MAFEKING.--Protectorate Regiment (800), Cape Mounted Police, British South Africa Company's Mounted Police, Bechuanaland Rifles--1500 men. COLONEL PLUMER'S FORCE.--Rhodesia Regiment, Southern Rhodesia Volunteers, Bechuanaland Border Police, A Detachment of Canadian Artillery. COLONEL MAHON'S FLYING COLUMN.--100 men from Barton's Frontier Brigade, 200 Queenslanders (Bushmen). KIMBERLEY MOUNTED CORPS.--Diamond Fields Horse, Kimberley Light Horse, Cape Police, Imperial Light Horse, Diamond Fields Artillery, M Battery Royal Horse Artillery--1200 men. ON THE WESTERN FRONTIER--THE INVASION OF THE TRANSVAAL _VIA_ CHRISTIANA. At the same time, on the Western Frontier, affairs were progressing in accord with Lord Roberts's strategical programme. Sir Charles Warren had arrived to take up his new post as military governor of Griqualand West, and General Hunter was engaged in a species of overture to cover the advance of the Flying Column which had started on the 5th. Without opposition he effected the passage of the Vaal River at Windsorton. There was great satisfaction to feel that British shells were at last exploding in Transvaal territory, and that the voice of the new gun, "Bobs," was spreading devastation far and wide. Three Boer laagers were dispersed, and on the 4th of May the new weapon caused considerable commotion within the Republican border. Ambulances were seen performing their melancholy duty for some time after the morning shelling had ceased. On the 5th Barton's Brigade encountered 2000 and more of the enemy some two miles north of Rooidam. The Dutchmen held a hilly and jungly position extending over four miles, but from their beloved kopjes they were routed time after time, and with considerable loss, by the magnificent dash of the troops, who carried one ridge after another with splendid energy and daring. The Yeomanry under Colonel Meyrick especially distinguished themselves, their courage and coolness under fire being remarkable. They not only engaged the enemy at very close quarters, but chased them for miles. General Hunter, having settled the Dutchmen, after a contest of some eight hours' duration, joined hands with the British force under General Paget at Warrenton.