•SS The American Gc(AogisL jimuHiy, isn;; 
PERSONAL AND SCIENTIFIC NEWS. 
The MiOHiGAX Geological Strvey. — After a <'«uiatose state 
for ten years, the -'-Board of (jeological Survey'' -of Michigan has 
presented a report to the Legislature. Dr. M. E. Wadsworth, 
Director of the Michigan Mining School at Houghton, is state 
geologist and has the assistance of various raeml)ers of his faculty. 
The report is a provisional one on the iron, gold, and cf)pper dis- 
tricts of northern Michigan. In addition to this there is nearly 
ready for pnl)lication. Vol. o, in the series of linal reports, con- 
taining the geology of the Marquette disti'ict, the report of Dr. (\ 
Kominger, and that on the gas and salt wells of the state. 
According to Major- General Drayson, of the Royal Artil- 
ler}', the earth has a tliircl rotation, which causes the half-axes of 
dail}' rotation to trace cones during a period of aliout 31,fi0(l 
years. He concludes that the glacial periods depend upon this 
third motion, and that they recur once in about 20,000 years, 
whilst the last terminated about (i.OOO years ago. The extreme 
variation of the poles amounts to al)out 12 degrees. The arctic 
circle encroaches on the temperate latitudes, and the tropic of 
Cancer varies the same amount toward the poles. The positions 
of these extremes determine the differences between summer and 
winter, (xeneral Dra3'son supposes a glacial epoch supervenes 
when the difference is at maximum, coincident with the pole of 
the heavens and the pole of the ecliptic in the same colure: and 
that the minimum of this difference, which marks the mild (or 
interglacial) epochs, will l)e reached in aliout the year 2295. A. 
1). The work, '■Untrndihn tjinmul in (istrnnomi/ nntl 'J''"^'>'J!I- 
discussing this theorv is i)ublished b}' Chapman and Hall, and 
Paul, Trubner&Co. . London. 
Wisconsin Academy of Sciences, Arts and Letters. The 
program of the twenty-third meeting held December 29th and 
iJOth. at Madison, contained the following geological titles: 
On the geology of the Waterloo (|uartzite sirea. 1. 31. Biiell, Eeloit ; 
notes on early lead mining in Wisconsin, 1\. G. Thwaites, Madison ; 
1 lie progress of Geological Investigations and Surveys of the state of- 
Wisconsin, ])articularly of ihe Lead Kegion — A Historical Review 
and Kibiiography (read by abstract); Notes on tlie structure of the 
ore dej)osits of southwestern Wisconsin, W. P. liiake, Sliullsburg; 
\'olcain'te, a new tyi)e of andesitic lava, AVni. H. Ilobbs and Louis 
Kalilenberg, INFadison. 
Dr. J. S. Newherrv. who has lieen professor of geology and 
paleontology in Columbia C(illege. New York City. fVn- twenty-two 
years, died at New Haven. Conn., Dec. 7, 1892. A future num- 
ber of the GEOLOf4TST will contain a suitable biographical sketch. 
