A sketch of the unfortunate and unhappy accidents that happened on board the Egmont : By the bursting of two of her guns, on the 10th and 19th of June, 1777. With observations on the difference of metal made with pit-coal and charcoal; intended as a directory to merchant ships, letters of marque, &c. fitting out with guns at this important crisis. By John Law M'Clellan, surgeon of His Majesty's Ship Egmont.