A discussion of the development of the Geiger counter as applied to cosmic rays is given. The development of coincidence selecting circuits is particularly emphasised and various types of circuits are described in detail.
Experiments dealing with the coincidences observed between three counters separated by considerable thicknesses of lead are shown to offer evidence that such coincidences are for the most part caused by the passage of single particles in straight lines through the counters and the intervening lead. Perhaps 10% of the coincidences arise from secondary particles operating at least one of the counters.
Several types of shower experiment are described and an analysis of the curves obtained is made. This leads to an estimate of the rates of absorption of the shower producing radiation and the shower particles. Further experiments give information as to the nature of this radiation and of the showers themselves.
Experiments on the variation of the showers with altitude and latitude are also described. These show that although the showers are softer than the general radiation they suffer a smaller latitude effect.
