What have Sunday's Well in Clane, St. Peter's Well in Donadea and St. Patrick's Well at Ardrass got in common? They are all thermal or warm springs. The temperature at Clane is 13 degrees Celsius or 3 degrees above normal. There are ten such springs known in the country and eight of them are in north Kildare or south Meath. The other two are at Mallow and Dunlavin. They are all associated with saints and are places of pattern or pilgrimage. Each has a strong outflow which responds to the cycle of the moon as do the tides. They emit bubbles. Each lies in a straight line with a number of other warm springs and are generally three or four miles apart. Practically all are associated with sand-hills. Sunday's Well, is behind the Motte at the Liffey Bridge, and lies at the intersection of two straight lines connecting eight warm springs. One runs north-east and connects Sunday's Well, St. Patrick's Well at St. Patrick's Hill on the way to Celbridge, the spa Well at Lousia Bridge in Leixlip and St. Margaret's Well in north County Dublin. The intersecting line runs north west and connects Sunday's Well to St. Peter's in Donadea, Dysert on the road to Johnstownbridge, Killbrook, to the west of Enfield and Hotwell House near Longwood.

Practically all have associated sand-hills. That in Clane is, of course, the Motte, re-fashioned slightly from a pre-existing hill in medieval times. The natural stratification of the sand can be seen following a brush with a JCB in the '70s. St. Patrick's Hill dominates the horizon once you pass Barberstown Castle on the way to Celbridge. The well is just off the roadside at the highest northerly end of the hill. St. Peter's Well is accessioned by turning left at the Range, a small crossroads at the north-west corner of Donadea Demesne on the road from Prosperous to Ballagh Cross. It is beside a steep sand-hill at Dunmurahil (now almost completely quarried), where St. Patrick is reputed to have built a church.

Dysert, where there is also an accompanying sand-hill, is reputed to mean desert and is common in place names, indicating early Christian hermitages. The springs at Killbrook and Longwood are unusual in that they do not have the patronage of a saint and that both (?) appear to have been discovered as a result of quarrying or drilling. That at Killbrook was discovered in the mid nineteenth century during the building of the railway near Enfield. Gravel was being excavated for this purpose from a massive shapeless sand-hill when the workers were surprised to find steam rising on a cold winter's day! This was the warmest well in Ireland, with a temperature of 23 degrees Celsius or 73.5 degrees Fahrenheit. It is not up to Icelandic geyser standards but it is none the less remarkable. That at Longwood has neither hill nor saint and appears to have been the result of drilling. Further drilling in recent years, by some hundreds of feet, is reputed to have raised its temperature dramatically and it is used to meet all the hot water and heating requirements of the farmer. The Spa Well at Leixlip lies in the deeply scoured valley of the Rye River and it is not surprising therefore that it has not an accompanying sand-hill. It hasn't got a saint but spas were the subject of visitations of a different kind.

The geological explanation for thermal springs is that they are associated with synclinal folds extending, like valleys, deep down into the rock which forms the earth's crust. They may be thousands of feet deep. They were formed in ancient seas the carboniferous or limestone period and were in due course filled with the usual horizontally stratified limestone. Because limestone is such a water permeable rock these deep folds allow the water to make contact with warmer rock at great depths. As a result of this warming at a great depth, cyclic convection currents on a huge scale are set up with warm water rising at three to four mile intervals and cold water descending to replace it at centres in between.

A possible explanation for the sand-hills accompanying these warm springs is that during the ice-age the warm water was active under the ice at these points and caused local melting and deposition of the load of sand and gravel which was carried by the ice. The sand-hills concerned are generally higher at one end and taper off in the direction of the out-fall. St. Patrick's Hill is a remarkable example.

It must have been a matter of great wonderment to our pre-Christian ancestors to find a well that never froze in winter and was associated with a hill rising dramatically from an otherwise flat landscape. The well was sometimes, like at Brideswell north of Kilcock, on top of the hill. Early Christians blessed such wells and adapted existing practices associated with them.

Reproduced from "Le Chéile" by kind permission