82 Mr. Gilbert Bufnett on the Decay 



substances, consists in a change occurring in the contents of their 

 intimate cellular structures, by which the matter therein con- 

 tained is either dissolved and carried away, leaving the cells 

 more or less empty ; or decomposition, and the formation of new 

 chemical combinations, is favoured, by which the quality of the 

 wood, or whatever it may be, becomes essentially altered. By. 

 maceration in different menstrua, the matter deposited may be 

 dissolved, and the cellular structures thus exhibited aflford a 

 number of very beautiful anatomical preparations : and thus it 

 happens in natural as well as artificial processes, that vegetable 

 substances kept perfectly dry or immersed in menstrua, in 

 which their peculiar matters are insoluble, or which, instead of 

 favouring, check their proximate principles from undergoing 

 decomposition, and producing new compounds, will last un- 

 hurt, or but little changed, for ages ; but if the matter be 

 soluble in the menstruum applied, or the reverse of the former 

 circumstances occur, then solution and decomposition, that is, 

 decay will, more or less, rapidly ensue. 



Timber exposed to atmospheric changes is subject, more or 

 less, to all these influences, and those woods, the ligneous mat- 

 ter of which is the most soluble in water, will, cceteris paribus,- 

 the most speedily decay ; but it often happens, that the de- 

 composition (as in fossil timber) produces a matter less cor- 

 ruptible than the original, at least on the outer surface, and 

 thus defends the internal parts — sometimes the whole becomes 

 thus changed. More frequently, however, the decompositions 

 that take place, generate various gases, e. g., carbonic acid 

 carburetted hydrogen, &c., &c., in abundance, the elasticity 

 of which cannot fail to rupture the delicate tissues of which 

 the cells are formed ; and these fissures, minute and almost 

 inappreciable as they may be thought, in fact are potential 

 capillary tubes : moisture is again applied, is again absorbed, 

 and by these means pervades the intimate structures, even 

 more readily and more extensively than before. By sea-water, 

 salts are also carried in, which often crystallize ; or during 

 cold weather the water freezes, and either of these processes 

 will sufficiently account for many of those cracks and fissures, 

 which do not occur from violent exsiccation. The solution 

 and deposit is sometimes so complete and general, as to trans- 

 fprm a block of wood into stone, as may be seen in almost 

 every museum ; and the fissures just noted, which are always 



