In spite of their victory, the British at Mackinac were very short of provisions and would starve if they were not resupplied before Lake Huron froze at the start of winter. Sinclair had earlier captured a small schooner (
Mink) belonging to the Canadian North West Company, and learned from one of the prisoners that the British supply base was at
Nottawasaga Bay. Having sent
Lawrence and
Caledonia back to Detroit with the militia, he arrived at the Nottawasaga with
Niagara,
Scorpion and
Tigress on 13 August. The British detachment at Nottawasaga consisted of a
midshipman and 21 sailors of the
Royal Navy under Lieutenant
Miller Worsley, and 9 French Canadian . The schooner
HMS Nancy was present at the Nottawasaga, loaded with 300 barrels of provisions (salted pork, flour, spirits etc.) for the garrison at Mackinac. A few days before the Americans appeared, Lieutenant
Robert Livingston of the
Indian Department had arrived, carrying a warning from Lieutenant Colonel
Robert McDouall, the commandant at Mackinac, of the American presence.
Nancy was towed up the
Nottawasaga River, and a crude
blockhouse armed with two 24-pounder
carronades removed from
Nancy and a 6-pounder field gun was hastily constructed for her protection. Livingston had proceeded onwards to York to request reinforcements, but none were available. (Almost all the British regular troops in
Upper Canada were already engaged in the
Siege of Fort Erie, and the militia could not be persuaded to turn out.) On his return, Livingston was able to gather 23
Ojibwa to help Worsley's party. The Americans believed that
Nancy was still
en route to the Nottawasaga and intended to intercept the schooner on the lake, but on 14 August some of Croghan's troops landed to set up an encampment on the spit of land at the mouth of the river and foraging parties chanced on the schooner's hiding place. The next day, Croghan's troops (three companies of regular infantry) landed and attacked. The American vessels opened fire over intervening sand hills without success, but the Americans then landed a detachment of artillery with one (or two) 5.5-inch
howitzers to support the infantry. Worsley decided that further defence was impossible and made preparations to destroy the blockhouse and schooner. A line of powder was set running to
Nancy and from there to the blockhouse. At four o'clock,
Nancy was set alight which in turn by way of the powder train, set off an explosion in the blockhouse. The blockhouse explosion surprised Sinclair, causing him to think that one of the howitzer's shots had found its mark. Worsley's party then retreated into the woods, having suffered one killed and one wounded. The Americans recovered the guns from the wrecked blockhouse and then felled trees across the river to block it. Sinclair departed for Detroit in
Niagara, leaving the gunboats under Lieutenant
Daniel Turner to maintain a blockade of the bay. Sinclair's orders were that the gunboats were to remain until they were driven from the Lake by bad weather in October, by which time it would be impossible for small boats to re-establish communications between the Nottawasaga and Mackinac. He did however authorize
Tigress to cruise for a week or two around St. Joseph Island to intercept fur canoes. The gunboats' crews were reinforced by twenty-five men of the 17th U.S. Infantry, to serve as
marines. ==Movements in late August==