? 
relative degree of abundance. There is a complete transition from the oldest and most regular 
granite to rocks differing in nothing from recent trap unless in possessing hornblende instead 
520 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
of augite. 
The observations that have to be made upon the above very precise state- 
ments, of two very precise observers, are,—that the interchanges and transitions 
referred to are certainly to be seen in the rocks of the trough which lies between 
Bennachie and the Froster and Barra Hill ridge ;—that our knowledge regarding 
the different felspars now enables us to follow out to a certain extent the pre- 
cise nature of the interchanges ;—-that the connection of the rocks of this trough 
with those of the north and south line of strata to which I have been directing 
attention has not only never been made out,—but that, in that north and south 
system of rocks, any transition into the granites there occurring is absolutely 
denied by CUNNINGHAME, and can at Barry quarry be clearly seen not to exist ;— 
and, lastly, that if such a connection be proved, then so much the worse for the 
granite of the eastern districts of Aberdeen,—so far as regards the maintaining 
that it is of an igneous and not a metamorphic nature. 












15. From the diorite of Glenbucket. 
The mode of occurrence and associates have been already noticed in the 
chapter on Felspars. This hornblende, though occurring in comparatively 
small quantity, surpasses everything of a similar kind in the startling magni- 
tude of its crystals, and the striking contrast which their brilliant blackness 
offers to the snow-white labradorite in which they are imbedded. 
Crystals over 21 inches in length by 2 in breadth have occurred here; 
through the breaking up and removal of the larger masses for rockeries, the 
finest have now been defaced. 
This hornblende bears a very strong resemblance to Arfwedsonite. It 
fuses readily ; its cleavage angle is 124° 24’, and its specific gravity is 3° 218. 
Silica, “ . °638 
From Alumina, . -037 
*675 — 45° 
Alumina, . a : a 9 Al? 
Ferric Oxide, . E fe) Ayoe 
Ferrous Oxide, . ° 9) 16° os 
Manganous Oxide, . ; * 333 
Lime, . P : =, play, 
Magnesia, : ; . Lt 193 
Potash, , : : af, 300 
Soda, iL 663 
Water, ists 

