“That disturbances of this nature have taken place in Canada at a much more recent date is pointed out in the above report by the following quotation from the ‘_Jesuite Relations_,’ Thwaites translations, vol. xlvii, pp. 37-57; 183-223: ‘On the fifth of February, 1663, towards half-past five in the evening, a loud roaring was heard at the same time throughout the length and breadth of Canadas. . . . On level ground, hills have arisen; mountains, on the other hand, have been depressed and flattened. Chasms of wonderful depth, exhaling a foul stench, have been hollowed out in many places, plains lie open, far and wide, where there were formerly very dense and lofty forests. Cliffs, although not quite levelled with the soil, have been shattered and overturned.’ [Illustration: Government building at the Caves for the use of visitors.] “If the origin of block moraines can be accounted for by seismic disturbances, it is not improbable to assume that at some remote date a similar occurrence has shattered this bed of crystalline limestone and precipitated Cougar creek from its surface course into subterranean channels, which, through the course of ages, it has enlarged to their present size, and that subsequent shocks have been mainly responsible for the large quantities of fallen debris that litter the interiors. Under such a condition of affairs, the crack of the Gorge, and similar chasms found below the surface, would be accounted for.” The gist of Mr. Ayres’ arguments concerning the probable age of the cave is contained in the following paragraphs:— “The marble rocks in which the cave is formed belong most probably to the Devonian age. No fossils were found, however, to positively verify this conclusion. The limestone rocks have not been completely changed into marble at all points as was observed under ‘Gopher Bridge’ and in ‘The Terror.’ Notwithstanding the fact that the rocks belong to a comparatively old series, yet the beginning of the cave undoubtedly dates from a very recent geological time. “Assuming the rate of erosion to be one thirty-second of an inch in a year, then to cut down one hundred feet of rock, which is about the average amount eroded in the main cave, would require 38,400 years. Any actual rate greater or less than this assumption would increase or diminish the age of the cave. In several places along Cougar creek in the bottom of the cave an excellent opportunity is afforded to determine actually the present annual rate of erosion. A micrometer measuring apparatus should be used and the area of cross-section of the rock eroded per year thus accurately computed. Also the ratio between the area of the cross-section of the average stream and the area of the rock eroded should be determined. And finally, the quantity of water passing the given section in one year, and its velocity, should be accurately measured.