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otherwise occupied the channel previously cut, and that the stream gradually built up its gravels within the tunnel so formed, essentially as indicated by Professor Russell in the case of tunnels under the Malaspina glacier. While the inferences drawn from this peculiar association of the osar ridges with river-like channels cannot be urged with the same force as the preceding considerations, they seem to support them in some degree. The constitution of these osar ridges is of the same local character as that of the kames above discussed except that perhaps it is less narrowly local and less intimately related to the underlying formations. The difference, however, is not marked.

From the foregoing evidences, the inference is drawn that the osars and kames of the plain region of the interior are basal phenomena in a degree almost as complete as the drumlins or the ground moraine. Inferences from such evidences as have been cited cannot, however, be applied with so much rigor in the case of osars and kames as in the case of drumlins, for the subglacial streams, that are held to have formed them, cannot be assumed to have always pursued strictly basal courses. Conditions may be supposed to have arisen which would have forced the streams into channels above the base of the ice, or even up over the ice in the thin marginal portion, so that accumulations may have taken place that were less strictly basal than those of the drumlins, and it is of course possible that kames and osars may have been formed, in particular instances, out of the englacial and superglacial material of the ice; but, following what seems to me the legitimate teachings of the foregoing lines of evidence and of observation, there seems warrant for concluding that such instances, though theoretically possible, are practically rare. I beg that it may be observed that these conclusions are drawn from the phenomena of the plain region of the interior and are applied to it, with the full recognition of the possibility that in hilly and mountainous regions modifications of the conclusions may be necessary.