Geology of Lake Superior. 27 
into sandstone. That Gentleman thinks that these trap veins 
traverse all the rock formations of the lake promiscuously. 
There certainly appears an intimate connexion between 
the various orders of rocks which we have mentioned. We 
think the immense beds of greenstone which are superimpo- 
sed upon the sandstone in Neepigon Bay, an instance of this- 
As for the latter rock resting upon and alternating with amyg- 
daloid, it does so only in one or two instances, and to small 
extent, and may possibly arise from displacement. 
We have already recorded our opinion as to the porphyry 
passing into sandstone ; and we are equally incredulous as to 
amygdaloid passing into granite. Facts so contrary to the re- 
sults of former experience and observation, must be clearly 
and obviously esjablished, before they can meet with general 
reception. 
It has been written that the sandstone is contemporaneou, 
with the amygdaloids and porphyries ; and younger, but not 
much more so, than the granite. The following considerations 
may possibly throw some light upon this subject. It is ackhnow- 
ledged that the nodules of the coarser kinds of this sandstone 
are often composed of the trap rocks* as well as of the in- 
ferior order. In short there is scarcely a rock in the Jake, of 
which rounded masses may not be found in this formation, 
Hence it is obvious that those rocks, not only were formed 
first ; but that they have, subsequently to their formation, been 
shattered by some powerful agent. The fragments are all 
worn perfectly smooth, and most of them have been complete- 
ly rounded by attrition. It seems therefore equally probable 
that they have been subjected to the long continued action of 
powerful streams of water, before they were deposited in their 
present horizontal strata. 
How 
We have seen this conglomerate, in some places almost entirely 
composed of porphyries and other trap rocks; not only its nodules 
but also its cement, 
