TRENTON, April 27---The will of Stephen Weart Blackwell, who perished on the Titanic, was filed for probate yesterday. No inventory of the estate was given. Harry and William Blackwell, brothers, and Jonathan H. Blackwell, father, are the executors. A memorial service for Mr. Blackwell will be held this afternoon in St. Michael’s Church. A similar service for Washington A. Roebling, second, who also perished on the Titanic, will be held tomorrow in Trinity Episcopal Church.