72 
HINTS TO TKAVELLEHS. 
Not unfreqiiently different rocks support different vegetation, and by 
noting the forms that are peculiar, the constitution of hills at a consider¬ 
able distance may be recognised. Thus some kinds of rock will be found 
tc support evergreen, others deciduous trees, others grass, whilst a fourth 
kind may be distinguished by the poverty or want of vegetation. It is 
not well to trust too much to such indications, but they may show which 
hills require examination and which do not. The form assumed by the 
outcrop of some hard beds is often characteristic, and may be recognised 
at a considerable distance. 
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 struc¬ 
turally 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 investi¬ 
gation 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. 
