The discovery of the cause of "legion fever" came too late to resurrect this city's most elegant hotel, the Bellevue-Stratford, the hotel's owners said today.

After the mysterious deaths last summer of 29 persons who attended an American Legion convention with headquarters at the Bellevue, the public came to belive that, somehow, the hotel was to blame.

The Bellevue's occupancy rates plummetted and groups canceled their meetings there. The owners acknowledged that the hotel's only salvation lay in a quick discovery by scientists that the disease was caused by forces unconnected with the Bellevue.

When that did not happen by November, the hotel was shut down. Then, on Tuesday, scientists at the U.S. Center for Disease Control in Atlanta announced that a still unnamed bacteria had caused the fatal ailment.

"It's too late now," lamented William Chadwick, the hotel's former general manager. "The hotel was closed and it's on the market."

George H. Johnson, head of the realty firm that is trying to sell the Bellevue, said he expected to meet a Feb. 12 deadline set for accepting the best offer. Johnson said he had been asking $15 million but now "we will look real hard at something approaching $10 million."

Leaders of the American Legion in Pennsylvania said they were delighted by the announcement from Atlanta because, in the words of state adjutant Edward T. Hoak, "This is important to the whole country."

"At least now they're not talking about a toxin ventilation or air conditioning. At least they've pinpointed it down to a specific thing." Now, Hoak said, he hopes the scientific detectives can find out where the organism came from, how it spread and why it struck the persons who became ill or died.

And the legion leaders said they hope, too, that the disease will go down in history by some other name.