516 Gravitation and the Soaring Birds. [June, 
ity, as a separate force, was simply non-existent, for it never man- 
ifests its power but in connection with body, and the action of 
the body is our rule to determine the action of the force. 
It would be expected that in dealing with agencies of this kind, 
the greatest care should be exercised lest we fall into errors, and 
it is apparent that many of our notions in regard to gravitating 
bodies have been brought up from generalizations which do not 
include all the facts. The soaring birds have been omitted. To 
the extent of their exclusion our ideas are subject to error. It is 
imperative that they be brought under the dominion of gravity, 
and that the phenomena presented by them shall have due recog- 
nition in determining the characteristics of that force. 
-I have shown in the pages of this magazine that these birds 
_ Can be reduced to lower terms. A plane resting in air, and acte 
on by a force, exhibits all their activities, and up to this time, SO 
_ far as my knowledge extends, the mechanical world has failed to 
= work on elastic air. 
. ing propositions, which are self-evident on statement. = | 
_ otherwise noted, acceleration will be supposed to have termina 
2 ~ uniform motion progressing. 
recognize the facts eitubited by such a body, when subjected to 
