HEATING- POWER. 



103 



50-80 years old split beech 



120-160 

 100 

 120 

 70 

 100 

 100 

 100 

 120 



beech (stem) 

 birch (stem) . 

 oak (stem) . 

 larch (stem) . 

 elm (stem) . 

 spruce (stem) . 

 lime (stem) 

 silver-fir (stem) 



Sweet chestnut wood 



40 years old alder (stem) 



Black poplar aud aspen 



28 years old willow. 



40 ,, pyramidal poplar 



1-04 

 1-00 

 0-96 

 0-94 

 0-82 

 0-79 

 0-76 

 0-69 

 0-67 

 0-65 

 0-59 

 0-58 

 0-48 

 0-47 



The following results obtained by Brix show how many lbs. 

 of water at 0° C. may be converted into steam by burning 1 lb. 

 of each of the following woods : — 



Scotch pine (old trees) 



,, ,, (young trees) 



Alder . 

 Birch 



Oak .... 

 Beech 

 Hornbeam 



These figures show that the amount of woody substance in a 

 wood is the chief factor in determining its heating-power. 



The chemical way of deciding as to the heating-powers of 

 woods consists either in an elementary analysis of the wood, 

 and ascertaining how much oxygen is required for convert- 

 ing all the carbon and hydrogen it contains into carbon- 

 dioxide and water; or, this amount of oxygen may be deter- 

 mined by burning the wood in a closed retort with a metallic 

 oxide (red-lead), and ascertaining how much oxygen has thus 

 been used. 



A calculation of the average heating-power of different fire- 



