Talking of limestone brings to mind W. H. Auden's poem In Praise Of Limestone. He writes of ...rounded slopes/With their surface fragrance of thyme and, beneath,/A secret system of caves and conduits... and ...the springs/That spurt out everywhere with a chuckle,/Each filling a private pool for its fish and carving/Its own little ravine whose cliffs entertain/The butterfly and the lizard...

Auden (1907-1973) wrote the poem in May 1948 on the island of Ischia in the Bay of Naples. In it he celebrates the limestone landscape of the Mediterranean - which also recalls for him the karst topography of the Yorkshire Dales near his native English birthplace.

But this poem is not for the faint-hearted. Though memorable, its difficulty is challenging to say the least. Critics have given it many different interpretations - political, psychological, sexual, allegorical.

Auden seems to argue that Mediterranean civilization has, over time, built up layer upon layer like sedimentary beds of limestone; that Mediterranean culture is more sensual and hedonistic, yet also more religious and artistic, than the rationalist, Gothic, northern world; that the physical life of the body is just as important as the life of the spirit.

The English poet Stephen Spender (1909-1995) considered this poem one of the greatest poems of the 20th century.

The department of the Lot through which I was walking used to be the old French province of Quercy. Here a 1000 years ago, in the time of chivalry and the Chevaliers de la Table Ronde, troubadours sang their love songs in the language of Oc, the langue d'oc.

Then France was divided linguistically into 2 separate areas: the north with its langue d'oïl and the south with its langue d'oc, or Occitan, or Provençal (oc and oïl mean 'yes'). The northern langue d'oïl became the official French language of today because it was used by the court when Paris became the political centre of power.

Although the southern langue d'oc is no longer anybody's mother tongue, there has recently been a resurgence of interest in it, just as there has been in both the Breton and the Basque languages. Authors are writing books in it, and schools and universities are teaching it. This regionalism, I think, can only be a good thing. Anything that disrupts the homogeneity of so much of our modern life and culture is fine by me.

You can still see the old half-timbered houses of Quercy, their walls washed with limestone; and its dovecotes or pigeonniers (see photo), and its casselles, which are small, round, drystone-walled shelters for shepherds and wine growers. I passed many examples of all these as I made my way through this delightfully picturesque region.

This area was once an ancient sea. After a long period of geological time and upheaval, marine organisms stacked up on the sea bed and transformed into limestone rock, resulting in the limestone plateau or causse we now recognise. Since limestone is soft and porous, rivers like the Dordogne, the Tarn, the Lot and their tributaries scored deep fissures into this rock plateau, creating impressive gorges, canyons and ravines.