Full Idea
In 1918 Russell does not admit facts as fundamental; atomic facts are atomic as facts go, but they are compound objects. The atoms of Russell's logical atomism are not atomic facts but sense data.
Gist of Idea
Russell's atomic facts are actually compounds, and his true logical atoms are sense data
Source
report of Bertrand Russell (The Philosophy of Logical Atomism [1918]) by Willard Quine - Russell's Ontological Development p.83
Book Reference
Quine,Willard: 'Theories and Things' [Harvard 1981], p.83
A Reaction
By about 1921 Russell had totally given up sense-data, because he had been reading behaviourist psychology.