Its most probably a Snider, although most swing their breech-block to the right. I'll find a couple of good links for you and add them here soon. Feel free to 'Google' "Snider Rifle" in the meantime.

The maker is I. Hollis & Son by the way (for Isaac), rather than 'J', and the chambering is ".577 Snider". It was indeed Britain's first military breech-loader, although many sporters were made at the time, particularly by Hollis. Is yours a military or sporting pattern, dcmbsn?
Cheers

OK, here we go: check this LINK.

Here's a pic of the Snider action closed:

and open:

Hope this helps.