Usually, life is a smooth sail for Sir Francis. After all, when you're a drake, and you live in a pentagonal pool that the government maintains in front of the Interior Department, you get lots of cooing from tourists and bites of bologna from bureaucrats.

Sir Francis has spent the last nine years lapping up attention and calories near the corner of 19th and C streets NW, with only occasional time off to father a few ducklings. Longtime observers can't every recall him being nervous.

Until last week. And he wasn't alone.

Three edgy technical specialists from the National Park Service came to the lip of Sir Francis' pool. Their immediate concern was not him, but a buildup of algae in the pool -- great globs of green goop that looked like undercooked spinach. Unless the men could prevent the goop from multiplying in rabbit-like proportions, Francis and all eight of his mates and children might have to leave.

John Hoke was the chief government worrywart on the scene. There couldn't be a more colorful one.

Hoke arrived in an electric cart (he disdains internal combustion engines). He wore a pit helmet fitted with a solar-powered blower ("air conditions my scalp," he explained). And he brought along a theory about why the algae had suddenly begun to multiply so rapidly.

"You first have to understand that theories is all we have," said Hoke. "We don't know how the algae got here, and we aren't sure why it does so well in an environment like this, where the water hasn't been changed in five years.

"My own guess is that all the hot days we've been having somehow broke down a barrier to reproduction that's normally there."

It would take a week -- and $5,000 -- to remove the algae from the pool by draining it, Hoke estimated. "So we're trying to get natural mechanisms to control it," Hoke said.

For instance?

"You remember your paramecia, from high school? Them, for openers. And other little bugs. They have to eat. We hope they'll eat the algae."

But no such luck. By last Friday, the algae had multiplied to the point where the pool started looking like an ad for Astroturf.

Just as serious, Sir Francis and his relatives, who had first come to 19th and C on their own, were beginning to depart on their own. Witnesses saw them hanging out down by the Reflecting Pool.

So Hoke finally resorted to chemical warfare -- a massive infusion of copper sulfate.

That isn't as desirable a solution as hungry paramecia would have been, for the side effects of copper sulfate are not entirely known. Still, the immediate result was also the desired result: the algae went away, and the ducks all came back. "We're satisfied -- until the next time," Hoke said.

And Sir Francis? He blinked twice at an inquiring reporter the other day. It must have been duck-ese for "Thank Heavens."

Touche to Syd Kasper of Silver Spring, whose relentlessly sharp grammatical eye has picked up a real "baddie" in a house ad that ran in The Post on July 7.

The ad announced the new mechanical specifications that The Post adopted on July 13. "Mechanicals for display advertisements . . . can be prepared in the exact same size (italics mine) as the published ad, the text said.

Why not write it "exact same precise equal identical size?" Syd asks. "Then there could hardly scarcely barely be any mistake error fault misconception or misunderstanding about it."

No sooner did I beat up on TV weathercaster Paul Anthony for an ungrammaticism the other day than Grace Glick of Arlington called.

With another.

It seems Anthony was giving the high and low tides the other day. "They will take place at 8:02 a.m. and 8:47 p.m., respectfully," Grace swears he said.

Speaking of weather, Forest Pinkerton of Alexandria called with a darn good question about the "wind-chill factor."

Why, he asks, don't weatherpersons report it in the summer as well as the winter?

Ninety-five degree days sound awful, Forest points out. Wouldn't 95-with-a-wind-chill-of-75 sound better?