During my researches in mountain tracts, I have usually remarked, that the highest points of land either teem with life, or else are perfectly barren. My own experience would certainly tend to prove, that, in a general sense, one or the other of these extremes does almost constantly obtain. And, although I would not wish to dogmatize on phaenomena which may in reality be explicable on other hypotheses, it would perhaps be worth while to inquire whether the geological movements of subsidence and elevation will not afford some clew to the right interpretation of them. Be this, however, as it may, I can answer, that in many countries, where there are strong indications of the former, the alpine summits harbour an insect population to a singular extent; whilst in others, where the latter is as distinctly traceable, the upland ridges are comparatively untenanted. Now we have already shown, that where the gradual lowering of a region has taken place, there will be, of necessity, an undue accumulation of life on its loftiest pinnacles,--for, even allowing a certain number of species (which _even formerly_ were only just able to find a sufficient altitude for their development) to have perished, we shall have concentrated at that single elevation the residue of all those which have survived _from the ancient elevations above it_. But, if, on the other hand, an area, already peopled, be in parts greatly upheaved, there will be _either_ a universal dying-out, from the cold, of a large proportion of its inhabitants, or else an instinctive striving amongst them to desert the higher grounds on which they have been lifted up, and to descend to their normal altitudes: in both cases, however, the present summits will display the same feature,--namely, utter desolation.