464 Scientific Intelligence. 
reason that fossils, the only true criterion of geological age, are 
absent from the yeds, and from all underlying beds; he says, 
accordingly, only this—older than the Potsdam sandstone and its 
equivalents. The Cambrian of Great Britain is of great thick- 
ness below the equivalents of the Potsdam sandstone ; and the 
question has arisen among those who have considered the subject, 
whether the Keweenian beds are not the equivalents of the part 
of the Cambrian below the oem Lingula flags, that is, of the 
Lower Cambrian and Menevian groups of Great Britain, or of 
the Lower Cambrian alone. Should either prove to be a fact, 
the series is true Cambrian; and if the name Cambrian is to be 
used at all in American geology, this series may claim it better 
than any beds of later origin. 
The colored maps of the Report are of the best style of the 
er and nee a illustrations are excellent. 
Note the Par a sal oe nlm the Hornblende of the 
Onatalline. ‘Roske of the Northw by R. D. Irvine.—In my 
second paper on this jahiots in nem * Journal for February, 1884, 
in which I give an historical review of the matter, there is a 
quite important omission. In referring to the work of Streng on 
the Minnesota crystallines I failed to note that, besides the Du- 
23 gabbro, Streng had described other rocks from Minnesota* 
n a number of which he found associations of augite and diallage 
with hornblende, of such a nature as to lead him to believe in the 
secondary origin of the latter. It is evident that Streng was by 
far the first to note this relation betweer hornblende and an aug- 
itic material in the rocks of the Northwest; not merely in green- 
stones sind in ype and other quartz-bearing r rocks. ‘And ae 
ie in 
beider Mineralien ist eine so un patie A die Hornblende 
dringt in so schmalen Paithien i in die Augitsubstanz ein, dass man 
sich des Gedankens nicht erwehren kann, hier sei die Hornblende 
aus beyme agit rac ag Der Beweis fir bait’ ~aemer i wird 
sich trigt. Wiirde Masia Beweis Heo dann ae man 
annehmen miissen, dass auch andere el nblenden, welche keinen 
Augitkern mehr besitzen, aus Augit entstanden sein und dass bei 
ihnen die Umwandlung schon vollendet sei; d. h. dass die 
thy HE Geese einstmals noch reicher an augitischem } aie 
ale gewesen sein, - sie jetzt erscheinen.” This was in 1876. 
Madison, Wis., Oct. 7, 1884. 
* Neues Jahrbuch fiir Adit ete., 1877, pp. 31-56, 113-138, 225-242. 
cutee Jahrbuch, 1877, p. Mages See also for translation Eleventh Annual 
rt Geol. Survey Minn., p. 8 
