[1]There is a wonderful performance daily
exhibited in southern climes and occasionally seen in northerly
latitudes in summer, which has never been thoroughly explained. It is
the soaring or sailing flight of certain varieties of large birds who
transport themselves on rigid, unflapping wings in any desired
direction; who in winds of 6 to 20 miles per hour, circle, rise,
advance, return and remain aloft for hours without a beat of wing, save
for getting under way or convenience in various maneuvers. They appear
to obtain from the wind alone all the necessary energy, even to
advancing dead against that wind. This feat is so much opposed to our
general ideas of physics that those who have not seen it sometimes deny
its actuality, and those who have only occasionally witnessed it
subsequently doubt the evidence of their own eyes. Others, who have seen
the exceptional performances, speculate on various explanations, but the
majority give it up as a sort of "negative gravity."
