THE SUN is weakening now, and prudent sons of men sit by the fire to await the passing. Only the ermines (odd Nordic beasts) bounce out to see what's up - they and those whose attention spans are short either grief or hibernation.

Thus fortified with high sentiments, I ventured over to the Finnish ambassador's house where they were celebrating their national day of independence.

The new ambassador, Jaakko Iloniemi, is a trim, muscular man, as I feared, capable of cracking ice in the swimming pool as his predecessor did. Suitably ungarbed, the Finns leap out of the sauna with a shout and dive in. But they have not been icing it up this year, yet.

The warmblooded Fulbrights (J. William Fulbright was long the Democratic senator from sunny Arkansas) were there along with Soviet ambassador Anatoliy Dobrinin and Mrs. Dobrinin from the land of bear.

The man at the door haled and heartfelt the world coming up the steps and saw no reason to keep the door shut on so mild an evening, it being well above 10 below.

You could see your breath in the entrance hall and it was not worth seeing. Once inside you could stand in a sheltered corner and wait, like a numb leopard, for the hot meat pastries to come by on platters.

Hibernation is, of course, the true answer, but the Finns, if they want a suggestion, could shift the sauna right up to the entrance hall and shut the front door.

We once had a tropical tortoise, Pilgrim, who did not hibernate and required to be kept at 80 degrees all winter. Those wee exciting years. I never left his room.

There is a Washington tortoise, Toto, who does hibernate, and who presents, I believe, one of the knottiest problems I ever heard of:

His owners, A1 and Jill Gollin, have abandoned this capital and moved to one of those high towers in New York to live.

Peopel knew the Gollins had friends, and sorrowed right along with them because moving farther north is a sad thing.

But people never knew the true crisis, which was what to do with Toto. He is a Greek tortoise (which does not come from Greece, really, but from southern Spain and northern Africa) of the same sort Archbishop Laud had at Lambeth Palace, where the animal lived for a century until accidentally stabbed by a gardener with a spading fork while hibernating in the palace garden. (The shell, as everybody knows, is still at Lambeth and the incumbent archbishop will allow it to be exammed, if one is a serious friend of the tortoise.)

And Napoleon's tortoise, the one he was so fond of at Elba, lived well into our own century, which I mention to remind us that tortoises can live a century or so, and the possession of a tortoise is a responsibility you do not trifle with.

The Golins' tortoise is 50 years old and was inherited from Jill Gollin's father, a Swiss with interesting connections to the chocolate industry, though the Gollins are all slender.

When Jill was a tot the question was faced squarely, who should inherit the tortoise at the father's death? It was decided, all those years ago, that Toto should go to the child who first married and had a child to reach the age of 3.

It sounds complicated. But you do not pass on your tortoise casually - you want somebody steady, the sort who settles down and has kids and raises them up.

Do not imagine that life was all strawberries with the Gollins, merely because they inherited the tortoise years ago.

They lived for a time in New York, in an apartment. When hibernation time came in October, Toto was put in a box and bedded down until April. They kept him out on the fire escape ("a least we had a fire escape back then," said Jill Gollin in an understandable burst of self-pity) but on very cold nights they brought the box in.

It was tricky keeping Toto cold enough to stay dormant, but not cold enough to freeze. But they managed.

Then they moved here, and it was paradise for the tortoise. He roamed the garden in summer, a nip of violet here a crunch of lily there and his hibernations were never better, never safer, never less trouble, than in the basement right here in our city.

But now New York again. Not even a fire escape this time. No basement. No nothing. In that high tower there is no room - not a balcony even for the beast. No room at the inn, the old, old story.

Few things have concerned me more in recent weeks than the issue of the Gollin heights and the legitimate rights of this humble member of the Gollin family. He was a legal inheritance and he certainly is a responsibility the Gollins cannot just ignore, and besides they must think of the future, for the first of their own children to have a chil that reaches the age of 3 will inherit Toto when Al and Jill are gone.

If you have a tortoise you do not dodge hard facts, and you pass the legacy on. It would be a hard thing to say when your life is reviewed, "I did not pass it on."

The Gollins, you may be sure, have been in a regular storm about what is best to do.

Toto is bedded down for the winter, right here in our city, which is so much better for tortoises than Gotham can ever be, under a temporary curator. The Gollins will pick Toto up when he comes to, in the spring, and take him to New York. As for next winter, who knows?

If the heart is right, if the crisis is faced squarely, and if the past has given any grounds at all for faith, then the possessor of an ancestral tortoise may proceed with hope knowing that however grim the facts, how seemingly blocked the avenues may be, still a way will be found. Too much is at stake to run around flinging arms up. Though there may not be even a fire escape.

My own experience among the Finns, where I did not falter or blanch even though I thought we might have to swim in the ice, is very instructive.

The gale blew in the door. Yes.I held onto Betty Fulbright. I kept my strength up, eating moderately and often. I went down the steps in better shape that I came up. Believe me, it can be done, and I share a faith with Toto:

We are in december's darkest catacombs. The sun is dwindling out. Never mind, old friend. Our feet shall stand our feet shall yell stand, in the temples of July.