years in the Eastern Archipelago, and to the results of whose personal
experience I shall frequently have occasion to refer, states that the
Gibbons are true mountaineers, loving the slopes and edges of the
hills, though they rarely ascend beyond the limit of the fig-trees. All
day long they haunt the tops of the tall trees; and though, towards
evening, they descend in small troops to the open ground, no sooner do
they spy a man than they dart up the hill-sides, and disappear in the
darker valleys.

All observers testify to the prodigious volume of voice possessed by
these animals. According to the writer whom I have just cited, in one
of them, the Siamang, "the voice is grave and penetrating, resembling
the sounds goek, goek, goek, goek, goek ha ha ha ha haaaaa, and may
easily be heard at a distance of half a league." While the cry is being
uttered, the great membranous bag under the throat which communicates
with the organ of voice, the so-called "laryngeal sac," becomes greatly
distended, diminishing again when the creature relapses into silence.

M. Duvaucel, likewise, affirms that the cry of the Siamang may be heard
for miles--making the woods ring again. So Mr. Martin* describes the
cry of the agile Gibbon as "overpowering and deafening" in a room, and
"from its strength, well calculated for resounding through the vast
forests." Mr. Waterhouse, an accomplished musician as well as
zoologist, says, "The Gibbon's voice is certainly much more powerful
than that of any singer I have ever heard." And yet it is to be
recollected that this animal is not half the height of, and far less
bulky in proportion than, a man.

[footnote] *'Man and Monkies', p. 423.