The snake in the top photo is a black racer (Coluber constrictor), non-venomous. The lower photo is of a cottonmouth (Agkistrodon piscivorus), venomous. Click on the photos to enlarge and take a good look at the eyes. The racer has a round pupil and the cottonmouth has an eliptical pupil. In my area of NC that is a sure way of telling a non-venomous snake from a venomous one. The only venomous snake in NC that has a round pupil is the eastern coral snake (Micrurus fulvius) and we are well north of its range here in the home swamp.