APRIL, 1902. SOME RECENT OBSERVATIONS ON MIGRATION OF BIRDS. 
107 
the topography of the surrounding country has much influence 
upon the number of birds flying. In each of the Beloit hues the 
sudden enormous rise of the hues marks the time when the tele- 
scope pointed directly down the course of the Rock River. In 
Madison the same feature is true. During four years of observa- 
tion the greatest flights were obtained when the telescope pointed 
over the Madison Lakes and Yahara River system. The topo- 
graphy surrounding Lake Forest, Ann Arbor and Detroit, has not 
yet been studied sufficiently to enable us to say what the condi- 
tions are at these places. 
Another form into which the observations will be placed is 
that illustrated by Plate II. We have here a number of circles 
each representing the field of vision during a certain period of 
time. Each line in the circle represents the flight of a bird, the 
lightly shaded end shows the place of entrance into the field of 
vision, the other the exit, and the dotted lines birds that were so 
close to the telescope that- they appeared out of focus. The ar- 
rows outside of the circles show the general direction of flight for 
the period. This makes a most serviceable form into which to 
place these data. , 
One special feature noticeable on the accompanying plate (II.) 
is the two main directions of flight, with the predominance of the 
one in April and the other in May. This would seem to indicate 
two distinct migratory routes passing through Madison. Indeed 
other observations seem to indicate that this is actually the case. 
It is not the object of this preliminary report to discuss gener- 
alizations. The foregoing considerations have been given merely 
to show the trend of the work and somthing of the results we mav 
expect to attain from this method of observation. The telescope 
certainly offers an excellent field for research to the student of 
ornithology, and it is to be hoped that in the near future it may be 
brought into operation over a larger territory. 
