STRUCTURE OP WOOD, &C. 333 



science, and feel a gratification in being able to remove the veil ? a P an ? ? oIa " 



,,..,. . • > ,, tile parts in 



under which the mysterious operations of nature are concealed, wood. 



The particular object which I bad in view in exploring the 

 structure of wood, have led me by a way by no means likely 

 to be fertile in interesting discoveries • but I have begun the 

 work, and feel myself bound to complete it, in preference to 

 every other consideration. These fascinating researches, I am 

 aware, have already carried me too far, and I must now resign 

 them into the bands of others, in order to fulfil my engage- 

 ments. This T do most cheerfully, and it will give me the 

 greatest pleasure to behold a field too long neglected once 

 more broken up. 



Section IV. 



Of the Quantities of Water contained in Woods considered as 



dry, or Seer- Woods. 



Wood is an hygrometric substance, and when exposed to the 

 atmospheric air, always imbibes a visible quantity of water; 

 varying, however, with the temperature and humidity of the air. 



If the moisture in the wood were confined in vessels so con- 

 structed as to be totally impervious to watei, the fabric of the 

 wood would be uniformly the same, with the exception only of 

 the variations caused in its dimensions by change of tempera- 

 ture j in which case it would be very easy to determine the 

 quantity of water contained in the wood, when the specific 

 gravity of its solid parts was known. But as the bulk of all 

 woods is considerably diminished in drying, the experiment is 

 rendered rather prolix, though by no means difficult, and its 

 results are clear and satisfactory. 



A few examples will suffice to point out the method to be 

 pursued. 



The composition of the oak, in a growing state, at the be- 

 ginning of September has been already given. In order to 

 ascertain the change which this wood undergoes by the process 

 of drying, I made the following experiment. 



From a faggot of oak, 5\ inches in diameter, which, covered 

 with its bark, had been exposed to dry in the open air, for 18 

 months, I took a piece of rather more than an inch square, and 

 six inches in length j it was good fire-wood, and seemed very 

 dry. m 



This 



