184 Proceedings, 



typical Huronian but more recent than the Laurentian. It then gave the re- 

 sults of some observations at North Bay, Wahnapitae, the copper mines 9j; 

 Sudbury, Algoma and Serpent river, and the inferences arrived at are to the 

 effect that two formations have been confounded under one name (Hurop- 

 ian) as follows: 



[Summary of these Observations.^ 



It appears, therefore, that both northwest from Sudbury and eastward 

 from Algoma there are two formations. The slate and the slate conglomer- 

 ate in both sections constitute the upper formation. In the region north- 

 west from Sudbury the underlying rocks are largely felsitic, but are also 

 micaceous, and of the Stobie mines become hornblendic. These changes 

 are identical with changes that are known to occur in the Keewatin in Min- 

 nesota. In the section eastward from Algoma the underlying formation 

 seems to be the Missasaugui quartzite with interbeding of green fissile 

 schist, in part, and a mica schist, varying to hornblendic schist, in part, the 

 latter being the furthest east. 



There seems to be some irregularity in the order of succession in the 

 section eastward from Algoma, bringing in several outcrops of strata that be- 

 long higher up in the series. If this be not illusory, and due rather to the 

 winding of the railroad from north to south to avoid the hills, it may be ac- 

 counted for by such faulting and upheaval as have been described in Min- 

 nesota, such as have produced the sudden, but indistinct, unconformities^ 

 and transitions from the Huronian to the Keewatin, that have been de- 

 scribed there. Further, the quartzite which has been alluded to as the 

 Missasaugui quartzite, and supposed to be Logan's lowest gray quartzite,. 

 is probably not his lowest gray quartzite, but it is a rather a constituent part 

 of the Keewatin. It is allied in all its lithology no less than its persistent 

 verticality, to the Keewatin, and seems to have been formed in the Keew^atin 

 ocean in the same manner as the jaspilite beds of that horizon — i. e. by , 

 chemical precipitation, the green schist layers showing such advent of basic 

 eruptions or volcanic ash as could form chloritic schists, in the same way as 

 in northeastern Minnesota. The "lower gray quartzite," (No. 5a) of the orig- 

 nal Huronian, according to Logan's map of 1863, appears a few miles east 

 of Thessalon at the lake shore, and there produces an unconformable con- 

 tact on the gneiss of the Laurentian. This contact has been examined by 

 Prof. Irving and more lately by Dr. A. C. Lawson, and they concur in the 

 statement that the conglomerate is a pudding-stone of rounded masses, hav- 

 ing a quartzite matrix. There can be but little doubt that it is the same 

 seen in the vicinity of Thessalon, and hence that is the Thessalon quartzite,. 

 and overlies the slates and slate conglomerates, being near the top rather 

 than near the bottom of the original Huronian. This mistake is apparently 

 the same as that made in eastern NewYork and inVermont, where the granu- 

 lar quartz and the Potsdam (or red sandrock) seem to overlap and hide from 

 sight the formation immediately older, and lie in unconformity on a still 

 older terrane— on the east on the gneiss of the Green mountains, and on the 

 west on the gneiss of the Adirondacks. It caused the early geologists to 

 question the existence of any such formation as the Taconic — that grea.t 



