Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/344

 in this paper, that it passes into granite, and is associated with it in an intimate manner, having no further the appearance of stratification or of an overlying character than granite has, and bearing precisely the same relation to the stratified rocks which that does. In aspect it has generally a considerable resemblance to granite; often indeed it cannot be distinguished without a careful inspection, while the syenite which lies above the secondary socks rarely has a granitic aspect. This variety frequently contains mica as well as hornblende, and it is indeed not rare to find the former ingredient far exceeding the latter. There appears therefore a sufficient mineralogical distinction between these two rocks to justify us in distinguishing them by two names, without infringing the rule which I have suggested on another occasion, that we were not at liberty to vary our principles of nomenclature, by drawing them sometimes from mineralogical character, and sometimes from geological position. But for this purpose it is necessary that the whole of any mass of rock should be considered together, and that its mineralogical character should be defined by its prevailing, not by its occasional composition. Whatever more experienced geologists may determine on this question, it is indubitably necessary that the conclusion which I have here pointed out should be removed by some expedient, and I shall gladly conform to any better suggestion; but it is too plain that the indiscriminate application of the term syenite to two rocks so essentially different in connections, would tend to produce a most incurable confusion in geological description.

The last remark which I shall make on the apparent discrepancy between my observations and those of the philosophers above mentioned, is also little else than a question of nomenclature. It