M. Duvaucel, likewise, affirms that the cry of the Siamang may be heard for miles--making the woods ring again. So Mr. Martin[15] 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 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. There is good testimony that various species of Gibbon readily take to the erect posture. Mr. George Bennett,[16] a very excellent observer, in describing the habits of a male _Hylobates syndactylus_ which remained for some time in his possession, says: "He invariably walks in the erect posture when on a level surface; and then the arms either hang down, enabling him to assist himself with his knuckles; or what is more usual, he keeps his arms uplifted in nearly an erect position, with the hands pendent ready to seize a rope, and climb up on the approach of danger or on the obtrusion of strangers. He walks rather quick in the erect posture, but with a waddling gait, and is soon run down if, whilst pursued, he has no opportunity of escaping by climbing.... When he walks in the erect posture he turns the leg and foot outwards, which occasions him to have a waddling gait and to seem bow-legged." Dr. Burrough states of another Gibbon, the Horlack or Hooluk: "They walk erect; and when placed on the floor, or in an open field, balance themselves very prettily, by raising their hands over their head and slightly bending the arm at the wrist and elbow, and then run tolerably fast, rocking from side to side; and, if urged to greater speed, they let fall their hands to the ground, and assist themselves forward, rather jumping than running, still keeping the body, however, nearly erect." Somewhat different evidence, however, is given by Dr. Winslow Lewis:[17] "Their only manner of walking was on their posterior or inferior extremities, the others being raised upwards to preserve their equilibrium, as rope-dancers are assisted by long poles at fairs. Their progression was not by placing one foot before the other, but by simultaneously using both, as in jumping." Dr. Salomon Müller also states that the Gibbons progress upon the ground by a short series of tottering jumps, effected only by the hind limbs, the body being held altogether upright. [Illustration: FIG. 8.--A Gibbon (_H. pileatus_), after Wolf.] But Mr. Martin (l. c. p. 418), who also speaks from direct observation, says of the Gibbons generally: