Dr. M*t^uLLocH's Additional Remarks on Glen Tilt. 67 



crystals radiating- from a centre : it presents a singular as well as beautiful 

 specimen for collectors. 



4. Transparency, at least to a certain degree^ has I believe been consi- 

 dered a characteristic of tremolite. A variety is however found in this place 

 of a whitish green colour^ and perfectly opaque. As is usual among the more 

 common kinds^ it is radiated ; the radii being about an inch in length. The 

 form of the crystals is however imperfect ; and their disposition more confused 

 than in the ordinary kinds. 



5. Tremolite is found also among the limestone of this district, in other 

 situations besides Gow's bridge, where I originally discovered it. The most 

 remarkable variety which occurred consists of broad laminse^ radiating from a 

 common centre, and of course presenting greater dimensions at the circum- 

 ference than the centre. The length of the radii extends to four or five inches, 

 and their breadth from an eighth to a sixth, or even to a quarter of an inch. 



6. The next variety wliich appears to merit notice consists of spheres, from 

 halt' an inch to an inch in diameter, imbedded in the limestone. They are 

 generally placed at a small distance from each other, and, as they are much 

 harder than the including rock^ are readily discovered in water-worn frag- 

 ments ; often projecting a semidiameter beyond the worn surface. Occa- 

 sionally they present a fibrous and radiated structure ; but they are often 

 extremely compact, and the structure consequently very obscure. They are 

 of a sea-green or pale beryl colour. 



7. The very fine fibrous variety occurs also here of a pale green colour, 

 and in considerable quantity. The fibres are fasciculated and parallel, often 

 exceeding six inches in length, and either straight or curved ; and the lustre 

 resembles that of silk. 



8. Lastly, this mineral is found of a similar green colour, but in the form 

 of crystals, from an eighth to the fifth of an inch in diameter, entangled 

 together so as to constitute a solid mass of considerable hardness when dry ; 

 but, like all these substances, extremely tender when first taken from the 

 quarry. 



I formerly mentioned that tremolite and sahlite were found in the same 

 place, and in contact; but was not then quite aware of the intimacy of their 

 connexion. They are occasionally so intermixed together, that it is not 

 easy to be certain that the one mineral does not graduate into the other : 

 and it is not impossible that such a transition does actually take place. It is 

 also a remarkable fact, that wherever I have observed sahlite in Scotland, 

 there tremolite is likewise found, and always in the same intimate union. 



k2 



