Our large map will, I hope, make clear and preclude the necessity of minutely describing the topography of the site with its surroundings far and near. What the basin of Lake Van and the plain of Mush are to the southern districts of Turkish Armenia, that are the plains of Pasin and Erzerum to those on the north. They represent depressions of the surface of the tableland and constitute arteries of communication between east and west. The northerly is separated from the southern string of depressions by a block of elevated plateau country, which is most compact and continuous on a line between Mush and Erzerum, and more broken into irregular lines of heights with intervening plains between the northern shore of Lake Van and Pasin. An invader coming from the east and desirous of forcing his way westwards will find all his roads converging on either one or other of the two strings of depressions. The block of lofty tableland, seared by the action of ice and water, and covered for the greater part of the year with snow, causes them to be deflected as by an impassable obstacle, though it is in fact by no means impervious to an army during summer, when the principal difficulty would be the absence of supplies. The geographical position of Russia is decisively in favour of an advance by the most northerly of the two main avenues. She might detach a column to move upon Bitlis; but the objective of this force would be the lowlands of Mesopotamia rather than Asia Minor west of the Euphrates. There can be little doubt that the weight of her onset would be thrown into the northerly channel; and Pasin would fall without a blow being struck. At that moment she would be confronted by the defences of the Deveh Boyun--an impregnable barrier if only held by a sufficient force.