With the agreement of President Haskins, Tuve selected Ellis Bolton to follow him as Director and to this end named him Associate Director in July 1964. Bolton, known for his contribution to the agar column, a crucial preliminary to the discovery of repeated DNA sequences, felt insecure in dealing with so many physicists and recommended Aldrich to be his associate; he was named Assistant Director the following year. Thus arrangements were made for a smooth transition. When Tuve stepped down on 30 June 1966 he left the most diverse department of the Institution. In numbers of staff and staff associates the bio group had five, seismology four, isotope geology two, radio astronomy two, image tubes and optical astronomy two, cosmic rays one, and nuclear physics one. Administratively it lacked cohesion.

Seismology, isotopes and cosmic rays fitted well with the new directions selected in 1946 for expansion in the study of the Earth using the methods of physics. They were productive of ideas and results, and of the 14 Fellows listed in Bolton's first year, 10 were in this group.

Radio astronomy had come into being to explore remarkable postwar discoveries, a task that had been well handled, but it now had only Turner (staff associate) and Tuve (emeritus), others having left the Department during the preceding few years. A large investment had been made in an 18 m steerable dish, the operation and maintenance of which was substantial.