282 R. D. Irving—Age of the Metamorphic Rocks 
which the crude acid had been precipitated was also treated 
with ether. On uniting the ethereal solutions and distilling off 
the ether, a residue was obtained which dissolved readily in 
alkaline carbonates. It was neutralized with barium carbonate. 
The barium salt was easily soluble and crystallized well. The 
free acid separated from this salt was easily soluble in hot water 
and crystallized out on cooling. It had the fusing point 120° and 
all the other properties of benzoic acid. No other substance 
could be found. The quantity of benzoic acid obtained was 
very small in comparison to the whole quantity of the product ; 
and its formation can easily be accounted for when we consider 
the character of the reaction. 
ere then, at least, no molecular rearrangement takes place; 
and this, taken in connection with Meyer’s experiment, certainly 
makes the case strong enough to command attention. The 
reaction is thus shown to be capable of application for the 
purpose of determining the constitution of compounds; and 
the changes proposed by Meyer can be demanded with greater 
confidence than before. The proofs that paraoxybenzoic and 
terephtalic acids belong to the same series had already been 
given* by other reactions; though, acknowledging the de- 
scribed reaction, this would be the most direct proof of the fact. 
(To be continued.) 
Art. XX XI.—WNote on the Age of the Metamorphic Rocks of Port 
land, Dodge county, Wisconsin; by Rouanp D. Irvine, E.M., 
Professor of Geology, Mining and Metallurgy, in the Univer- 
sity of Wisconsin. 
In an Article on “The Age of the Quartzites, Conglomerates 
and Schists of Sauk County, Wisconsin,” published in this 
Journal for February of the present year (1872), I gave what 
I believe to be ample proof of the Pre-Potsdam age of the rocks 
then treated of. ese rocks, previously regarded by g 
authority (Winchell, Eaton, Percival), as having resulted from 
a metamorphism of the Potsdam sandstones, I then showed to 
have been outlying islands and reef ledges in the Potsdam seas. 
I stated also that there were several other outlying patches of 
metamorphic rocks, similar to these, and scattered at wide 
tances apart within the Lower Silurian area ; one of these I have 
since been able to examine with some care, and am prepar 
to say of the rocks found there what I did of those in the Sauk 
a region, viz: that they are undoubtedly Pre-Pots . 
The locality referred to is near the village of Portland, in the 
* See V. Meyer, Annalen der Chemie u. Pharmacie, clvi, 267. 
