“It is impossible to examine this locality without being strongly impressed with the belief that the position which the strata here assume could not have been effected in any other way than by a power operating from beneath upwards and at the same time possessing a progressive force; something analogous to what takes place in the breaking up of the ice of large rivers. The continued swelling of the stream first overcomes the resistance of its frozen surface and having elevated it to a certain extent, it is forced into a vertical position, or thrown over upon the unbroken stratum behind, by the progressive power of the current.” So far as the present writer is aware this is the first recognition in geological literature of the evidence of a horizontally compressive and overturning force as a cause of folding. To E. Hitchcock belongs the credit of being the first to describe overturning and inversion of strata on a large scale, but without clearly recognizing it as such. In western Massachusetts metamorphism is extreme in the lower Paleozoic rocks in the vicinity of the overthrust mass of Archean granite-gneiss which constitutes the Hoosic range. The Paleozoic rocks of the valley to the west are overturned and appear to dip beneath the older rocks. Farther west the metamorphism fades out and the series assumes a normal position. Such an inverted relation, up to that time unknown, is described in 1833 as follows by Hitchcock in his Geology of Massachusetts (pp. 297, 298): “But a singular anomaly in the superposition of the series of rocks above described, presents a great difficulty in this case. The strata of these rocks almost uniformly dip to the east: that is, the newer rocks seem to crop out beneath the older ones; so that the saccharine limestone, associated with gneiss in the eastern part of the range, seems to occupy the uppermost place in the series. Now as superposition is of more value in determining the relative ages of rocks than their mineral characters, must we not conclude that the rocks, as we go westerly from Hoosac mountain, do in fact belong to older groups? The petrifactions which some of them contain, and their decidedly fragmentary character, will not allow such a supposition to be indulged for a moment. It is impossible for a geologist to mistake the evidence, which he sees at almost every step, that he is passing from older to newer formations, just as soon as he begins to cross the valley of Berkshire towards the west. We are driven then to the alternative of supposing, either that there must be a deception in the apparent outcrop of the newer rocks from beneath the older, or that the whole series of strata has been actually thrown over, so as to bring the newest rocks at the bottom. The latter supposition is so improbable that I cannot at present admit it.”