fO Mr Haidinger 07i Mesole. 



cies. Sir Charles Giesecke likewise favoured me with some of 

 them, and with the exact indication of their locality, when I 

 had the pleasure of seeing him in Dublin in December last. 

 On comparing these varieties with those of Mr Allan's cabinet, 

 I was struck with the similarity of the surface of the reniform 

 masses with those of mesole, and a more accurate examination 

 of their other properties finally proved them to be the same 

 species. 



Since this is not so much the establishment of a new spe- 

 cies, as an enlargement by several new varieties hitherto not 

 noticed of one already existing, I shall dispense with giving a 

 general description, but in its place shortly enumerate the 

 specimens forming the suite of mesole in the cabinet of Mr 

 Allan, which, I trust, will not be found uninteresting for the 

 comparative novelty of the species altogether, and particularly 

 so in regard to its natural-historical properties. At the same 

 time this case may serve as an instance of the correct applica- 

 tion of the method of mediate determination, as explained by 

 Professor Mohs. * The differences occurring here are only 

 in the size of the individuals ; but this difference is very im- 

 portant, and has often led to the establishment of erroneous 

 species, particularly among the older mineralogists. 



1. A reniform mass on basalt. Colour greyish-white ; com- 

 position distinctly diverging from the centres of the single glo- 

 bular groups which yield a radiated fracture. This is the va- 

 riety analyzed by Berzelius. Mr Allan brought it from Nal- 

 soe, one of the Faroe islands. It occurs near the western 

 shore of that island in soft amygdaloid, disposed on the roof 

 of a large cavern, which has an opening of about two hundred 

 feet in length, but is nearly closed up in front with debris, 

 which gradually slope into it, so that in many places the ca- 

 vern is quite low. It is associated with stilbite, chabasie, and 

 also, though more sparingly, with apophyllite. f In a speci- 

 men of this variety of mesole, which Mr Allan had sent to Mr 

 Mohs, I found the specific gravity = 2.370. 



2. Single globular masses, of a pale greyish-white, disposed 



• Traml, vol. i. p. 388. 



t Trans. Roy. Soc. Edin, vol. vii. p. 233. 



