Arthur S. Biddle '48 of Claverly Hall, a 20-year-old College Junior from Chicago, emerged last night as the chief figure in a water rescue of three persons whose automobile had plunged through a bridge railing into the Fort Point Channel in back of South Station.

Police reported that at 10 o'clock an auto collided with a U. S. mail truck parked outside the Post Office Annex, and that the smash-up drove the smaller vehicle off the bridge. Biddle, a chance passer-by, quickly dove in after the disappearing car.

Joined by three postal employees, he succeeded in the rescue of two women, Miss Joy Moffett, 24, and Miss Jean Williams, the same age, both of Medford.

Man Also Saved

Quick thinking by Biddle and the clerks also saved Alfred Swenson, 23, of North Quincy. Kaevin Gennehey, 26, of Quincy, believed to be the driver, was pinned beneath the wreckage of the car on the bottom of the canal, and repeated diving was unsuccessful in reaching the body.

Biddle was rushed to Boston City Hospital for exposure treatment, where his condition was reported "good" later last night. His two roommates noted that he left his second floor Claverly room at 8:30 o'clock, but neither could advance any reason for his presence on the Fort Point Bridge.

He is a biology major and during the war was a radio technician in the Navy.