100 BULLETIN OF WISCONSIN NATURAL HISTORY SOCIETY. VOL. 2. NO. 2. 
Wegemann, obtained three at Beloit, while Dr. Libby conducted 
the observations at Madison. The data received from Michigan 
deserve special mention for the care with which they were col- 
lected. 
One graphic representation illustrating tabulations of these 
data has been completed and will appear below. It is hoped that 
the other comparative tabulations will bring out points in the mi- 
gration of birds hitherto unknown. Beside the observations men- 
tioned above, Dr. Libby has recently turned over to the writer 
nine sets of data taken at Madison from April 9, 1898, to May 22, 
1899, and three tabulations of data taken at Madison in the fall of 
1897. This makes a total of 28 sets of data, comprising the obser- 
vation of over fifteen hundred individual birds. Since these data 
were collected at various times during four years and in different 
localities they should yield good results. 
It may appear to the inexperienced reader that little more than 
the direction of fight, the speed and size of a bird can be distin- 
guished by this method. There are, however, many features 
brought out with the help of the telescope, which, although of little 
value when taken separately, reveal many points of interest when 
brought together in the form of tabulation. Furthermore, it is not 
of rare occurrence that a species can be identified. 
The following tabulation will show in general something of 
what these data may yield : * 
BIRD MIGRATION AT DEi. GIT. 
Being situated on a wide river between Lake Erie and Lake 
Huron, Detroit should offer good facilities for the study of migra- 
tion. The following excellent summary of the observations taken 
at that place, together with the original data, was submitted by 
Mr. H. S. Warren : 
Data on Nocturnal Bird Migration. 
OBSERVATIONS TAKEN WITH THE TELESCOPE, W^ITH THE MGGN FOR 
A FIELD OF VISION. 
Detroit, Mich., May 13, 1900. 
Meteorological Data : Atmosphere, fair ; wind, light, southwest. 
Temperature : Max. 70 degrees at 8 p. m. ; min. 66 degrees at 
12 midnight. 
Time, 8:15 p. m. to 12 midnight, divided into periods of 15 
minutes each. 
