The leather, after this process, is soaked in petroleum or carbon bisulphide containing a little India-rubber solution, and is finally washed with petroleum benzoline.

Should the mixture be found to be too thick, it is thinned down with benzoline spirit until it is about the consistency of molasses at the ordinary temperature.

The oil issues from the rocks, or is drawn from subterranean reservoirs, where its presence is supposed to result from natural distillation of vegetable and animal substances, and after refining, put in the market as benzoline, paraffin, and lubricating oil.