444 Inquiries relative to the Structure of Wood. 



We conclude from these results, that a young oak, in 

 a growing state, at the beginning of September, when 

 the wood appears to be diffused with sap, contains, nev- 

 ertheless, about a fourth of its bulk of air, and that its 

 solid ligneous parts do not make quite -fa of its bulk. 

 But we shall presently see that the lighter woods contain 

 still less of ligneous parts, and more of air, than the oak. 



A young Italian poplar, 3 inches in diameter, meas- 

 ured at 2 feet above the earth, was cut down on the 

 6th of September, while the tree appeared to be in a 

 growing state. The specific gravity of a piece taken 

 from the middle of the trunk was found to be 57,946; 

 consequently a cubic inch of this wood weighed 11.49 

 grammes. 



From a piece of this wood, apparently full of sap, 

 forty thin shavings were taken, 6 inches in length' and 

 half an inch broad. The wood from which these shav- 

 ings were planed weighed 12.37 grammes; and the 

 shavings, when thoroughly dried in the stove, weighed 

 7.5 grammes.* 



We hence conclude that a cubic inch of this wood, in 

 its original state, while the tree was still alive, contained 

 7.1531 grammes of ligneous parts which formed the 

 fabric of the wood, and 4.3369 grammes of sap, differ- 

 ing in its specific gravity little or nothing from common 

 water. 



* As the heat excited by the plane in taking off these shavings was sufficient to 

 evaporate a very sensible quantity of sap belonging to the wood from which they were 

 cut, the shavings became perceptibly dry during the operation ; for I found that forty 

 thin shavings sometimes lost more than one gramme (about of their weight) 

 in less than a minute. In order to obtain their true weight, whilst they still remained 

 part of the wood, I adopted the precaution of weighing the piece of wood both the 

 moment before and the moment after the operation of planing. The difference in 

 the weight of the wood, under these two circumstances, indicates the weight neces- 

 sary to be given to the shavings, and which is here always attributed to them. 



