PROFESSOR Gemmel Morgan (May 5) persists with his question about why two figures are sometimes quoted by the SNP in reference to Scotland's economic surplus during the 18 years up to 1997. This has been explained on several occasions and specifically in The Herald's main news item of January 17, 1997, when the paper broke the news about Scotland's budget surplus.

I refer to it now. One figure was supplied by the Tory Chief Secretary to the Treasury, William Waldegrave, when he was cornered by persistent SNP questioning. It represents an absolute position and includes an estimate for Scotland's share of the UK deficit which, at 17.9%, is twice the country's population share. This estimate is, not surprisingly, disputed by the SNP.

The other figure which the SNP quotes is its own and represents a relative cross-border position. It ignores the disputed estimate. While it may be legitimate to argue about the exact value of these numbers it is not legitimate to claim, as Morgan does, that no explanation has been given or that the existence of two figures represents some kind of logical contradiction.

Morgan is right, however, to raise the issue of credibility. That Scotland had a surplus over the 18 years in question is not now in doubt since it is based on figures produced by the opponents of independence and includes the most pessimistic of estimates. Alternative figures may be produced by making alternative estimates but it was a surplus, not a deficit, and even Professor Morgan accepts that.

And that destroys, at least in my eyes, the credibility of all those spokesmen from all of the Unionist parties and from many academic institutions who, during that period, trotted out those dreary economic statistics telling us what hopeless cripples we were.

We know now that they were wrong. So why should we believe any of them when they tell us about our current position and make predictions about our future?

Hugh Noble,

Creachan, Portnacroish, Appin.

May 6.

JAMES Nelson in writing to defend the economic fictions of the SNP raises a fundamental problem that has yet to be answered by the nationalists (May 6). Claiming that ''the UK economy has consistently been run for the benefit of the south-east of England'' and that Gordon Brown is ''a Scot on the UK political make'' leaves a huge question-mark over the SNP's policy on European Monetary Union.

Alex Salmond and John Swinney attack Labour for setting interest rates to benefit Middle England while they themselves advocate a European Central Bank. Why are they happy for interest rates to be set for the good of Catalonia but not for the south-east of England? Surely this is a straightforward case of prejudice against the English? Does this make Alex Salmond the first in a long line of ''Scots on the EU political make''?

I look forward to some straight answers but doubt very much if I will get any.

Blair McDougall,

118 Main Street, Thornliebank. May 6.