Between the recently conquered provinces of Russia and our empire of India lies the mountainous country of Afghanistan, inhabited by warlike tribes of brave, fanatical Mohammedans who certainly have no love for Russia. In a geographical and indeed in every sense, it is laid out, as it were, as the natural frontier of an empire. All along its northern provinces stands the snow-capped range of the Hindoo Koosh, stretching away from east to west: a line of mountains between 15,000 and 20,000 feet high, with few practicable passes, and even these are closed in winter. It thus presents for the greater part of its length a natural barrier against aggression, which a few military works at the passes would render impregnable. Even as far west as Herat, the ranges to the north of it are several thousand feet high. But this is not all. The great ridges which run away in a south-westerly direction from the Hindoo Koosh, and which, enclosing long narrow valleys of limited fertility, form the greater part of Afghanistan--all these present a series of additional natural defences. Afghanistan resembles Switzerland, but its mountains are higher, its defiles more difficult, its resources very scanty, and it has no roads properly so called; so that an enemy advancing from the north can only come in any force by one route--that is, by skirting the successive ridges where they sink into the southern deserts. It is indeed remarkable that India is surrounded for hundreds of miles to the north-west by a vast zone of barren country, including Afghanistan, Persia, and the principalities; territories unequalled perhaps in the world for their misery and desolation; but which, regarded from a purely military point of view, offer a great impediment to projects of invasion. The Afghans are poor, but brave, hardy, fanatical, and no doubt somewhat turbulent. They hate all intruders. In former days the hordes of Asia, composed chiefly of cavalry, could disregard bases of support and supply, and, being unencumbered with siege trains or other modern appliances, could sally out from these desert wastes, and, braving all risks, overflow the comparatively rich fertile plains of India. But all such incursions are now happily impossible. Circumstances have entirely altered. Modern science has so expanded the means of defence that armies of invasion must necessarily bring with them a corresponding power; and this entails vast encumbrances, numerous depôts, good roads, and safe communications.