From men in hats to an immovable object - the Poolbeg Lighthouse in Dublin Bay from the wonderful Eblana Collection. Looking at the building one can see a megaphone type thingy (technical description based on Carol's guidance) which was used to wake those residents who lived nearby?
Collection: Eblana Photograph Collection
Date: Catalogue range c.1870-1890
NLI Ref: EB_1466
You can also view this image, and many thousands of others, on the NLI’s catalogue at catalogue.nli.ie
Owner: National Library of Ireland on The Commons
Source: Flickr Commons