“At one spot the passageway twists in a loop, and here the potholes are of such a curiously spiral form that it has been named ‘The Corkscrew.’ Across this bend, about 12 feet above the main floor, a gallery extends for 120 feet. It is of a similar pothole formation, but on a smaller scale than the main passageway. Directly below it, at the lower end, is a peculiar sharp spike of rock that has evidently been subsequently carved out by water pouring from this gallery, as is readily shown by the erosionmarks on the component rocks. In addition to the lines of erosion on the rock spike and in the gallery pothole, honey-combing is seen on the right and high up on the left and, still farther on the left, spatulated markings to the depth of half an inch, or a little over, which is a very common feature in all three series. “Throughout the Mill Bridge series, with the exception of the Auditorium, the floors and ceilings are of water-worn rock, and practically no debris has fallen away pointing to the fact that this channel is of more recent origin, and the rock through which it has worn of a more compact stratification. “At one time it was reported that the roof of this passage was set with sparkling quartz crystals. It turned out, however, that they were only drops of water that had collected through leakage or condensation. Some of the potholes are very curiously marked by thin incrustations of carbonate of lime spreading over their concave surfaces in florescent patterns. Overhead in many places are seen projecting spurs that have withstood the action of the water owing to superior hardness, or that, through some deflection of the current, have not had the same force brought to bear upon them. The waters of Cougar creek are derived from the melting glaciers and snow deposits lining the sides of the peaks enclosing the valley and, in consequence, carry a considerable quantity of sediment, composed of very fine rock particles. The quantity of sediment carried would, of course, be greatest when the stream was at flood stage. This sediment has doubtless been a factor of much importance in the erosive power of the waters, and a residue may to-day be seen as a very thin mud-coloured coating on the walls and floors of the passageways, where it has been deposited by the subsiding waters. At a very high stage of water in the creek there was an overflow into Entrance No. 1 that made the first exploration by W. S. Ayres and party a wet and somewhat dangerous operation. This overflow, however, was dammed back by Deutschman, and no further trouble has since been experienced with it. The Gorge Series.