504 
SYLV1AD.15. 
ease against tlie perpendicular face of walls or rocks, by means of its 
strong toes and hooked claws, which are disposed in a totally dift’erent 
manner from those of all other genera.” * 
By the middle of August these wholly disappear, which is a month 
or six weeks before the other species. It is said to inhabit the greater 
part of the old continent, and has been found in some parts of America, 
and at the Cape of Good Hope. 
SWIMMING OF BIRDS. — The superior velocity with which 
aquatic birds swim under water has not wholly escaped notice ; but it 
is not entirely produced by the action of the wings, which are some- 
times used as fins to accelerate the motion, but is occasioned by the 
pressure of the water above. In swimming on the surface, a bird has 
two motions ; one upward, the other forward, at every stroke of the 
feet ; so that when covered with water, that force which was lost by the 
upward motion is all directed to the progressiv-e, by which it is enabled 
to pursue its prey, or to escape an enemy with incredible speed. The 
otter and water rat swim much faster under water than they do upon 
the surface. 
SWINE PIPE. — A name for the Red Wing. 
SYLVIA (Latham.) — *Warbler, a genus thus characterised. Bill 
slender, rather awl-shaped, and straight ; but with the point of the 
upper mandible slightly bent and notched ; lower mandible straight ; 
base more high than broad ; nostrils at the sides of the base oval, 
and partly covered with a membrane ; legs having the shank longer 
than the middle toe ; toes three before and one behind, the outer toe 
being joined at its base to the middle one ; wings with the first quill 
' very short, sometimes indeed wanting ; the second and third nearly of 
equal length ; wing coverts and scapulars short. * 
SYLVIADAii (Vigors.) — Warbler kind, a family of Perchers, 
(^Insessores, Vigors.) 
