Lieutenant-Colonel Coppee, of Philadelphia, volunteered his services to the State, and was sent to Altoona to arrange with the officers of the Pennsylvania Railroad Company for the defense of that point, the bridges crossing the Juniata, as well as the mountain passes, southerly toward Bedford, McConnellsburg, and London. Comparatively few troops offered for State defense . The President called for volunteers for sixth-months' service and Governor Curtin issued his proclamation for 50. 000 men . This was on the 15th, and men in masses began to assemble at Philadelphia, Harrisburg, Huntington, Altoona, &c. The militia of Pennsylvania was not organized . Farmers in the threatened parts were directed to remove their stock . On the 17th, the only company of infantry, Captain MCGowan's, from York Hospital, was sent to Shippensburg . Rebel advance fell back on the 18th to Greencastle . Some 2. 500 of General Milroy's force, in retreating, via Hancock, arrived near Bedford Springs, where their commander joined them . They were a good deal demoralized. Colonel Higgins re-enforced Milroy with 1. 200 men, without blankets or camp equipage . Militia regiments from New York began to arrive . New Jersey sent one regiment for the three days . Other companies from State reported at Harrisburg . The Secretary of War placed the arsenals and clothing depots at my disposal, also gave me ample authority to receive, subsist, and arm whatever troops might be offered from the neighboring States . The New York militia were mustered into the United States service for thirty days . The Pennsylvania generally declined to be mustered for six months. Finally a portion consented to serve during " the existence of the emergency . "The heights on the right bank of the Susquehanna, opposite to Harrisburg, were being fortified, in order to cover that city and the important bridges. Some of the patriotic citizens of that city volunteered to work in the trenches ; others were paid . The colored population were not behind their white brethren in giving assistance . The Eight and Seventy-first New York Militia went to Chambersbug on the 19th . Rebel advance of infantry and artillery 800 men, reported at Hagerstown . Brig. General W. F. Smith joined after returning from Altoona and Bedford. He was placed in command of all the troops and defenses opposite Harrisburg . The works were behind pushed under the chief engineer of the department, Captain J. B. Wheler, assisted by Major James Brady, First Pennsylvania Artillery ; Captain Wilson, of the Pennsylvania Railroad, and other employees of that and the Northern Central road. Every effort was made to organize artillery and get it into position. Major [Granville O.] Haller, acting aide-de-camp, was sent to Gettysburg to take command. Captain David McConaught, of Gettysburg, in company with others, were sent out scouts to gain information. Colonel Thomas, Twentieth Pennsylvania Volunteers, hat the defence of the bridges of the Northern Central Railroad. On the evening of the 22d, the rebel cavalry advanced upon Chambersburg, followed by heavy masses of infantry and artillery . It was the head of their army, under General Lee. A part of Ewell's corps advanced toward Carlisle, which place they occupied on the 27th and