In The Gallery at the top of the stairs in the south-east corner of NUI Galway's main quadrangle, the calendar seems to have slipped back to the year 1852.

The bewhiskered William King, first professor of geology and mineralogy at the college, would still feel at home here among the varnished oak display cases with their fossil, mineral and rock specimens.

For an annual salary of £200, he delivered 50 or more lectures each year, assisted research programmes and curated the geological collections. Virtually all of the specimens relating to King's famous monograph on the Permian fossils of north-eastern England reside here in the original Victorian display cases.

In effect, the James Mitchell Museum has, with the passing of 146 years, become a museum of a museum. An enthused Dr Martin Feely leads the way through the mineral collection. There is needle quartz from Brazil, a clump of ice-like spikes; natural diamonds from Zaire, disappointing to the lay eye; pyrite from Peru and purple amethyst from Brazil. One display mount is conspicuously empty where the native gold was removed by some enterprising but now-disappointed student, who had not advanced sufficiently in his studies to realise he would need a lot more gold than that small nugget to make his fortune.

Feely's favourite is silica, a very simple mineral, which lends itself to a diversity of beautiful forms and shapes - agates, amethyst, opal, onyx, bloodstone, smoky and clear quartz . . .

Minerals from close to home, including specimens from the old lead mines of county Galway which closed in the 1800s, form the basis of a local collection.

The Dave McDougall collection is a recent acquisition by the museum. An exploration geologist based in Oughterard in the early 1970s, he worked for a Canadian company and he was also a mineral collector. When he left Ireland, he donated his well-documented specimens to the museum. It is probably the most comprehensive collection of minerals from the Connemara region, Feely says.

And the rocks on display are only a selection from the hordes which throng the drawers beneath the cabinets. Dr Patrick Orr then takes up the tour, browsing through the palaeontology collection, under the watchful eye of a plesiosaur, a magnificent marine creature from Lyme Regis in the south of England. The plesiosaur is flanked by a German ichthyosaur. The current incumbent of the geology chair, Professor Paul Ryan, explains that the parish of Wurtenberg, in Germany, sold fossils and used the proceeds to help the poor.

Stopping at what look like scratched rock surfaces, Orr explains that this, in fact, is part of the Kiltorcan Devonian flora of Kilkenny, one of the earliest examples of a well preserved terrestrial flora . . . it's not just the pure abundance but also the quality, he adds, dismissing my scepticism about these unimpressive-looking objects.

Nearby, the fossil equivalents of modern ferns are beautiful in their detail.

In typical Victorian fashion, the early museum curators strove to collect one specimen from each taxon, casting the net widely to farflung places such as Brazil. "Today, we tend to focus more on local geology, ensuring that the specimens collected by staff and postgraduate students are properly curated," Orr says.

The whole lot was designated the James Mitchell Museum in 1977. Professor Mitchell was appointed to the chair of geology and mineralogy in 1921 and held this position until his retirement in 1966. An outstanding administrator, he was college secretary and registrar for 32 years.

The museum was not always in the pristine condition it now enjoys. Ironically, indifference during the time since King's tenure ensured the conservation of the museum and its contents in their original form. However, by the mid-1980s it was realised that, though, the main gallery itself was fine the collections and displays had suffered acute neglect.

The subsequent conservation efforts of the geology staff were ably assisted by FAS workers who participated in a three-year programme in the early 1990s to "restore the 19th century ambience" as well as to curate and conserve all of the material. The information was entered into a computerised database, the displays were refurbished and a museum book and information packs were published.

Leaving the museum, Professor William King's words on the plaque on the south-facing wall cross the centuries to inform us: "Geology treats of the (1) materials, intimate structure, order of position and origin of rocks, composing the crust of the globe (mineralogy, petrology & stratigraphy); (2) of the physical changes which the surface of the Earth has undergone and is now undergoing (physical geography); (3) and of the various plants and animals which have tenanted the lands and waters of bygone periods as well as the order of creation (palaeontology)."

The museum is open to the public, Ryan stresses, so feel free to wander into the grey limestone quadrangle, up the south-east stairs and view the specimens. School groups are advised to book in advance.

Further reading for the fascinated:

William King D.SC.: A Palaeontological Tribute , edited by David Harper and published by Galway University Press; An Irish geological time capsule: The James Mitchell Museum , edited by David Harper, published by the James Mitchell Museum