78 S. F. Baird on North American Birds. 
years from 1845 to 1851). At Philadelphia the annual progres- — 
sion, in 1843, was (44); more than double the annual inequality 
(2’). This must be attributed to the reponderating action of 
the currents traversing those localities at which the needle was 
est. 
magnetic intensity of the southern hemisphere, in high latitudes, 
and the aut. equi. currents that of the northern hemisphere; 
[To be concluded. ] 
Arr. XII.—The Distribution and Migrations of North American 
Birds ; by SpENcER F, Barrp, Asst. Sec. Smithsonian Insti- 
_ tution. (Abstract of a memoir presented to the National Acad- 
emy of Sciences, Jan., 1865.) 
5 Ahan ee te grey te es at eee Mere a 
Ir is well known to all students of Natural History, that the 
zoology of America or the new world is very different from that 
of the old world, and that with these two grand divisions, there 
are in each various subdivisions of greater or less importance. — 
— 3 ‘ support of most naturalists of the 
present day, and his details will ever mark an era in the science 
of zodlogical geograph 
eography. ee 
_ Dr. Sclater, in the article above alluded to, presents the follow- 
_. It should have been stated in the text (p. 67) that the rotation of the earth 
virtually shifts the point®f normal im the ether to the east of the 6 a.M- 
meridian ; and so delays the morning critical hours. ‘ 
.__\. © propose to discuss, very briefly, in the next No. of this Journal the remain- 
ing topic of our memoir,—Chemical Action. es ae got 
_* Journal of proceedings of the Linnean Society : Zoo ogy, ii, 1858, 130, (Read 
See Ss a ee ee 
