Structure of Air Showers

Cosmic-ray air showers of total energy in the range ${10}^{14}$ to ${10}^{15}$ ev have been studied at 3260-m elevation with a large multiplate cloud chamber in combination with five thin-walled ionization chambers. The spatial distribution of electrons near the shower axis is usually a smooth function of distance with a singularity less marked than $\frac{1}{r}$. Evidence is presented, however, to show that some showers have a lumpy structure near the axis. The showers are very poor in high-energy electrons and photons near the axis, relative to the expectation for a single electron-photon cascade. The angular distributions of shower axes are found for various shower sizes and prove to be quite similar to those expected for single electron-photon cascades. The implications for various shower models are discussed and a fairly extensive nucleonic cascade is indicated.