The USS Signal was classified as a tinclad. I went to a site to find out some more on these ships.
A tinclad had tin nailed to its sides and became bullet-proof, but not cannon-proof. Being lightly-armored, they were of shallow draft and often used on reconnaissance duty up rivers.
Ironclads and tinclads, however, were not armored below the waterline and subject to great danger from Confederate torpedoes.
I'm finding out that naval ships on the rivers often did battle with Confederate soldiers on shore as well as made raids from the ships.
Now, I Know About Tinclads. --Old Blockade-Runner
