamellar 

 variety is not so close as that of the other. The specific variety of 

 the latter is 2.777, and that of the first 2.820. 



The magnesian limestone that appears along Castle-town river 

 from Ball-Fhallack towards Athol-bridge, is remarkable for a cir- 

 cumstance that has not as far as I can remember been yet noticed. 

 I mean the occurrence of quartz- nodules, sometimes above the size 

 of a pea and even of a bean. The quartz is quite glassy, and the 

 concretions perfectly distinct, as if they had been water-worn and 

 subsequently imbedded in the limestone itself. This is not however 

 a conclusion I should adopt, as it seems to me that their existence 

 may be better accounted for by way of crystallization. The colour 

 of this magnesian limestone varies from bluish-grey to dirty-yellow ; 

 it makes a very slow effervescence with diluted muriatic acid, con- 

 tains rhomb spar either in lumps or on the seams of stratification, 

 and sometimes sparry iron ore ; the latter before the blowpipe as- 

 sumes the character of a slag, which acts sensibly on the magnet, 

 whereas the bitterspath, though it turns brown, is not attractable. 

 The powder of the sparry iron ore of a brown colour efTervesces 

 briskly with diluted muriatic acid. The specific gravity from three 

 specimens is 2.81. 



At Scarlet point the magnesian limestone has a yellowish-grey 

 colour, and is close in its texture. Patches of compact greyish 

 lime-stone are imbedded in it. 



A dyke occurs in the limestone formation at Scarlet point, upon 

 w^hich I shall say no more for the present, as it is a subject which I 

 intend at some future period to bring before the attention of the 

 Society. 



In the little bay of Purl-Keill-Moirrey, the limestone on account 

 of its low retreating strata, imitates a sort of causeway, ending to- 

 wards the high land of Spanish head. 



