A letter was received on Saturday from Huron, in Ohio, by the Express Mail, from the Post Office Agent, announcing that the express mail had not been able to approach Fort Meigs in consequence of hearing on its approach an incessant firing of cannon and small arms. It was first heard on Sandusky on Friday, the 30th April, and continued firing at the time the Express came away. The firing had ceased once, from which it is presumed that the enemy had returned to the attack after being once repulsed. Some persons had gone within two miles of the Fort, and one ventured within half a mile, and so near, as distinctly to see the flash of the cannon through the trees. The number of the enemy is not known. We wait with extreme anxiety for Wednesday's Express Mail, though we have no fears for the result, as letters have been received here from Fort Meigs as late as the 25th April, at which time no apprehensions were entertained for the result of any attack.