UNLIMITED Audiobooks and eBooks

Over 40,000 books & works on all major devices

Get ALL YOU CAN for FREE for 30 days!

A Quantitative Study of the Nocturnal Migration of Birds

George H. Lowery

No ratings yet

How does All You Can Books work?

All You Can Books gives you UNLIMITED access to over 40,000 Audiobooks, eBooks, and Foreign Language courses. Download as many audiobooks, ebooks, language audio courses, and language e-workbooks as you want during the FREE trial and it's all yours to keep even if you cancel during the FREE trial. The service works on any major device including computers, smartphones, music players, e-readers, and tablets. You can try the service for FREE for 30 days then it's just $19.99 per month after that. So for the price everyone else charges for just 1 book, we offer you UNLIMITED audio books, e-books and language courses to download and enjoy as you please. No restrictions.

Book Excerpt: 
. . .Great Cone below the maximum ceiling at which birds fly, a much smaller cone, which I shall refer to as the Cone of Observation (Figure 1).


Fig. 1. The field of observation, showing its two-dimensional aspect as it appears to the observer and its three-dimensional actuality. The breadth of the cone is greatly exaggerated.


Fig. 2. Method for determining the diameter of the cone at any point. The angular diameter of the moon may be expressed in radians, or, in other words, in terms of lengths of arc equivalent to the radius of a circle. In the diagram, the arc between C and E, being equivalent to the radius CO, represents a radian. If we allow the arc between A and B to be the diameter of the moon, it is by astronomical calculation about .009 radian, or .009 CO. This ratio will hold for any smaller circle inscribed about the center O; that is, the arc between A´B´ equals .009 C´O. Thus the . . . Read More