370 TEREDO NAVALIS IN NOVA SCOTIA — MURPHY. 
costiy ; for, to really protect wood in this way, it is important 
that the square heads of the nails join exactly ; for insuring the 
best results, the armoured piles are exposed in the open air for 
some time before being placed in the water, that rust, forming 
on the surface of the iron, may close up the interstices inevita- 
bly remaining between the heads of the nails. But this precaution 
is not infallible, as the Commission examined piles more than 
once, in the course of its investigation, which had been several 
years in the water, and whose surface was entirely incrusted 
with rust more than a centimetre thick, but which were, never- 
theless, eaten in the interior by the teredo. 
Impregnation of wood with different. substances. The Com- 
mission examined in this category the following methods: 
1. Sulphate of Copper. 
2. Sulphate of Protoxide of Iron (Green vitriol). 
3. Acetate of Lead. 
4. Soluble Glass and Chloride of Calciuin. 
5. Oil of Parafine. 
6. Oil of Creosote. This is, as is very well known, a product 
of the dry distillation of coal tar, separated by distillation from 
the more volatile parts, which serve for the preparation of ben- 
zole and naptha, the residuum being pitch. Experiments had 
already been tried abroad, as well asin Holland, with this sub- 
stance, and from the beginning of their experiments the Com- 
mission paid especial attention to this very important method of 
preparation. 
Wood of various kinds, prepared with creosote oil, at the 
works of the Society for the Preservation of Wood, at Amster- 
dam, was placed in the sea in the month of May, 1839, at Fles- 
singue, Harlingin, and Stavoren, the pieces of oak, pine and red 
fir, were found intact, while those unprepared were perforated. 
In the month of October, of the same year, the pieces of creo- 
soted pine and fir at Harlingin showed a perfect state of preser- 
vation. At Harlingin the treated and untreated pieces were fas- 
tened together; the teredo penetrated the latter, but had not 
touched the creosoted wood. The same was true of the creasoted 
wood at Stavoren, when visited in 1859. 
