The material of ancient waterlogged wood is so far degraded that it consists of a new substance, designated by the neologism Paleoxyle, in order to distinguish it from ordinary wood. The new method of treatment comprises two successive phases: first, a series of chemical reactions which precipitate solid, insoluble products in the woody mass, then impregnation with linseed oil which hardens in the interior of the parenchyma by oxidative polymerization. The paleoxyle, thus treated, becomes very hard, incombustible and not liable to putrefaction, but the form and dimensions of the original object are perfectly conserved. This method requires only simple equipment that is easy to set up, and is not difficult. A large scale trial of the method is under way: treatment and reconstitution of a complete Roman wreck.