Page:Popular Science Monthly Volume 13.djvu/574

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the whole character of the opening, indicated clearly that it should be attributed to some other animal than a teredo.

As to the unprepared pieces, there only remained small ends, which reached above the water. All the rest was converted into a spongy mass, which broke at the slightest effort.

The experiment with the creosoted oak was less satisfactory. In all the pieces were found, here and there, galleries of the teredo, but always in small numbers; in sawing the wood, it was found that the injuries were invariably in those parts where the color showed that the oil had not been able to penetrate. Although, as far as is known, no effort has been made elsewhere to preserve oak from the teredo, the commission places great value upon experiments with this wood. In fact, for many marine works, oak cannot be replaced by any soft wood which absorbs creosote-oil easily. Hence, the commission has had creosoted at Amsterdam, by a newly-perfected process, some pieces of oak, which were exposed in 1864 at Nieuwe-Diep; these will not be examined until tested during three summers.[1]

Petroleum has also been recommended to the commission, but it was not deemed worth while to experiment with it, especially on account of its high price; even although petroleum should prove to be as efficacious as creosote-oil for protecting wood against the teredo, its price would prevent its use for that purpose.

Experiments with Exotic Woods, other than Ordinary Woods of Construction.—The commission has not been able to make many experiments in this direction. It acquired a certainty that the greenhart of Surinam, the bulletrie, the American oaks, and wood as hard as mamberklak, are not spared by the teredo. The commission received a large piece of the wood of guaiacum, which had been five or six years in the water at Curacoa, and was found to be entirely eaten by the teredo—an evident proof that even the hardest woods are not safe from the attacks of that mollusk.

The commission has received, it is true, many communications relative to different kinds of woods known to be poisonous to fish, but it has not had an opportunity to experiment with them. We await some light on this point, from researches which the Government has ordered to be made at our possessions in both the East and West Indies.

Conclusions.—By way of recapitulation, the results of the experiments, tried by the commission during six consecutive years, were as follows:

1. The different coatings applied to the surface of wood, with the design of covering it with an envelope on which the young teredo cannot attach itself, offer only an insufficient protection; these coverings are likely to be injured either by mechanical means, such as the action of the water, or by being dissolved by the water. Just so soon as

  1. American oaks of coarse, open fibre are easily impregnated.—Translator.