By the way, a week later we're still trying to figure out what this was all about, and we note with trepidation that there have been no follow-up stories. WW4 Report's chief blogger became aware of the smell at around 7.30 PM Oct. 28 on Whitehall Street in the Financial District. It was still evident, although fainter, upon arriving by bicycle in the Lower East Side, some two miles uptown. The immediate association for this observer was butterscotch. Is it just us, or does anyone else think it might have been a clandestine test of a dispersal agent to simulate bio-chemical attack, such as have been held (overtly) in the city in recent weeks? Or, ominously, an actual attack with some kind of slow-acting bio-chem agent? From the NY Times, Oct. 29:

Good Smell Vanishes, But It Leaves Air of Mystery
The night air all over Manhattan was brisk, with a hint of winter and a dash of something sweetly out of the ordinary. Some thought it smelled like maple syrup. Some said caramel, or a freshly baked pie, or Bit-O-Honey candy bars.

From downtown Manhattan to the Upper East Side, Prospect Heights in Brooklyn and parts of Staten Island, the question was the same on Thursday night and into early yesterday: What was that smell?

The aroma not only revived memories of childhood, but in a city scared by terrorism, it raised vague worries about an attack deviously cloaked in the smell of grandma's kitchen.

It was so seductive that many New Yorkers found themselves behaving strangely, succumbing to urges usually kept under wraps. One woman who never touches the stuff said she was inspired to eat ice cream.

Late yesterday, nearly 24 hours after the smell had spread through the city, sparking hundreds of bewildered calls to the city's 311 emergency hot line, officials said that they had determined that the smell had not been hazardous and that it had dissipated as quickly, and mysteriously, as it had appeared.

Even after chasing down anonymous tips and chasing up several blind alleys, however, they did not know where it had come from.

The odor was first detected around 8 p.m. on Thursday in Lower Manhattan. It seemed to spread quickly uptown and into parts of the other boroughs - so quickly that officials expressed concern. The city's Office of Emergency Management sent out feelers to the Police and Fire Departments, state emergency response agencies in New York and New Jersey, and the United States Coast Guard, which communicated with tugboats and container ships at sea to determine whether the odor was being detected there.

Raymond W. Kelly, the New York City police commissioner, coolly told reporters yesterday that tests and air monitoring had revealed "nothing of a hazardous nature."

"It's believed to be some sort of food substance, but we can't substantiate that at this time," Mr. Kelly said. He confirmed that the source of the smell seemed to be in Lower Manhattan.

The chase led the city's environmental bloodhounds to some interesting places. Investigators working on a tip checked the Jacques Torres Chocolate Haven in SoHo, but the owner insisted he had not been the culprit. His staff had spent the afternoon roasting almonds, he said. And anyway, chocolate, for those who really know, smells bitter, not sweet.

"Perhaps if it was a chocolate smell, people would be running here today," Mr. Torres said from his shop, which he said was no busier than normal for a Friday in autumn. His chef, Susana Garcia, 31, who was on duty Thursday, said the mysterious odor was definitely more like maple syrup than like chocolate. It was, Mr. Torres said, a kind of warm-your-heart holiday smell appropriate for this time of year.

If there was anyone in New York who could recognize the aroma of maple syrup, it would be a Canadian like Jeff Breithaupt, 42, cultural affairs officer at the Canadian Consulate in New York. He said he was out running on the Upper East Side last night when the smell came to him. Right away, he thought it was caramel candy.

A labor organizer, Rekha Eanni, said she could not characterize the exact smell, but after getting out of a night class at New York University she was overcome with a craving for pumpkin pie. When she got home there was no pie, so she did something she never does.

"I made myself a pretty big bowl of vanilla ice cream with honey and cornflakes," she said.

Experts say that no human sense is more directly connected to the emotions than the sense of smell. "Before we know we are even in contact with a smell we have already received it and reacted to it," a professional perfumer, Mandy Aftel, said. "Smells come in without language and go directly to the emotional center of the brain. That's why they are so connected to memory."

As soon as he smelled the mystery smell, Greg Nickson, 45, a freelance cameraman, was transported, like Marcel Proust, to things past, things like the chocolate factory that flooded his childhood neighborhood in Chicago with sweet aromas.

When he poked his head out of his 10th-floor apartment window to look for his wife, Mr. Nickson got a good whiff of it, and it puzzled him.

"I thought," he said. " 'How could the smell be so pervasive?' "

With the cold nighttime air trapped under a lid of warm air over the city, and only a 3-mile-an-hour wind, any odor would have been kept low to the ground, where it could have slipped between buildings to work its way uptown and to the other boroughs, said Patrick Kinney, an associate professor of environmental science at Columbia University.

When Mayor Michael R. Bloomberg was asked at City Hall about the smell, he repeated that tests showed it was not dangerous.

With the mayor enjoying a sizable lead in polls about the upcoming election, someone asked whether it struck him as, perhaps, the sweet smell of success.

He gave an enigmatic answer. "Nature," the mayor said, "should be allowed to take care of its own."