Six instrumented rockets were used to probe three separate ion clouds that resulted from F-region barium releases, and measure electron density structure within the clouds. Two probes were launched into each of the three ion clouds, and each probe showed considerable enhancement in F-region electron density over the normal background levels. In four traversals the electron density exceeded 1,000,000/cu.cm. with a maximum of 5,000,000/cu.cm. observed in one case. Two showed dramatic structure in the electron density profiles associated with passage through striated portions of the cloud. These structures had spatial extent as measured by the rocket probes normal to the terrestrial magnetic field of hundreds of meters with the density changing by factors of from about 2 to 10 as the probes passed into and out of the structure. The change of density on some of the features had particularly fast drop off, corresponding to less than 20 meters travel normal to the magnetic field.