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usually tilted at high angles. There are numerous instances where there is a gradual transition from the Huronian to the lower series. A few instances of local want of conformity between the two is no evidence that the two systems are not conformable on a grand scale. The few known instances where there appears to be a want of parallelism are more probably due to faulting. The pyroclastic rocks show the agency of water in their formation, and were largely derived from igneous matter, which had been more or less recently erupted. The newest rock of the Sudbury district is a volcanic breccia, which forms a continuous range of hills for a distance of thirty-six miles, with a breadth in the center of eight miles. Within the Huronian rocks are intrusive red granites.

Comments. Attention is called to the implication that the unconformity at the base of the Huronian, if it exist at all, is of a local character. The very idea of an unconformity pre-supposes that it can not be local in the narrow sense. A minor unconformity even marks a considerable time break, and when an earlier series has been profoundly metamorphosed and deeply denuded before the overlying series is deposited upon it, the break must be of regional extent, even if the contacts found are few and of small extent. It, however, does not follow that the break is universal not even that it always extends throughout a geological basin. Space does not permit a discussion of the evidence for the existence of unconformable contacts at the base of the original Huronian in certain localities. It is enough to say that Irving, Pumpelly, Reusch, Barrois, and Tschernychew, all having seen one of the localities and the first two both, agree that the only interpretation of the phenomena at points near Garden river and near Thessalon is that of a great unconformity, not faulting as suggested by Bell, who does not appear to have ever visited these localities.

Barlow^[1] states that the Huronian system is the oldest sedimentary strata of the north shore of Lake Huron, and that the Laurentian gneiss or Basement Complex is the original crust of the earth or floor on which the sediments were laid down. This floor, as shown by the pebbles of the Huronian, was granite which had in many places a foliated or gneissic structure. In many places the subsequent folding and fracturing of the comparatively thin crust of the earth has caused large portions of the Huronian to sink below the plane of fusion, the result of which has been to produce irruptive contacts. At other places, as described by Pumpelly and Van Hise, the Basement Complex may have remained undisturbed so that the overlying detritals have not been intruded by the granitic mass beneath.

Hall and Sardeson^[2] describe the Upper Cambrian rocks of Southeastern