Inquiries relative to the Structure of Wood. 459 



A piece of this wood in a high state of preservation, 

 after it had been planed by the workman, was accurately 

 weighed, and then plunged into water, to ascertain its 

 specific gravity. It weighed 75.05 grammes, and dis- 

 placed no grammes of water, at the temperature of 

 61 F. ; its specific gravity, therefore, was 68,227, and a 

 cubic inch weighed 13.53 grammes. 



Forty shavings of the wood weighed 11.4 grammes, 

 which were reduced to 10.2 grammes when they had 

 been thoroughly dried in the stove. 



Hence we may conclude that a cubic inch of this old 

 wood was composed of 



Ligneous parts ..... 0.39794 cubic inch. 



Water . . . . . . 0.07186 



Air > 0.53020 



i.ooooo 



We may also conclude from these results, that the 

 wood of the centre of a large oaken post, though kept 

 for ages out of the reach of the rain, can never contain, 

 in our climate, less than 10 per cent of its weight in 

 water ; and that a cubic inch of such wood contains 

 more than half a cubic inch of air. 



The yearly medium temperature at Paris is about 54^ 

 F. ; now, as we have just seen that the habitual state of 

 dryness in woods at the temperature of 52 F. is such 

 as to give about n per cent of water for 100 parts of 

 wood, we must not be surprised at finding 10 per cent 

 of water in the interior of a large beam, 'after it had 

 been sheltered from the rain during 150 years. 



To ascertain whether the property of wood to attract 

 moisture from the atmosphere was augmented or dimin- 

 ished by the beginning of carbonization, I made the fol- 

 lowing experiments. 



