“The fact of W. S. Ayres having at two places within the Gorge series reached the actual bed of the subterranean stream would point to there being no further passages below that level. It would, therefore, appear that the largest accessible portion of the series is now on record. Much of the part shown in red on the accompanying map is difficult of access and dangerous to unskilled climbers. Indeed, for that matter, there are plenty of difficult places throughout.” Formation of the Caves. Mr. Ayres thinks that the Caves have been formed entirely by water erosion, but Mr. Wheeler differs from him in this respect. Mr. Ayres says:— “The rocks in which the Cave occurs are of very hard crystalline limestone, dipping about 30 degrees to the east. In ‘Entrance No. 1’ these beds are very thick and are made up of alternate bands of white, mottled and grey marble. Some of the bands are very highly impregnated with fine sharp sand, so much so, in fact, that excellent whetstones can be made from them. [Illustration: On the road 3½ miles from Glacier. White Pine may be observed along the route—a very unusual spectacle in the Selkirk range of mountains.] “The Cave has, undoubtedly, been formed entirely by water erosion. The stream which formed it, Cougar creek, is entirely made up of glacier and snow water, and above the cave is free from any lime salts. Its capacity, therefore, to dissolve lime rock when brought in contact with it, is at its maximum. The fine grains of sharp sand, loosened from the lime rock and caught in the swift current of the small stream that at first found its way through a shrinkage crack of some particular bed of limestone, have undoubtedly given the water an uncommon erosive power, which, through the countless years of the cave’s history, has enabled that mountain torrent to carve out a mammoth channel in solid marble. “The absence of all stalactites and stalagmites, such as are usually found in caves, and the presence of curiously carved marble walls, wonderfully carved in fantastic shapes and sombre colouring, suddenly make one realize that he is far removed from things familiar.” The Indian word “Nakimu,” by which the Caves are generally known, has the Anglo-Saxon equivalent of “grumbling.” This might imply that in some distant past a seismic disturbance in the interior of the mountain resulted in its Indian appellation, or, on the other hand, it may be due solely to the rumbling sound of the subterranean torrent. Mr. Wheeler, in differing from Mr. Ayres as to the factors mainly instrumental in forming the underground channels and caverns as seen to-day, states his conviction that an agency, more potent and far-reaching than mere erosion and disintegration by the ordinary processes of nature, has been at work. In his arguments in this connection he says:—