98 BULLETIN OF WISCONSIN NATURAL HISTORY SOCIETY. VOL. 2. NO. 2. 
directions were sent to all who expressed their willingness to 
assist : 
BIRD MIGEL\TION. 
Directions for Observing with Telescope. 
The Instrument. 
Should be one with an objective ranging somewhere between 
2 and 6 inches. The eye-piece should be supplied with 2, or ii 
possible 4, hair-lines crossing in the center, thus dividing the field 
of vision into quadrants or octants. 
Time of Observation. 
Begin to observe as soon as the moon is high enough to come 
distinctly into the field of vision, and continue until morning. 
To Begin the Observations. 
Focus the telescope on the moon with the point of intersection of 
the hair-lines on the moon's center. Turn the eye-piece so that one 
of the lines lies parallel to the direction in which the moon is mov- 
ing across the heaven. Xow turn to your note paper. At the head of 
this write the date, locality, direction of wind, and weather in gen- 
eral. Just below this draw a circle, putting in the hair-lines as 
they appear through the telescope. Number them, beginning at the 
right hand side of the one you have placed parallel to the direction 
of the moon and continuing counter clock-wise. See figure 
below : 
The Observations. 
(It is a difficult task to observe and write out the observations 
at the same time, and, also, it will tire the eyes to look at the bright 
moon too long at one stretch. It is, therefore, advisable to have 
two observers so as to relieve each other every half hour or even 
every fifteen minutes, the one writing the observations while the 
other is' observing) . 
The time should be divided into periods of fifteen minutes 
each, i. e. the observations should be made for periods of this 
length. 
The following data should be noted wuth every bird that crosses 
the field of vision : 
The number and approximate tenths (as indicated by the hair- 
lines ) at which the bird enters and likewise at which it leaves the 
field of vision. 
The speed at which it is flying — slow, fast, like a shot, etc., etc. 
