of constructing ships in the mercantile navy. 141 
the timbers. When filled in to within about two inches of 
the surface of the frame, the pieces of three inches already 
fitted and taken out, are to be well driven in and caulked, 
and by so doing, no space will be left unoccupied. If con- 
sidered desirable, these pieces may be driven below the sur- 
face of the timber, thereby leaving water courses to convey 
the leakage to the pumps in channels. And prior to launch- 
ing or undocking of ships, built on the principle I have re- 
commended, it has been the practice to inject the part filled 
in with mineral tar, by means of a simple forcing pump, 
boring holes in the joints of the timbers for the introduction 
of the pipe. By following this method, the air will be ex- 
cluded, which, as experience has shown, tends much to the 
durability of the fabric ; confirming the assertions made by 
Doctor Hales on this subject, in his work on Ventilators, 
published in 1750, and also of Doctor Henry, in his work on 
the Elements of Chemistry. If what is here recommended 
be attended to, and mercantile ships were built under roofs, 
as ships of war now are, durability would be obtained in ad- 
dition to safety, from the mode of their construction. 
The beams are to be attached to the sides, as shown at O, 
PI. IX. Fig. 5. rendering wood knees unnecessary, and re- 
quiring only a small number of those of iron. 
PI. XI, marked P, describes the old principle of framing 
the stern with transoms. Q, the new principle, with timbers 
similar to the bow, omitting the transoms below the wing or 
upper transom ; and by introducing the new principle on 
which the floors are made, the necessity of using valuable 
compass, or crooked timber, hitherto required, and with 
MDCCCXX. U 
