One most important fact should never be forgotten; mineral character, whether of sedimentary or volcanic rocks, is absolutely worthless as a guide to the age of beds occurring in distant countries. The traveller should never be led to suppose, because a formation, whether sedimentary or volcanic, in a remote part of the world, is mineralogically and structurally identical with another in Europe, or some country of which the geology is well known, that the two are of contemporaneous origin. The blunders that have been made from want of knowledge of this important caution are innumerable. There are a few points of geological interest well worthy of the investigation of those who traverse unexplored, or partially explored, tracts of the earth’s surface. Amongst these are the following:— _Mountain-Chains._—Few, if any, geologists now believe that mountains were simply thrust up from below; all admit that, at least in the majority of cases, where great crumpling of the strata has taken place, there has been lateral movement of the earth’s crust. But the causes, extent and date, of the lateral movements are still, to a great degree, matters of conjecture, and every additional series of observations bearing on the question is of importance. There are many mountain-chains of which very little is yet known. In every case good sections are required, drawn as nearly to scale as practicable, through the range from side to side, and including the rocks at each base. The nature and distribution of all volcanic and crystalline rocks, both in the range and throughout the neighbouring areas, are especially noteworthy, and also the relations of the later beds, if any, on the flanks of the mountains, to those constituting the range itself. The derivation of the materials of the former from the latter, and the relative amount of disturbance shown by the two, and by the different members of each, will afford a clue to the date of upheaval; and two or more periods of movement may thus be determined, where intrusive igneous rocks, such as granite, occur, their relations to the surrounding rocks should be carefully noted, and specimens at the contact of the two rocks collected. If altered sedimentary rocks are found these should be traced, if possible, away from the igneous rock until some indication of their age is obtained from included fossils. The distinction between a contemporaneous lava flow and an intrusive sheet of igneous rock is not always at first sight apparent; if the latter, it may pass from one bed to another or send tongues upwards into the overlying strata. Search should be made in the beds overlying the igneous rock for signs of alteration by heat. Thus limestone may be re-crystallised into marble, or shales altered into flinty hornstone.