here

There is a Royal Plate version with less blur - catalogue.nli.ie/Record/vtls000319443 - which was used in this online book, 'Hutchinson's Britain Beautiful' Ed. Walter Hutchinson, 1920. See page 361 -
archive.org/details/hutchinsonsbrita01hutc/page/360/mode/2up

Which doesn't help with the date.

Not 100% sure this is the same bridge.
Looking 50 shades of green in June 2015 via Ed Maguire

I see it on the unlinkable 25" map, which is here on Google Maps, in what is now Dún a Rí Forest park.

Yes, there it is on the 6" too.

The NIAH was a reference to a Well at this spot, but the associated info is not online. No date for the bridge.

Class: Well

Townland: CABRA

Scheduled for inclusion in the next revision of the RMP: Yes

Description: The Archaeological Survey of Ireland (ASI) is in the process of providing information on all monuments on The Historic Environment Viewer (HEV). Currently the information for this record has not been uploaded. To access available information for research purposes please make an appointment in advance with the Archive Unit (open Fridays 10.00 am – 5.00 pm), Department of Culture, Heritage and the Gaeltacht, The Custom House, Dublin 1 D01W6XO or email nmarchive@chg.gov.ie.

No streetview of the bridge, but here is a photosphere nearby showing steps and a sign for Wishing Well

Awesome, no. Spiky spires decorative motif. South City Markets, Dublin. "the decent church that topt the neighbouring hill" spire, query.

Down Cathedral, Downpatrick Streetview

I suspect this is North of the border... I can't see it in buildingsofireland.ie...

Ninja'd! ...but not wrong!

Sharon Corbet Good job.