The toothed wheels give a slightly better efficiency, but the worm gear is somewhat smoother in its action and entirely silent; the noise of gearing can, however, be considerably reduced by careful machining of the teeth, as is now always done, and also by the use of pinions made of rawhide leather or other non-resonant material.
When quick-running metal pinions are used they are arranged to run in closed oil-baths.
Leather pinions must be protected from rats, which eat them freely.
On such lines the beginning of a rack section is provided with a piece of rack mounted on springs, so that the pinions of the engine engage smoothly with the teeth.
For example, on the surface of a shibuichi box-lid we see the backs of a flock of geese chiselled in silver, and when the lid is opened, their breasts and the under-sides of their pinions appear.