As this narrative purposes so to present the geography of the Philippine Islands as to facilitate an easy remembrance of the essentials only of the governmental problem there presented, we will hereafter speak of the First District as containing, roughly, 6500 square miles, and 650,000 people. Whenever, if ever, a Philippine republic is set up, these six provinces are very likely, for geographical and other reasons, to become one of the original states comprising that republic, just as the states of Mexico are made up of groups of provinces. [280] The rest of the story of the northern campaign of 1899-1900 immediately following Aguinaldo's escape into the mountains through General Young's and General Lawton's lines, being a necessary part of the American occupation of the Philippines, may also serve as a text for further acquainting the reader with the geography of Luzon. War is the best possible teacher of geography, and it may be well to communicate in broken doses, as we received them, the lessons on the subject which the 8th Army Corps learned in 1899 and the subsequent years so thoroughly that we could all pronounce with astonishing glibness, the most unpronounceable names imaginable. When the great Wheaton-Lawton-MacArthur "Round-up" reached the mountains on the northeast of the great central plain, in the latter part of November 1899, Captain Joseph B. Batchelor, with one battalion of the 24th (negro) Infantry, and some scouts under Lieutenant Castner, a very intrepid and tireless officer, boldly cut loose from the column of which he was a part, and, pressing on over the Caranglan pass, overran the province of Nueva Vizcaya, which is part of the watershed of north central Luzon, proceeding from Bayombong, the capital of Nueva Vizcaya, down the valley of the Magat River, by the same route Messrs. Wilcox and Sargent of the navy had made their pleasant junket in the fall of 1898 as described in Chapter VI (ante). Following this route Captain Batchelor finally came into Isabela province, where the Magat empties into the Cagayan River, reaching Iligan, the capital of Isabela, ninety miles northeast of Bayombong, about December 8th. From Iligan Batchelor went on, promptly overcoming all resistance offered, down the great Cagayan valley, some 110 miles due north, to the sea at Aparri, the northernmost town of Luzon and of the archipelago, where he met two vessels of our navy, the Newark and the Helena, under Captain McCalla, and found, to his inexpressible (but partially and rather fervently expressed) chagrin, that the insurgents who had fled before him, and also the garrison at Aparri, had already surrendered to the navy. The territory thus covered by Batchelor's bold, brilliant, and memorable march over two hundred miles of hostile country from the mountains of central Luzon down the Cagayan valley to the northern end of the island, at Aparri, [281] consisted of the three provinces of Cagayan, Isabela, and Nueva Vizcaya.