Dr. W. T. Grenfell, the founder of the Poor Relief Stations of Labrador, will speak at St. Paul's Cathedral, Tremont street, Boston, tonight at 8 o'clock. His subject is to be "The Greatest Prize in the World," the lecture being open to the public. Owing to the necessary cancellation of Dr. Grenfell's address at the Union, this opportunity to hear him in Boston should be welcome to Harvard men.