sa 
in St. Lawrence Co., N. ¥. 25 
There is no doubt but that his fis views regarding the 
rigin of limestones stood somewhat in the way of his seeing 
all the facts that this interesting dumtiew exhibits. His section 
of the Parish ore bed, page 93, ote Iv, does not represent the 
facts now to be observed. I found on magnesian schist 
where he has marked gneiss. It should be remarked, however, 
that there has been a large amount of work done of late years, 
revealing many additional facts. 
r. Emmons gives 60 to 300 feet as the minimum and maxi- 
mum thicknesses of the Potsdam sandstone in northern New 
York, and it has been described as diminishing in some in- 
stances to 20 or 80 feet. The prevailing rock observed in this 
region seems to have been a Latinas d sandstone, frequently 
having a conglomerate as its lower member. Nor have any 
rocks of different lithological character been ascribed to this 
ab in the region in question; although partly calcareous 
ers and even beds of true limestone have been observed in 
the upper rocks of this period in the northwest. The rocks I 
have described, therefore, have apparently too great a thickness — 
and show too wide a variation in lithological.character to be 
regarded as the equivalents of the Potsdam. Some forms, 
obtained from a calcareous layer the base of the upper sand- 
stone, which I thought might be organic, were pronounced 
by Dr. Newberry to be concretions. The ee ig of graphite 
was the only evidence of organic life obser 
The Potsdam quarries are only 35 wiles ‘northeasterly from 
the Rossie mines, and the country between was examine y 
mmons. He may have traced the sandstone throug 
stratigraphically. My own reconnaissance of this country leads 
me to believe that this could easily be accomplished. Should 
it be done, a point of considerable interest which would be 
incidentally settled is this:—Does the Potsdam sandstone in 
this 2yov eaycae his places, decidedly gneissic in character? 
y own hasty observations at the Sterling and Tate ore beds 
leads me to believe that it ‘does: if so, the Tate bed de- 
scribed by Dr. Emmons, pages 95 and 846, as being overlaid by 
gneiss, may be found to be the equivalent of the Rossie beds, 
which I believe to be “the ease. ‘The ores are certainly very 
similar. This Tate bed confirmed Dr. aA and with go 
reason, in his view, that the iron ores were of “primitive age,” 
lying either in or immediately on top of the great gneissic 
seri 
AE bearing on this subject, I would mention that the iron 
ores of the Siirernee: district in Crawford and Phelps Co., 
o., bear a close resemblance to those of Rossie, and work 
equall well in the furnace. The Missouri ore contains con- 
siderable yellow ochre, which is less abundant at Rossie; but 
