Silvanus Cobb (Sylvanus Cobb) (b. Plymouth, New England in 1709 - d. Havana, 1762 ) was a Massachusetts provincial army captain and later naval commander who fought for the British primarily in Nova Scotia in the 1740s and 1750s.
During King George's War, Cobb was commissioned captain of a company in Col. Shubael Gorham's 7th Massachusetts provincial infantry regiment, also known as "the whaleboat regiment" because so many of its members were employed in the Cape Cod / Nantucket whaling industry and because of the whaleboats the regiment used during water-borne operations. The force was recruited from among the populations of Plymouth, Barnstable and Bristol counties in southeastern Massachusetts in 1745 for the Expedition against Louisbourg. Gorham's regiment made up the majority of men who attacked the island battery in Louisbourg Harbor during the siege—suffering significant casualties in a series of failed amphibious assaults. Cobb probably took part in some or all of these attacks. He later commanded another provincial company stationed at the Annapolis Royal garrison at Fort Anne in Nova Scotia in 1746-47, and was later captain of a small armed vessel based there. The vessel was employed by the British government to cruise in the Bay of Fundy in 1747-48. The vessel was also often used as a transport and support vessel for Gorham's Rangers.
During Father Le Loutre's War, after the establishment of the Government in Chebucto in 1749. Cobb's vessel became part of Captain John Rous's sea militia which helped keep open communications along the coast of Nova Scotia and with New England. Governor Edward Cornwallis described Cobb as a settler who "knows every Harbour and every Creek in the Bay [of Fundy], a man fit for any bold enterprise." Cobb's vessel was employed in taking troops and supplies to Fort Anne (Annapolis Royal), Fort Edward (Windsor), Fort Lawrence (near Amherst), and the Saint John River, and in convoying transports which carried German settlers to found the town of Lunenburg in 1753. In the winters of 1753, 1754, 1755, and 1756 he was ordered to Chignecto with stores for the garrison and remained there each year till spring. Cobb had a house and farm near Fort Lawrence where he lived with his wife and daughter.
In April 1755, while searching for a wrecked vessel at Port La Tour, Cobb discovered the French schooner Marguerite (Margarett), laden with provisions, guns, and other military stores from Louisbourg destined for French troops on the Saint John River. He returned to Halifax with the news and was ordered by Governor Charles Lawrence to blockade the harbour until Captain William Kensey (MacKenzie?) arrived in the warship Vulture, and then to assist Kensey in capturing the French prize.