Prior to 1929 many observations had been published giving brief accounts of the volcanic ash deposits in various parts of the North Island but no detailed investigations were undertaken. With the incidence of Bush Sickness in the Central North Island mapping of the "ash soils" was undertaken as part of the investigations into the cause of this disease. The work done at this time was the beginning of our present understanding of ash stratigraphy. In this bibliography only papers relevant to the Central North Island ash-showers have been mentioned.