V0L f 9 fo XVI1 ] General Notes. 605 



speed was 11.5 meters per second. It was quite noticeable that the birds 

 were being blown off-course, because of the lack of similarity between the 

 direction in which they were headed and the direction in which they were 

 progressing. 



Emphasis should be given to the good fortune in having two factors 

 known within narrow limits: the altitude of the cloud bases, and the near- 

 ness of the birds' levels to the cloud bases. I may add that on rare occa- 

 sions birds pass singly across the field of the theodolite, but no instance 

 of such numbers being visible in the field at one time has ever been my 

 experience in following balloons during the past two years. 



It should be remarked that there is little by which to identify the kind 

 or even the type of bird observed. The mean diameter of the balloon 

 was .71 centimeters, and it is estimated that the spread of a single wing 

 of one of the birds would have completely covered the balloon. There 

 seemed to be moderate length of neck, little or no length of tail, and 

 no distinguishable trailing legs about these birds. The main point of 

 interest probably is the determination beyond question of the rate of 

 speed maintained by birds evidently flying with a fixed objective in flock 

 or group formation. 



I would add that the further observation of these birds would have 

 been carried out had time permitted, but as the immediate despatch of 

 upper-air data computed from the balloon run is of great urgency it was 

 necessary to bring the theodolite sighting to a close. 



The kind assistance of Mr. B. B. Whittier, Observer U. S. Weather 

 Bureau, who checked and corroborated the readings is gratefully ac- 

 knowledged. — C. G. Andrus, Observer, U. S. Weather Bureau, Lansing, 

 Mich. 



