By the invitation of the Mica Corporation of Australia Limited, and the generous assistance of a number of donors, I was enabled to accompany Messrs. J. Dale and R. Barlow on an expedition to Central Australia. Our method of transport was by motor lorry, and altogether we travelled 850 miles in Central Australia. Entering the Territory from Queensland at about latitude 21°51′ south, we travelled 25 miles south along the Queensland-Central Australia border fence to Tobermory Station, and then in a general west-by-south direction for 204 miles to Oorabbra Water Holes. From here we changed direction to approximately south-west. Crossing the Marshall and Plenty Rivers, and passing over the Hart Range, through Arltunga, we reached Alice Springs in the MacDonnell Range, a further distance of 180 miles. Returning to the Hart Range, we established a camp and remained in these ranges for a period of four weeks. It will be obvious that any work carried out is purely in the nature of reconnaissance, and all that can be hoped for is that these notes may add a little to our knowledge of this very remote and exceedingly interesting area. I am greatly indebted to Assistant Professor W. R. Browne for much valuable help in their preparation and for petrological determinations, and to Mr. R. O. Chalmers for the chemical analyses carried out by him.