%n augmenting the Specific Gravity (fi different Woods, 365 
time the marine-driver^, and its attached pieces were under wa- 
ter, by the way of distinguishing the degree of impregnation 
produced by pressure, from the absorption which takes place 
from simple immersion. On being brought up, they were all 
specifically heavier than sea-water ; and, when compared with 
the counterparts, the clear elfect of impregnation by pressure, 
was found to be 302 grains in the fir and hickery, and 316 
grains in the ash. This experiment was repeated im lati- 
tude 78° 2', on the 7th June 1817, by the immersion of twelve 
articles of different shapes and sizes, to the depth of 4566 feet. 
On this occasion, the apparatus was 30 minutes on its way 
down, rested 40 minutes, and took 36 minutes in drawing up, 
being altogether 106 minutes under water. The degree of im- 
pregnation produced on each of the different substances used in 
this experiment, is stated in the following Table. 
Names of 
Substances. 
Shape. 
Solid Con- 
tents. 
Specific Gra- 
vity after 
Immersion.. 
Proportion of 
Weight gained 
per Cubic Inch 
in consequence 
of Pressure. 
Hickery 
Elm 
Beech 
Fir 
Mahogany 
Lign. Vitae 
Bone 
Wedge 
Rectang. prism 
Ditto 
Thin wedge 
Parallelepiped. 
Rectang. prism 
Ditto 
Cub. Inch, 
1.4436 
2.0040 
2.0040 
0.9505 
0,8792 
1.9356 
0.1380 
W. 60°.1000 
1.1760 
1.1321 
1.1806 
1.1168 
1.0523 
1.3315 
2.1372 
Drams Avoir. 
4.606 
5.639 
4.790 
4.050 
3.071 
0.336 
0.725 
This degree of impregnation is not surprising, when we 
consider that the pressure of water, at the depth to which these 
specimens of wood were sent, is equal to, at least, 2031 lb. or 
18 cwt. 15 lb. on every square inch of surface. 
These experiments were repeated on the 18th July 1818. 
Finding, on former trials, that pieces of fir wood sent down 
4000 feet, were more impregnated with sea-water than others 
immersed only half that depth, I was in hopes that the degree 
of impregnation of similar pieces of the same kind of* wood 
might be applicable as a measure of depth. If this were the 
VOL. I. NO. 2. OCTOBEM 1819. B b 
