Then at a Trustees meeting the following May, "Mrs. Whitin stated that she now proposes to construct the Observatory of white marble in place of brick."

When it was formally opened on October 8, 1900, Miss Hazard could report that it housed "a 12" refractor with micrometer, polarizing photometer, and star and sun spectroscopes.

A Rowland concave grating spectroscope, of 6' focus, with its accompanying heliostat, is set up in a room capable of being darkened completely.

The library is a beautiful room, and the dome by Warner and Swasey is all that it should be.Whiting used the telescope in teaching her classes in astronomy to Wellesley students, one of the first of its kind.

Various compromise building materials for the addition were discussed, but after many consultations with the architect, she declared that "marble and copper were good enough," and by 1906 the observatory was doubled with increased equipment, and a house placed beside it, completing a harmonious group, and itself a lovely specimen of domestic architecture.According to Wellesley records, in 1942, before the U.S. entered World War II, "astronomy professor Helen Dodson and Barbara McCarthy, professor of Greek, teach a secret course in cryptography to (at least) ten students.