Why Ireland stays split North and South

Several days ago, the Provisional Irish Republican Army (IRA) bombed the railway line between Belfast and Dublin.

This line connecting the North and the South has been bombed many times since the current troubles began in 1969. Repairs are made quickly and the trains are normally running again within a day or two. The periodic fracture of the link is deplored by political and public spokesmen in both parts of Ireland who oppose terrorism.

But the physical break in communication along the rail line is symbolic of a deeper rift between North and South.

At the moment, relationships are cool. The North's 1 million Protestants resist all political overtures from the South. They argue that the South's constitution favors the republic's mainly Roman Catholic population.

Southern politicians claim that Northerners would be welcomed in united Ireland and that their presence would create changes to take account of Protestant views. They say these would include new legislation on divorce, which is prohibited in the South, and contraception, which is less freely available than in the North.

But there is no sign of a break in the North-South political deadlock. For example, the republic's present government intends to hold a referendum on abortion that Protestants believe would consolidate the anti-abortion lobby in the South. Southerners, meanwhile, feel that Northern Unionists remain unreasonable about sharing political power with Catholics in the North.

Cross-border security remains a controversial problem. Northerners accuse the republic of providing a haven for IRA terrorists. The Rev. Ian Paisley, leader of the North's Democratic Unionists, likened the situation to the Middle East.

He said on July 12: ''If Ulster was ruled by the Israelis, and the PLO's equivalent and friends - the IRA - continued their cross-border attacks on our people and province, then most certainly there would be raids as far south as Cork.''

Southerners bitterly resent accusations that they are not firm enough with terrorists. They point to the large number of police and Army on border duty and to the huge cost of this operation. More recently Dublin sources have underlined the effectiveness of cross-border laws, which can be used to apprehend people and make them stand trial for offences allegedly committed either in Northern Ireland, the Republic, or the British mainland.

On July 13 legal history was made when Gerard Tuite was sentenced to 10 years in jail in Dublin for possessing explosives in London. This was the first time that an Irishman was convicted in Dublin for an offence committed in England.

Afterwards a Dublin government spokesman said he hoped that this would reduce the accusations by Unionists. But Jim Allister of the Democratic Unionists in Belfast claimed that the republic showed no signs of dealing with other ''wanted'' terrorists within its borders. He claimed that this could only be done by ''proper extradition,'' that is by handing over suspects to stand trial in the North.

So far the republic has declined to do this. Southerners claim that extradition of suspects, who could claim a political motive for their alleged actions, would raise complex constitutional problems. So, despite the existing cross-border legislation, the north-South deadlock remains because of security and extradition issues.

There have been some positive signs. The republic has agreed to provide natural gas at a competitive price to the North's hard-hit gas industry. The Irish Premier Charles Haughey has been sympathetic toward providing a possible order for Belfast's ailing shipbuilding industry. And he has intervened to try to persuade the European Community to provide some much needed money to improve Belfast's housing. Yet these hopeful signs are outweighed by Northern suspicions of not only the republic but of Mr. Haughey himself.

He has long been regarded in the North as a hard-line Republican. Recently his failure to back Britain in the Falklands crisis have further incensed his Unionist critics. Relations between Britain and Ireland are said to be chilly in the Falklands aftermath. A further meeting between England's Margaret Thatcher and Haughey, has not been scheduled.

Haughey, with not a little Irish whimsy, said that as Britain had been preoccupied with the Falklands ''to put it mildly,'' he had not deemed it appropriate to ask for a summit meeting. In plain terms that means that the Irish border, and the resultant North-South rift, is more rather than less entrenched after the events of recent weeks.