314. This result may perhaps fall as much short of Mr Kirwan's notion, as it exceeds the estimate made by Dr Hutton. If it shall not, and if the former has, in this instance, come nearest the truth, it cannot be ascribed to the accuracy of his information, or the soundness of the principles which directed his research. Mr WILLIAMS, whom he quotes, was a miner, of great skill and experience in some branches of his profession, to which, if he had confined himself, he might have written a book full of useful information. What he says on the subject of granite, is, in the main I believe just; but it is far too general to authorize the conclusion which Mr Kirwan derives from it. Dr Ash, for whose judgment I have great respect, cannot, I think, have meant, when he used the expression granitic rocks, to describe granite strictly so called. He says, in the passage quoted by Mr Kirwan, that "from Galloway, Dumfries, and Berwick, there is a chain of mountains, commonly schistose, but often also granitic." Now, the fact is, that the great belt of primary rock, here alluded to, which traverses the south of Scotland, consists of vertical schistus of various kinds; but except in Galloway, and again in Lammermuir, near Priestlaw, it appears, as already mentioned, to contain no granite whatsoever. If the German mineralogist quoted by Mr Kirwan, when he says that the Grampian mountains consist of micaceous limestone, gneiss, porphyry, argillite, and granite, alternating with one another, means only to affirm that all these stones are found in the Grampians, he is certainly in the right, and the catalogue might easily be enlarged; but, if he either means to say, that these are nearly in equal abundance, or that the granite is commonly found in strata alternating with other strata, I must say, that these are propositions quite contrary to any thing I have ever seen or heard of those mountains. But it is probable that this is not meant, and that the fault lies in understanding the expressions much too literally. Mr Kirwan accuses Dr Hutton of not knowing where to look for the granite; not aware of how much, notwithstanding any error committed in the present estimate, he was skilled in the art of mineralogical observation; an art, which those who have not practised do not always know how to appreciate. But, however imperfect Mr Kirwan's knowledge of this subject has been, he has here had the good fortune to correct a mineralogist of very superior information. The mere disposition to oppose is not always without its use: no man is in every thing free from error, and, to controvert indiscriminately all the opinions of any individual, is an infallible secret for being sometimes in the right. NOTE XVI. § 100. _Rivers and Lakes._