Much difficulty will always exist in determining the age of granite, since no petrographical distinction, sufficiently decisive to warrant us dividing it into classes, exists. The opinion of some geologists that the ordinary syenite, or, indeed, any other variety of syenite hitherto discovered in Southern India, is more modern than the usual ternary granite of felspar, quartz, and mica, is unsupported by any of the usual proofs required by geologists to establish a fact of this nature; viz., superposition; included fragments of rocks of a determined age; intrusion into other rocks, with or without alteration.