A prodigious task confronted him. The undisciplined and wretchedly clad swarm came and went as they chose, none having enlisted for more than a brief term. About 2,000 were sick or absent on furlough, out of a total of 16,771 soldiers. Several thousand more were needed to resist the attack that it was believed the enemy would soon make. But the British had received so severe treatment that it required weeks for them to recover, and the summer became oppressively hot. England recalled Gage, who sailed for home in October, and was succeeded by Howe. Washington closely besieged the enemy in Boston. Throwing up intrenchments, he steadily approached the city, and day by day and week by week the situation of Howe became more critical. When winter arrived, Washington formed the plan of crossing Charles River on the ice, but at a council of war the majority of officers declared the scheme too hazardous. Washington now decided to fortify and occupy Dorchester Heights, which would command the city and in a large degree the harbor. General Knox brought a number of cannon from Ticonderoga, that were dragged over the Green Mountains on sleds. Their arrival did much to cheer the spirits of the patriots, who numbered about 14,000. The commander called upon Massachusetts to furnish him with 6,000 militia, which was partly done. [Illustration: FANEUIL HALL, BOSTON, "THE CRADLE OF LIBERTY."] With a view of concealing his real purpose, Washington kept up a bombardment of the British lines throughout the nights of March 2, 3, and 4, 1776. On the night last named, General Thomas moved with 1,200 men from Roxbury and took possession undetected of the higher hill which commanded Nook's Hill, nearer the city. General Howe was amazed the next morning when he saw what had been done, for his position had become untenable. Preparations were made to embark men in boats and attack the Americans, but a violent storm prevented. Then it was agreed that but one thing could be done, and that was to evacuate Boston. The evacuation took place March 17th. The British destroyed a great deal of property, but left many supplies behind which fell into the hands of the Americans. Washington entered the city on the 19th, the main body of troops following the next day. The street through which he rode still bears his name. The Massachusetts Legislature voted their thanks to the great man, and Congress ordered a commemorative medal in gold and bronze to be struck. This medal is now in the possession of the Massachusetts Historical Society. When Howe sailed away, he took with him more than a thousand Tories, who dared not remain behind and meet their indignant countrymen. Instead of going to New York, as he originally intended, the British commander went to Halifax, where he waited for reinforcements and gave his thoughts to forming campaigns for the conquest of the colonies. DISASTROUS INVASION OF CANADA.