A treatise on the origin, progress, prevention, and cure of dry rot in timber

by Thomas Allen Britton

“2nd. Impregnation with soluble metallic salts generally considered poisonous to animals does not preserve the wood from the invasions of the teredo; the failure of these salts is partly attributable to their being soaked out of the wood by the dissolving action of the sea-water, partly also to the fact that some of these salts do not appear to be poisonous to the teredo.

“3rd. Although we cannot venture to say that there may not be found in the colonies a wood that may resist the teredo, yet we may affirm that hardness of any timber is not an obstacle to the perforations of this mollusc. This has been proved by the ravages it has made on the Gaïac and Mamberklak woods.

“4th. The only means which can be confidently regarded as a preservative against the ravages of the teredo is the creosote oil; nevertheless, in the employment of this agent great care should be taken regarding the quality of the oil, the degree of penetration, and the quality of the wood treated.”

These results of the experiments of the committee are confirmed by the experience of a large number of engineers of ponts et chaussées (bridges and causeways) in Holland, England, France, and Belgium. For example, very lately a Belgian engineer, M. Crepin, expressed himself as follows in his Report, dated 5th February, 1864, upon experiments made at Ostend:

“The experiment now appears to us decisive, and we think we may conclude that fir timber well prepared with creosote oil of good quality is proof against the teredo, and certain to last for a long time. Everything depends, therefore, upon a good preparation with good creosote oil, and on the use of wood capable of injection. It appears that resinous wood is easiest to impregnate, and that white fir should be rejected.”

M. Forestier, the able French engineer at Napoléon-Vendée sums up as follows the results of the experiments undertaken by him in the port of Sables-d’Olonne, viz.:

“These results fully confirm those obtained at Ostend, and it appears to us difficult not to admit that the experiments of Ostend and Sables d’Olonne are decisive, and prove in an incontestable manner that the teredo cannot attack wood properly creosoted.”

It thus appears that there are three preservative methods, which, according to experience, will save timber piles from the ravages of the worms, viz.: 1st. By using woods able to resist unaided their attacks. 2nd. The mechanical method, which is, by covering the piles with scupper nails, &c. This process is, however, very expensive, especially as the four sides of the pile must be covered; and, moreover, it affords no protection to the timber from internal rot or decay. 3rd. The chemical, or “creosoting” method. This process is cheaper than the last; it preserves the wood from decay, and no worms will touch it.

When unprepared piles are placed in the sea, there is every probability, sooner or later, of their being attacked by the teredo. This animal, however, is not left in peaceable enjoyment of the dwelling which it has constructed, and the food which it loves, but is liable to be attacked by an enemy, an annelide, to which the late M. de Haan has given the name of Lycoris fucata. This animal is to be found wherever the teredo exists, indeed its eggs and larva are to be met with in the midst of those of the mollusc. M. Kater has remarked that the adult lycoris dwelling in the mud which it enters during winter, and into which the piles are driven, climbs up the pile to the hole formed by the teredo, where, in some manner, it sucks or eats its victim; then having enlarged the entrance to the hole, it enters and rests in the place of the teredo. After a time it goes back to the entrance, and commences to seek for fresh prey.