Science & Nature

All that aside, the myrtle's most stunning attribute is its gorgeous cinnamon coloured bark, which peels away to reveal creamy white patches.

Earlier this month John Muratore, author of one of the documents acknowledged that even marshmallow-size pieces of insulating foam from the fuel tank could doom the space shuttle under the worst circumstances. He told reporters it is a risk NASA and the United States must accept for flights to resume anytime soon, and that it would take a total re-design of the tank to completely eliminate foam loss.

This particular one was introduced in 1752. It is huge and beautiful all year round for differing reasons. It is the first of all the maples to flower, which it does obligingly every March with hanging clusters of long-stalked, pale yellow flowers suspended beneath the opening bright green leaves, which later turn yellow to a pale orange, translucent in the autumn sunlight. This particular specimen is majestic against the winter skies.

It has a dizzying effect as you look up at it before rolling your head towards the West Stand and across the city of Dublin with its settlements of cranes. Soon they will be here amongst the suburban houses, tearing down our Tokyoesque West Stand branded by the DART running underneath, a nod to a brutal city that Dublin luckily never became.

It is a deciduous tree mainly planted for the shade it provides in cities, on the streets and in parks, and its resistance to heavy pollution levels – some experts claim it actually absorbs CO2 gases, but it is difficult to confirm this. At any rate its maple-shaped leaves (acerifolia) are shiny, causing the rain to run off them and so they don't absorb the pollution.

For several decades, astronomers had noticed irregularities in Uranus' orbit. These "perturbations" seemed to betray the gravitational pull of a distant, unseen neighbour. Then on 23 September 1846 Johann Gottfried Galle and his student Louis D'Arrest discovered Neptune at the Berlin Observatory. They were working on the basis of calculations made by the French mathematician Urbain Jean Joseph Le Verrier.

A spate of Catholic classical church building took place between the opening of the Pro-Cathedral (1825) and the Famine (1847). All the churches have artistic merit and express the competitive Catholic self-confidence of the time.

The first three are by different architects: St Francis Xavier, Gardiner St (John B Keane: 1829-32); St Nicholas of Myra, Francis St (John Leeson: 1829-34); St Andrew's, Westland Row (John Bolger: 1832-37).

Above the main road follow a byroad beyond houses and bungalows. Respect private property and privacy. Below the ridge, take the well-worn track up through the heather. Sticks or adjustable poles are useful in this terrain. There is a fairly steep climb through bushes, gorse, scree and rocks. On the shoulder, pause for breath and enjoy views over Dublin Bay: Bray, Killiney and Howth. The Cooleys and Mournes are visible on a clear day.

Essential advice from Póilín on home help and holiday homes

There's a good tea made from hawthorn and lime flowers, and the distinctive wine-red berrries, or haws, can be made into jelly or jam, as well as being an important source of food for birds in autumn and winter.