The forests contain a great variety of useful woods, affording excellent timber; among the commonest trees are the yellow wood, which is also one of the largest, belonging to the yew species; black iron wood; heavy, close-grained and durable stinkhout; melkhout, a white wood used for wheelwork; nieshout; and the assegai or Cape lancewood.
In wheelwork of this kind the contact of each pair of teeth commences at the foremost end of the helical front, and terminates at the aftermost end; and the helix is of such a pitch that the contact of one pair of teeth shall not terminate until that of the next pair has commenced.
Trains of Wheelwork.Let A1, A2, A3, &c., A,,,_1, A,,, denote a series of axes, and aj, a1, a3, &c., a,,,1, a,,, their angular velocities.
Alexander Bain in 1846 suggested enclosing the wheelwork in the rotator.
In Thomas Walker's harpoon or frictionless log, introduced in 1861, the wheelwork was enclosed in a cylindrical case of the same diameter as the body of the rotator or fan, and the latter was brought close up to the register, forming a compact machine and avoiding the use of the 6-ft.