cybertect
It's grim up north (London)
Well, packhorses bridges wree built for centuries so it's hard to pinpoint what century it was built in. I've found stone packhorse bridges built in the 1500s and ones built a couple of hundred years later looking very similar. Maybe Cybertect can tell us if construction changed dramatically at any time, but as Cybertect seems to be ignoring anything I say...!
I think we should send Cybertect out with a camera and tell her to get up off her arse and find the answer
Well, if you will insist on calling me 'she'...
I'm not supremely well versed in the changes in construction techniques for small bridges, but I would suspect that the one in the photo dates from before the advent of the railways in the 1840s. After that, brick would likely have taken over from stone.
Before that, for small structures like this, they were liable to use traditional techniques that changed little over the centuries. Engineers like Thomas Telford were the first to start applying modern thinking to bridge design at the end of the 18th century.
Could have been on holiday or on some assignment?
FWIW, for most people, taking a holiday is itself fairly unlikely in the 19th century.
Taking a full plate camera (with tripod, etc.) with you on holiday is highly unlikely, especially if you were still using wet plate technology which meant literally carting a laboratory around with you in a van, like this one used by Roger Fenton in the Crimea.
There was a very brief window of opportunity between preparing the plate with chemicals, taking the photograph and then developing and fixing the image.
mick's already mentioned that the bridge image is a wet plate negative.*
If it was further afield, then some kind of commission or project would be a more likely reason for that.
* e2a: Dry plate technology, which was developed in Britain in the 1870s, enormously opened up the opportunities for photographing further afield with more lightweight equipment.