In 1829 Archer met Samuel Holland the owner of the Rhiwbryfdir slate mine at Blaenau Ffestiniog who was returning from Caernarfon.
Holland had travelled between Caernarfon and Penygroes on the horse drawn Nantlle Railway which was seeking a purchaser.
Archer became the managing director of the Ffestiniog company, and raised the initial capital of £24,185 largely on the Dublin Stock Exchange (including £11,905 of his own money).
Archer quarrelled with his fellow directors, the Oakeley Estate and with James Spooner and was less active in company affairs after the railway opened.
Following the successful Prince Consort Essay trials in 1853, he sold his copyright and patents to the Postmaster General for £4,000.