S { 26 STRUCTURE OP WOOD, &C. 



Sap, &c. in found in one cubic inch of this wood, when the tree was alive.j 



of wood. J could have no greater bulk than 0*39353 cubic inch. 



As one cubic inch of water weighs 10/83 

 grammes, the 7'i63 grammes of sap, 

 found in the cubic inch of this wood, 



must have occupied a bulk equal to 036122 



Consequently, a cubic inch of the wood in 

 question, contained a quantity of air, 

 whose bulk was equal to 0' 24525 



Making together 1*00000 cubic inch. 



We Conclude from these results, that a young oak, in a grow- 

 ing state, at the beginning of September, when the wood 

 appears to be diffused with sap, contains, nevertheless, about a 

 fourth of its bulk of air, and that its solid ligneous parts do not 

 make quite 4-10ths 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, three Inches in diameter, measured 

 at two feet above the earth, was cut down on the 6th of Sep- 

 tember, whilst 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 5/*946 j consequently, a cubic inch of this 

 wood weighed 11 '49 grammes. 



From a piece of this wood, apparently fuJl of sap, 40 thin 

 shavings were taken, six inches in length, and half an inch 

 broad. The wood from which these shavings were planed, 

 weighed 12*37 grammes, and the shavings, when thoroughly 

 dried in the stove, weighed / 5 grammes*. 



• 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 percep- 

 tibly dry during the operation ; for I found that 40 thin shavings 

 sometimes lost more than one gramme (about l-12th of their weight} 

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

 they still remained patt 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 necessary 

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



them. 



We 



