Secret intelligence hurried forward the project. General Gage, it was said, intended to take possession of Dorchester Heights on the night of the 18th of June. These heights lay on the opposite side of Boston, and the committee were ignorant of their localities. Those on Charlestown Neck, being near at hand, had some time before been reconnoitered by Colonel Richard Gridley, and other of the engineers. It was determined to seize and fortify these heights on the night of Friday, the 16th of June, in anticipation of the movement of General Gage. Troops were draughted for the purpose from the Massachusetts regiments of Colonels Prescott, Frye and Bridges. There was also a fatigue party of about two hundred men from Putnam's Connecticut troops, led by his favorite officer, Captain Knowlton; together with a company of forty-nine artillery men, with two field-pieces, commanded by Captain Samuel Gridley. A little before sunset the troops, about twelve hundred in all, assembled on the common, in front of General Ward's quarters. They came provided with packs, blankets and provisions for four-and-twenty hours, but ignorant of the object of the expedition. Being all paraded, prayers were offered up by the reverend President Langdon, of Harvard College; after which they all set forward on their silent march. Colonel Prescott, from his experience in military matters, and his being an officer in the Massachusetts line, had been chosen by General Ward to conduct the enterprise. His written orders were to fortify Bunker's Hill, and defend the works until he should be relieved. Colonel Richard Gridley, the chief engineer, who had likewise served in the French war, was to accompany him and plan the fortifications. It was understood that reinforcements and refreshments would be sent to the fatigue party in the morning. The detachment left Cambridge about 9 o'clock, Colonel Prescott taking the lead, preceded by two sergeants with dark lanterns. At Charlestown Neck they were joined by Major Brooks, of Bridges' regiment, and General Putnam; and here were the waggons laden with intrenching tools, which first gave the men an indication of the nature of the enterprise. Charlestown Neck is a narrow isthmus, connecting the peninsula with the main land; having the Mystic River, about half a mile wide, on the north, and a large embayment of Charles River on the south or right side. It was now necessary to proceed with the utmost caution, for they were coming on ground over which the British kept jealous watch. They had erected a battery at Boston on Copp's Hill, immediately opposite to Charlestown. Five of their vessels of war were stationed so as to bear upon the peninsula from different directions, and the guns of one of them swept the isthmus, or narrow neck just mentioned.