Lightning Creek occupies a wide valley in a weakened zone in the series of rocks known as the Cariboo schists. It has been stated by Mr. Bowman (Canadian Geological Survey, 1885 and 1886), and confirmed by later observations, that the centre of the deepest known erosion follows very closely the anticlinal axis in these schists. The occurrence of the very rich spots for which this stream is justly famous, both below its present level and at points many feet above it, have long been a source of discussion amongst the miners who worked here. It is hoped these notes gathered during three years studying this difficult problem may be of assistance to future observers, and perhaps lead to the discovery of rich benches in hitherto unsuspected places.