264 . PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
recurring question as to the specific distinction between the meals —the 
number of species into which they are to be divided. 
In speaking of the light that may be thrown upon the question, I would not 
have it thought that I consider it now as an open one; I conceive that the 
masterly paper by DEscLoIsEAux in the Comptes rendus* has definitively settled 
the matter, and must have satisfied TscHeERMAK himself. Nor would I reduce 
it to a mere question of personal opinion or experience, by enumerating the 
grounds which have induced me long to take the view advocated by Dzs- 
CLOISEAUX ; but,—postponing, to the second part of this paper, the chemical , 
consideration of the subject,—I would only endeavour meantime to strengthen 
his position by drawing attention to the evidence of the rocks themselves, as 
clearly declared by the stratigraphical position of the minerals.. 
All mineralogists admit the three species, orthoclase, albite, anorthite ; — 
some also labradorite,—but do not admit oligoclase or andesine. 
It appears to me that, in Scotland, the lithological relations of the three last 
bear out their specific individuality quite as thoroughly as that of the univer- 
sally acknowledged species is borne out. 
Reviewing each in turn,—and admitting only the evidence of such speci- 
mens as have either been actually analysed, or otherwise determined by 
characteristics sufficiently cumulative to leave no room for doubt,—we find true 
or ordinary orthoclase occurring in crystalline schists—as in gneiss at Glen 
Urquhart, Dee side, and central Sutherland; the associated minerals being 
hyaline quartz paste, carrying either Haughtonite or lipidomelane, and rarely 
apatite. Rarely in cavities of chlorite schist, as in Strath Alnack; the associates 
being chlorite and rutile. Exceptionally, otherwise than crypto-crystalline, in 
porphyry, with granular quartz and pinite, or black hexagonal mica (? Biotite) 
as associates. Exceptionally in syenite, as on Morven and Froster hills, and 
near New Leslie, in Aberdeenshire; the associates there being hornblende, | 
menaccanite, and sphene. And very exceptionally (necronite) in granular 
limestone, the immediate associates being Biotite, balvraidite, and hydrous 
labradorite. 
The more sodaic sanidineés occur in tufa or in pitchstone. 
The corded orthoclases alone occur in granitic veins or bands; the ordi- — 
nary associates being oligoclase and Haughtonite in a quartz paste ; the more 
occasional associates, arranged in the order of the frequency of their occurrence, 
being either muscovite or lepidomelane, tourmaline, apatite, garnet, beryl, 
magnetite, rarely ilmenite and pinite ; and—where the veins cut syenite,— 
sphene, menaccanite, Allanite, Babbingtonite, zircon, and thorite. 
Though a constituent of a greater number of rocks than any other of the 
* 8 Fevrier 1875. 


