390 CRYSTALLINE LIMESTONE IN SCOTLAND. 



So extensive a range of limestone rocks in the direction of the 

 strata of mica slate may be regarded as being thoroughout a nearly 

 contemporaneous deposit. The limestones on Loch Laggan and Loch 

 Eil in Inverness, and at numerous other points- in Aberdeenshire, 

 are referred by Boue to the same era. 



The marbles of Sutherland were formerly worked in the Inchna- 

 damph district, near Loch Awe; but they contain gritty particles 

 which interfere with the polishing. Yellow arid green serpentinous 

 marbles occur with others of a chocolate-brown and light-red colour 

 near Ledbeg, and a white marble runs from the south of the Ledbeg 

 river through Loch Urigill towards Elphin. The Loch Ailsh marble 

 forms two beds, a lower white saccharine marble being separated 

 from the upper by a layer of argillaceous chert. The upper bed is 

 less perfectly metamorphosed. This limestone contains about 5 per 

 cent, of carbonate of magnesia, and over 4 per cent, of silica. 



Second Range of Crystalline Limestone. A second range of 

 limestones, lying chiefly in argillaceous and chloritic mica slate, is 

 considered to be of more recent origin. The points where it is seen are 

 near Blairgowrie, at the foot of Ben Vorlich, on the north side of 

 Loch Earn, Balquhidder, Inveraray, Knapdale, and Lorn ; and the 

 limestones of Balachulish, Cairndow, and Dalmally, as well as those 

 which run from Boharm to Banff, are classed with this series. 



Perhaps the relations between all these points may not have been 

 correctly ascertained ; but there seem excellent reasons for admitting 

 that these calcareous rocks, like those which are more perfectly traced 

 among the newer strata, were produced at a few definite periods, 

 and not mere irregular formations having no relation to each other in 

 respect of time. (See Geikie's Geological Map of Scotland.) 



Garnets in Statuary Limestone. Garnets are among the most 

 characteristic products of metamorphism. As a rule, granules of 

 quartz are scattered through the garnets, though in some granitic 

 veins, as to the east of Portsoy, the quartz is arranged in the garnet 

 crystals in a radiating manner. The colourless water garnet, a double 

 silicate of lime and alumina, is remarkable for being free from iron. 

 It is known from limestone quarries in the wood on Craig Mohr, 

 opposite to Balmoral. The lime and alumina iron garnet known as 

 grossular is a rare form found embedded in limestone in green crystals 

 of the colour and size of peas. The lime iron and alumina garnet, 

 termed cinnamon stone, is common in the limestone at Delnabo, 

 Glengairn. The formation of these and the other minerals found in 

 granular limestone is explained by pointing out that the limestone, in 

 developing the crystalline structure of calcite, has extruded from 

 itself the foreign substances it contained, much in the same way that 

 sea water, when it freezes, separates the brine in small globules. 

 Professor Heddle suggests that the high specific heat of limestone may 

 have to be considered as a source of heat liberated when the rock 

 passes from an amorphous to a crystalline condition, and cites many 

 examples of the association of calcareous beds with argillaceous mica- 

 schist, quartzite, and serpentine, especially in Banff, Aberdeen, and 



