328 On the Dry-Rot in Timber. 



case it mav be said, dry-rot circulation inevitably takes place 

 between tliem. Humidity or moisture acts, by assimilating the 

 particles of its gravitalijig base, with those of the gravitating base 

 of the wood ; no that when the external air is of such a nature 

 as to attract any of these particles, or to attract any element to 

 which they may be united, the wood and water together part 

 with their common gravitating element. The consequence of 

 which is, that the water being decomposed disappears, and the 

 wood has lost its ponderable base. Hence it is obvious, how it 

 is that water is indispensable to promote dry-rot ; why its de- 

 composition is to be guarded against; and why wood, when dry- 

 rotted, is always perfectly free from water, and also devoid of 

 weight. 



The medium of air, which surrounds wood wholly or in part, 

 is as much accessary to dry-rot circulation, as it is to that of the 

 galvanic pile. In the latter case, chemical elements are alone 

 given off, and oxygen gas promotes the circulation : whereas 

 with wood, the air in which oxygen is deficient favours circula- 

 tion best ; and it likewise is the contrary or ponderable base only 

 which escapes. The medium of air which makes fungi shoot, 

 cannot l)ut be the means of exciting dry-rot circulation : some- 

 times, (as the formation of fungi depends on the nature of the 

 juices of the wood,) these formations may contribute to the rot 

 by assisting circulation at its commencement : but without 

 fungus appearing at all times or being any way indispensable, 

 drv-rot circulation may take place. 



The piiKVENTiVE to dry-rot circulation, it follows, consists in 

 insulating every piece of timber, or surrounding it like a gate- 

 post, with a medium similar to atmospheric air; or by both ap- 

 plications, according to the situation of the piece. In general, 

 tliose parts onlv of the surfaces of the wood which are in contact, 

 and tliose which are in contact with confined air, are such as 

 have the rot, and for limited distances ; which show the mutual 

 action which prevails, where it originates, and the direction it 

 takes; also the medium which favom-s the circulation, and that 

 which does not excite it. Every piece of timber should be in- 

 sulated fiom another, by means of some non- attracting disc be- 

 ing fixed between. No single or insulated piece will ever be 

 found capable of galvanising itself. The insulating matter should 

 be such as cannot be readily removed or rubbed away, as is the 

 case with unctuous substances. Wherever confined air may 

 have opportunity to remain, it should be kept out; as we find 

 light wainscots rot on the wall side, having confined air or air 

 deficient of oxygen between : whereas in buildings, all kinds of 

 wood-work are preserved, that are deprived of this deleterious 

 medium by being imbedded in mortar. For which reason, the 



recent 



