Preparations were made with great secrecy. Boats for the transportation of the troops were launched, and moored under the sterns of the men-of-war. Grenadiers and light infantry were relieved from duty, and held in readiness. On the 18th, officers were stationed on the roads leading from Boston, to prevent any intelligence of the expedition getting into the country. At night orders were issued by General Gage that no person should leave the town. About ten o'clock, from eight to nine hundred men, grenadiers, light infantry, and marines, commanded by Lieutenant-colonel Smith, embarked in the boats at the foot of Boston Common, and crossed to Lechmere Point, in Cambridge, whence they were to march silently, and without beat of drum, to the place of destination. The measures of General Gage had not been shrouded in all the secrecy he imagined. Mystery often defeats itself by the suspicions it awakens. Dr. Joseph Warren, one of the committee of safety, had observed the preparatory disposition of the boats and troops, and surmised some sinister intention. He sent notice of these movements to John Hancock and Samuel Adams, both members of the provincial Congress, but at that time privately sojourning with a friend at Lexington. A design on the magazine at Concord was suspected, and the committee of safety ordered that the cannon collected there should be secreted, and part of the stores removed. On the night of the 18th, Dr. Warren sent off two messengers by different routes to give the alarm that the king's troops were actually sallying forth. The messengers got out of Boston just before the order of General Gage went into effect, to prevent any one from leaving the town. About the same time a lantern was hung out of an upper window of the north church, in the direction of Charlestown. This was a preconcerted signal to the patriots of that place, who instantly despatched swift messengers to rouse the country. In the mean time, Colonel Smith set out on his nocturnal march from Lechmere Point by an unfrequented path across marshes, where at times the troops had to wade through water. He had proceeded but a few miles when alarm guns, booming through the night air, and the clang of village bells, showed that the news of his approach was travelling before him, and the people were rising. He now sent back to General Gage for a reinforcement, while Major Pitcairne was detached with six companies to press forward, and secure the bridges at Concord.