Contents: 5 • Microclock • [Editorial (Astounding)] • essay by John W. Campbell, Jr. [as by The Editor] 7 • World of Null-A (Part 2 of 3) • [Null-A • 1] • serial by A. E. van Vogt (book publication as The World of Null-A 1948) 47 • Uncommon Sense • [Laird Cunningham] • short story by Hal Clement 63 • The Infidels • short story by Ross Rocklynne 83 • The Power • short story by Murray Leinster 99 • Tool • essay by uncredited 101 • The Elusive Microvolt • essay by George O. Smith 115 • Deadly Host • short story by Raymond F. Jones 135 • Camouflage • novelette by Henry Kuttner and C. L. Moore [as by Lewis Padgett] 165 • In Times to Come (Astounding, September 1945) • [In Times to Come (Astounding)] • essay by The Editor.