of constructing ships in the mercantile navy. 135 
Found defective, but very generally to have communicated 
their own decay to the timbers to which they are attached. 
Besides this, the grain of the rib-pieces being much cut, to 
give them the curvature required, has a considerable share in 
weakening the general fabric. That they occasion a great 
consumption of materials, is obvious, as the ends of the two 
rib-pieces must first be cut away, and then be replaced by the 
chock. 
This mode of putting together the frame, is also peculiar 
to the English ship-builder ; and I find, from an old work in 
my possession, dedicated to George the First, that the prac- 
tice was introduced in the construction of English ships about 
the year 1714 ; and having heard that so unfriendly to it was 
the builder (Mr. Naish) of the Royal William, that he re- 
fused to adopt it ; and being desirous of ascertaining the fact, 
when that ship was taken to pieces at Portsmouth, in 1813, I 
found that she was built without the wedge pieces or chocks, 
to which, in a certain degree, I ascribe her strength and dura- 
bility ; her ribs being by her structure less grain-cut, and 
for want of chocks, less liable to decay in those parts where 
they are inserted. 
The introduction of chocks, was no doubt to procure that 
curvature which is so necessary in the formation of a ship, 
when crooked or compass timber became scarce; as may be 
seen by PI. VIII. Fig. 2. which describes the shape of a piece 
of timber in the converted form ; and by which it will also be 
seen, that the introduction of the chocks assists in obtaining the 
required curve. But this curve may equally be obtained by 
a different combination of materials, and at a considerable 
less consumption of useful timber. 
