ee, 294 General Notes. | March > 
however, shows that they all differ materially from each other, 
and must be referred to three separate families, viz., the Python- 
idz, the Boidz and to the new family of the Charinide. The 
= definitions of these families are as follows: 
Supraorbital, postfrontal and coronoid bones present......--sseeeeeses Pythonide. 
Postorbital and coronoid bones present; no supraorbital. .......>.....0.% oide. 
Neither postfrontal, supraorbital nor coronoid bones present Charinide. 
—E, D, Copi: 
NOTE ON THE PROBLEM OF SoarING Birps.—In the interest- 
ing paper on soaring birds, by I. Lancaster, published in Nos. 
11 and 12 of the Naturatisr for 1885, the writer attributes the 
power which is utilized by the bird, no doubt correctly, to the 
condensation and expansion of the atmosphere, produced by the 
relative motion of the bird with respect to the atmosphere. 
An evaluation, if it were practicable, of the excess of the 
upward, above the downward, atmospheric pressure upon the bird, 
when it soars horizontally or remains stationary on fixed wings, 
would show, no doubt, that such excess is exactly equal to the 
weight of the bird; and the rear expansion on a vertical section 
of a bird that remains stationary on fixed wing in a current of aif; 
ko would be found to be exactly equal to the force exerted by the 
breeze. No other explanation of the phenomenon is conceivable, 
and this is substantially the explanation suggested by Mr. Lan- 
-vertical descent, 
_. This is obviously a misinterpretation of the phenomena ; for 
-itis well known that the upward lateral force would arrest the 
downward motion, so that the cause of the upward motion woul 
be immediately withdrawn ; and besides, it leads to the absurd con” 
“clusion that the secondary effect of gravitation, through the com 
- action. 
; Obviously the best the bird can do to sustain his elevation m 
still air, will be, by suitable position of his wings, to effect a 5#¢ 
_cession of descents and ascents, thus utilizing, not only the con- 
-densation produced by his descent, but also the momentum 
_ acquired by his velocity. | 
it es pees ge ee Fi EA p aes 
ha fia eerie fier uke NU aCe = ST SS I L E 
_ densation and expansion of air, may exceed that of its direct 
AREN OSS Lemos Pe ee ey a 
