Counter Studies on Cosmic Rays at Sea Level

Part I: Rossi transition curves for lead up to 400 g/${\mathrm{cm}}^2$ were studied with a triple coincidence counter arrangement in various geometrical configurations with shower angles from 4° to 60°; variations of cosmic-ray intensities were recorded simultaneously with a twofold vertical coincidence set and every point of the transition curves corrected accordingly. Even with small angle showers in an arrangement practically identical with Bothe and Schmeiser's no second maximum of the Rossi curve could be found. Absorption of shower particles and back scattering were studied.