Hello!

This gentleman wears a Rifle Volunteer uniform- Unfortunately, which volunteer regiment he was a part of is a bit difficult to determine. The device on his cap (in the right of the photograph) bears a recognizable light infantry bugle horn, but the device beneath it is obscure. The same goes for his pouch belt (worn over the left shoulder), which, if it did bear a regimental bade, is now obscure.

Rank, too, is difficult to discern. During this period, from 1855-1880, British officers wore rank insignia on their collars. Senior officers wore trim all around the collar. Colonels were distinguished by a crown and star, lieutenant colonels a crown, and majors a star. Junior officers wore trim only on the top of the collar- But followed the senior officers in badges of rank. Thus, captains wore a crown and star, lieutenants a crown, and subalterns a star. I am more prepared to make a judgement as to the rank of the gentleman. Though obscure, he appears to wear a crown on his collar, marking him either as a lieutenant-colonel or a lieutenant. I am inclined towards the latter, as the placement of the insignia seems to be towards the bottom edge of the collar.

Now, on to what we do know: He wears a style of tunic popular amongst volunteer regiments, as seen on these rifle volunteers, c. 1860, members of the Victoria Rifles, and on the far left of this print of a Scottish volunteer review. For good measure, here's a modern depiction of a member of the picturesquely named 'Robin Hood Rifles', c. 1865, by the military artist Bill Younghusband. The coat's braided front and black trim, owes much to contemporary uniforms of the Rifle Brigade in the regular army, as does the black leather equipment and whistle. However, the coat on the gentleman in the photograph, and on the volunteers in the images above, is cut more along the lines of contemporary shooting frock coat than a military tunic. The rifle volunteers were militia associations formed in 1859, during one of Britain's periodic French invasion scares.

I hope that helps. Unfortunately, distressingly little has been written as regards the dress of the innumerable volunteer regiments, so I at the moment I cannot recommend a text for further reading. If you have any questions, feel free to ask and I'll do my best to answer.

Edit: I should also add that the fit of his coat, particularly the voluminous sleeves, appears to date the picture from some time in the 1860's.