Marilyn,
First of all,from what you posted, you did not say if you have a rifle or pistol. From your description, you have a firearm that was mfg.in England. The next question is it flintlock or percussion? On the hammer, does it have what looks like jaws with an adjustment to tighten it down. If it does, this is where a piece of flint is inserted & tightened down. It strikes a frizzen which is is hinged that covers a small pan where priming powder is placed. This would be a flintlock.
If it is percussion, the hammer when pulled back & fired, would strike a devise (called a nipple) that is small, round & with a whole in the center. A percussion cap would be placed on the nipple & when struck, would create a spark which would ignite the powder in the barrel. I know this sounds like Greek to a novice but if you describe it a bit more, most likely someone can help you more. From your description, I feel certain that your weapon is original.