Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/401

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391
various parts of Scotland.

cumlocution which it would be desirable to avoid, yet till either a system is firmly established on a wide and fair induction, or a set of terms can be produced independent of all system, such circumlocution is perhaps inevitable.

I have only to add, that since the following remarks did not admit of any useful or methodical arrangement, they are placed with little regard to order, and as the subjects of them occurred. That they are so detached, and often so superficial, must be imputed partly to want of knowledge, partly to want of time, and still more to the uncontrollable elements, to which the best laid projects of the mineralogist as of the husbandman must bend.

Rona.

I should scarcely have introduced any remarks on Rona, were it not for the purpose of mentioning that wolfram, hitherto unnoticed in this spot, is found in the granite veins that traverse the gneiss of which this island is principally formed. I may however remark at the same time, that these veins exhibit that variety of granite called graphic, a rock of much more frequent occurrence than it was once supposed. The graphic granite of Rona is distinguished by the great size of the crystals of felspar which enter into its composition, and consequently by the equal magnitude and distinctness of the quartz which fills their intervals. An accurate survey of Rona is still a desideratum for future mineralogists, as the number, magnitude, and peculiar character of the granite veins might give us hopes of detecting in them some of the rarer minerals known to be inmates of such veins, and observed in similar situations in other parts of the earth. I cannot however dismiss this subject of