290 ON PREVENTING THE DECAY OF SHIPS. 



ships. Of late years the ends of ships' beams have been 

 charred, and the sound state in which they are now found 

 has justified and established the practice. Indeed all sub- 

 stances, that have undergone the action of fire, have been 

 proved to be unfavourable to the growth of the boletus lach- 

 rymans ; for, while stone has been rapidly destroyed by it, 

 well burnt briclis, in the same buildings, and in nearly the 

 same situation, have been free fron its attacks. 

 Fr«m the The scarcity of English oak, occasioned partly by the im- 



' ''■y*^!'/ ° ^^ proved state of agriculture, but more by the increased nuni- 

 have been em bers of our fleet, has obliged this country to have recourse 



ployed, ^Q wood grown in other states. The principal that have 



cUieHv imie. . ^ . . ' . _ ' 



been introduced in aid of oak are the varietie&of American 



pine: it becomes therefore of some importance to inquire, 

 ritch pine ge- which , sort of this timber i^ the moot durable, and which 

 •f,!e the soonest destroyed by vegetation. Pitch pme has been 



used by all nations in tlie construction of ships, and appears 

 nut the soon- to be very superior to every other species for general dura- 

 by full":. bility ; but this wood is the soonest destroyed by fungi, as 



these plants arc nourished by the great quantity of resin 

 contained in Its numerous cells. I have lately seen some 

 pitch pine plank of 7 inches in thickness completely de- 

 composed ; and, when cut open, the boletus was found to be 

 Very impro- vegetating in every part of it, but principally in the cells 

 j^a-'ls!^^ ^^^' wli'<^-^i were originally filled with resin. This proves how 

 improper it will be to employ it as treenail fastenings, on 

 •which the strength and safety of ships so much depend. 

 Pitch pme Pitch pine should not be covered with paint, as the pores of 

 painted. the wood are thereby stopped, and the expansion of the 



resin prevented, by which means the ligneous cells are 

 Preferable ap- broken, and decomposition takes place. The Americans 

 P'''*^'^"*' pay the top.sides ofthelr ships with a mixture of oil, resin, &c., 

 which are not unlike the substances that' are contained 

 in the wood they cover, and produce a hard varnish, imper- 

 vious to water. Perhaps the preparation recommended by 

 doctor Parry*, to prevent the dry rot, given in the Trans- 

 actions of the Bath and West of England Societies, might 



♦ It is mad« as follows : take 12 ounces of resin, 8 of roll brimetoue, 3 

 'g«lloxis of oil, and 4 ounces of bees wax: boil thera together, and lay 

 tbcn! on whil j hot. f See Journal, vol XIX, p, 337.] 



be 



