A fire official kept time in Huntington Station Friday evening as 1,500 firefighters filed in rigid groups of eight past the widow of Rescue Co. 4 firefighter Peter Nelson and a floral Maltese cross during a memorial service at his firehouse. But Gigi Nelson's mind was on another clock.

She was timing contractions.

Three hours after that service and 25 days after her husband was lost in the collapse of the World Trade Center, Gigi Nelson gave birth to 6-pound, 1-ounce Lyndsi Ann. She then left the hospital for an hour Saturday morning, in a Huntington Community Ambulance, to attend a church service on his behalf before returning to the hospital to care for their first child.

Peter Nelson, 42, a 15-year firefighter with the city, was a third assistant chief at Huntington Manor, where he had been a volunteer from age 18, and much loved as a fearless firefighter and skilled teacher.

In the city, Nelson had spent most of his career in the pleasant Tudor-style quarters of Ladder Co. 151 in Forest Hills, when he was selected for the faster- pace elite Queens rescue company in July. He was working overtime on Sept. 11 to help save for his new baby.

The last time that Huntington Manor Chief Charles Hoffman saw Nelson was the night of Sept. 10. Nelson had attended a Lamaze class with his wife before going to a department meeting.

"We all made fun of him, panting," recalled Hoffman, imitating the huff-puff breathing Lamaze students are taught to ease labor. "He was one of the best of the best."

Gigi Nelson spent her final weeks of pregnancy in a vigil by the phone, with a never-ending stream of firefighters and neighbors sharing the wait with her.

Huntington Manor firefighters sent over twice-a-day meals for up to 50 people, along with sodas and ice. Childhood friends came by to tell stories from Nelson's younger days, when he earned the nickname "Petley" because he was charming enough to "peddle" anything to anyone. Over and over, she said, friends described Nelson as a man who always put other people first.

"You're scared," she admitted yesterday, just home from the hospital with her newborn, as usual to a houseful of helpful people. "You think you're going to have the father there. I miss him.

"But I also know that I'm compiling a scrapbook for his daughter," she said. "I can safely tell her that her father is a hero and he gave his life to save others. That's a comfort. And I have her. She's kept me going. This is a lifeline to Pete, and I'll always have that."

In addition to his wife and new daughter, Nelson is survived by two children from a previous marriage, Jamie and Ryan Nelson of Huntington Station; his parents, Alfred and Joan Nelson of North Carolina; and two brothers, Alfred Nelson Jr. of North Carolina and John Nelson of Northport.