There is a view of the town and harbor in the _Pennsylvania Mag._, June, 1773; and others of a later date are in the _Columbian Mag._, Dec., 1787; _Mass. Mag._, June, 1791. Cf. Winsor's _Readers' Handbook of the Amer. Rev._, p. 66, for other views and descriptions.] [Illustration: BOSTON CASTLE. After a photograph of a view in the British Museum.] Howe determined to attack the Heights by a front and flank assault. Washington reinforced Thomas, and planned at the same time to move on Boston by boats across the back bay. The British dropped down on transports to the Castle, but a long storm delayed the projected movement. This so effectually gave the Americans time to increase their defences that the British general saw that to evacuate the town was the least of all likely evils. As he began to show signs of such a movement, the Americans began to speculate upon their significance. Heath, at least, was fearful that the appearances were only a cloak to cover an intention to land suddenly somewhere between Cambridge and Squantum.[466] But the genuineness of Howe's intention gradually became apparent, as, indeed, evacuation with him was a necessity, while Admiral Shuldam also saw that his fleet, too, was immediately imperilled from the newly raised works on Dorchester Heights. So Howe had scarce an alternative but to give a tacit consent to a plan of the selectmen of Boston for him to leave the town uninjured, if his troops were suffered to embark undisturbed. Washington entered upon no formal agreement to that end, but acquiesced silently as Howe had done.[467] There was still some cannonading as Washington pushed his batteries nearer Boston on the Dorchester side, at Nook's Hill, teaching Howe the necessity of increased expedition. By early light on the 17th of March it was discovered that Howe had begun to embark his troops, and by nine o'clock the last boat had pushed off, completing a roll, including seamen, fit for duty, of about 11,000 men, with about a thousand refugees.[468] The Continentals were alert, and their advanced guards promptly entered the British works on the several sides. The enemy's ships fell down the harbor unmolested; but that night they blew up Castle William, and the vessels gathered together in Nantasket Roads. Here they remained for ten days, causing Washington not a little anxiety; and he wrote to Quincy, at Braintree, to have all the roads from the landings patrolled, lest the British should send spies into the country.[469] On the 27th, all but a few armed vessels, intended to warn off belated succor,[470] had disappeared in the direction of Halifax.[471] Ward was left with five regiments to hold the town and its neighborhood,[472] while Colonel Gridley, "whom I have been taught to view", said Washington, "as one of the greatest engineers of the age", was directed to fortify the sea approaches.[473] [Illustration: OCCUPATION OF BOSTON.