230 Pumpelly and Van Hise — Observations upon 



line of contact between the basal complex and the true con- 

 glomerate, the pseudo-conglomerate also occurs, the fragments 

 being all of one kind, that is derived from the schists intruded. 



Above the line of erosion-contact, within an area of a square 

 yard, in the true conglomerate may be seen fragments of the 

 various rocks which occur in the basal complex ; granites, 

 gneisses and schists of various sorts, all of them showing the 

 characteristic appearance of water rounding. 



Upon the second island the relations are somewhat different 

 from those just described. Here, in passing from the 

 undoubted conglomerate on one side to the granite on the 

 other, is an apparent transition. As the line of contact is 

 neared, the bowlders of the conglomerate which are at first of 

 many varieties gradually become more and more predomi- 

 nantly of the kind of granite which is immediately subjacent. 

 Upon getting closer to the contact these bowlders are found 

 to be angular and finally to have moved but little from their 

 original positions. Finally a transition zone between the 

 conglomerate and the granite-gneiss differs only from the solid 

 mass of the latter in being cut by cracks into which detritus 

 has sifted, and then these gradually die out and we are upon 

 the solid granite. The change from unmistakable conglom- 

 erate to the solid granite takes place in about six feet. The 

 facts here are in perfect accordance with those heretofore de- 

 scribed, only there is the difference that the forces of erosion 

 were not powerful enough to sweep all the coarse debris sharp 

 and clean away from the shore line at this point, but at the 

 beginning of the deposition of the conglomerate, left the 

 blocks of granite and the perhaps somewhat altered granite 

 practically undisturbed. As the sedimentary deposit increased 

 in thickness, more and more material came in from the out- 

 side until the conglomerate took on the ordinary phase. 



This contact east of Thessalon is of unusual importance 

 because of two things : First, it is the only locality known to 

 the writers where may be seen together the intrusive relations 

 so well described by Lawson between granite-gneisses and dark 

 colored schists producing pseudo-conglomerates and imme- 

 diately adjacent to this complex a phenomenon of a wholly dif- 

 ferent order, a true basal conglomerate which marks the 

 beginning of a new series. Second, this locality is important 

 because the contact is between the lowest member of the 

 original Huronian as described by Logan and Murray and their 

 Laurentian of the .North Shore of Lake Huron. Before 

 reaching Thessalon, in going from west to east along the coast, 

 we pass Logan and Murray's lower slate-conglomerate and 

 below this their white quartzite. After passing Thessalon 



