Here are what I found.

愿《英语背诵文选》的PDF文件还有一些中文的学英文网站，都是“scarcely touches the turf an instant”。

录音里听到的好象如菲教授指出的是：“scarcely touches the turf for an instant”。

下面这篇古狗到的引用原文里是“rarely touches
the turf even for an instant”。

(source: http://www.archive.org/stream/hummingbirds00ridgrich/hummingbirds00ridgrich_djvu.txt)

Buffon considers the Humming Bird " of all
animated beings . . . the most elegant in form and brilliant in color.
The stones and metals polished by art are not comparable to this gem
of nature. She has placed it in the order of birds, but among the tiniest
of the race maxime miranda in minimus; she has loaded it with all the
gifts of which she has only given other birds a share. Agility, rapidity,
nimbleness, grace, and rich attire all belong to this little favorite. The
emerald, the ruby, and the topaz glitter in its garb, which is never
soiled with the dust of earth, for, leading an aerial life, it rarely touches
the turf even for an instant. Always in the air, flying from flower to
flower, it shares their freshness and their splendor, lives on their nectar,
and only inhabits those climates in which they are unceasingly re-
newed."