270 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
Of Oligoclase,—true angle 86° 10’,—there were got— 
Anguston, : : 86° 10’ 
Lairg, colourless, ‘: 86. 10 
Rispond, : - 86 14 
Craigiebuckler, . : 86 14 
Dyee, . : . 86 15 
Lairg, cream, . 3 86 15 
Rubislaw, : : 86 15 
Coyle, . : : 86 32 
Of Andesine,—angle according to DEscLoIsEAUx 87° to 88°,—there were 
got— 
Glen Gairn, : : 86° 21’ 
Crathie, ; : 86 24 
Glen Urquhart, : 86 28 
Of Labradorite,—true angle 86° 40’,—there were got— 
Kildrummy, . 86° 28’ to 86° 40’ 
Kinneff (curved), about 86 40 
Balvraid, about ; 86 40 
Scavig, . ‘ ; 86 42 
Portsoy, : 86 42 
Badnagoach, . : 86 45 
Of Anorthite,—true angle 85° 50’,—there was got— 
Lendalfoot, hydrous, . 86° 42’ 
This is not altogether satisfactory ; we have much the same overlapping 
that we had in the gravities: an angle of 86° 15’, or under that, would pretty 
certainly indicate oligoclase ;—of 86° 40’ or over it, would indicate labradorite. 
The low angle with a low gravity, and the high angle with a high gravity, 
would make assurance more than doubly sure :—this is about all that we can 
say; and it takes no account of albite, andesine, and anorthite, as regards 
at least their discrimination from one another. 
Albite usually occurs in free'crystals superimposed upon orthoclase ;—this 
is, however, the chronicling of a habit, not the observation of an inherent 
property. 
Truly we are sadly in want of a rapid and trustworthy test. . 
As to whether the eye, with the simple aid of the lens, can be’ dduiskem 
to the recognition of all of these felspars, as they ordinarily occur in rocks, I 
can only say that,—after having selected from the rocks the specimens to 
be analysed, after having manipulated them by grinding on the lapidary’s wheel 

