

SKY. MINERALS. 403 



ment to the collector of specimens. But in general 

 the mineralogist can have no access to any specimens 

 but those which fall from the cliffs and have long been 

 exposed to the violence of the sea and the injuries of 

 the air. However splendid therefore they may once 

 have been, they are not always to be found in a state 

 of good preservation. It is moreover often difficult to 

 gain access to them on any terms, particularly along 

 the other points of this wild shore ; since it is so beset 

 with rocks on which a dangerous surf is almost always 

 breaking, that it requires neither common good weather, 

 nor common dexterity in the management of a boat, to 

 effect a landing and retreat without hazard. 



Analcime is the most common of all these minerals on 

 the shore to which I have now alluded, and is found in 

 the greatest profusion at Talisker. It sometimes occupies 

 cavities of considerable size, in different varieties of the 

 trap, but seems to be far most abundant in the earthy 

 kinds formerly mentioned for which there is no name in our 

 catalogue of terms. Occasionally it forms flat druses of 

 considerable extent, occupying the sides of fissures, while 

 in other cases, a single crystal is sometimes found in a 

 cavity just sufficient to contain it. In the greater number 

 of instances the remaining part of such cavities is filled 

 with the filamentous nadelstein hereafter to be described ; 

 and the crystals seem thus to be imbedded in a mass of 

 cotton. 



The size of the crystals varies from that of a pin's head 

 to the diameter of half an inch; but in general they 

 present only one modification, the twenty-four sided 

 crystal with trapezoidal faces, of greater or less regularity. 

 The only other form which I found was the primitive, 

 and of that I procured but two specimens, while the 

 trapezoidal variety is abundant. The crystals described 

 are sometimes opaque and white, at others they are mottled 

 with a mixture of opaque and transparent parts, while 

 in a third, but less common case, they are transparent. 



