Four miles up that valley, a man of thirty was doing a different sum and had been doing it for four years.
"Ninety-one," said Magnus Blackwood.
His uncle said nothing, which is what he did when he had decided a thing was foolish.
"Ninety-one men of fighting age on this ground. I have counted them twice and I have a name for every one and I have them by township on a sheet.
"In the year five my grandfather could put a hundred and forty in a field.
"And I have gone through it four times, uncle, and it is not the plague and it is not the harvests. It is the feud, and I have the years against the names, and there are nineteen of them."
He had the sheet on the table.
That is a thing worth understanding about Magnus Blackwood, and it is why everything happened the way it did: he was the second son. He was to have had the ground at Auchen and a quiet life and had been raised for it, and he had spent four years at Glasgow at the university, which nobody in that valley had done since about 1490 and which four men on his own land thought was a joke.
He came back at twenty-two because his elder brother wanted him back.
And in the year twenty, on the same afternoon, at a place called the Rig, he lost his father and Ruaridh, and was head of that name at six and twenty with a sheet of paper and no idea whatsoever what he was doing.
"There are eleven households at Blacklaw," he said, "with a woman in them and no man. Eleven, uncle. I have been in nine of them.
"There are four boys of fifteen doing a man's work at the sheep because there is nobody else and they will be dead at thirty from it.
"And every time we take one of theirs they take one of ours, and I have written it out, and at this rate there is no Blackwood in this valley by the year sixty."
Fergus Blackwood put his cup down.
"There is another way of counting it," he said.
"Is there."
"Aye. Kerr had a hundred and ten in the year five and he has sixty-four now, and I have counted his as well, and I have been counting his since before you could ride."
He leaned forward.
"You are counting when we die out," said Fergus Blackwood. "I am counting when they do.
"Nine more years of this and Kerrsyde is an old man and a woman in a house, and that whole ground is ours without a paper and without a court and without one merk of assythment to anybody."
Magnus Blackwood looked at his uncle for a long moment.
"And how many of ours in nine years?"
"Whatever it takes."
"That is not a number, uncle."
"It is a price," said Fergus Blackwood, "and men in this valley have paid it since before either of us, and you are the first Blackwood in a hundred years who has sat in that chair and asked to see the bill."