Hkndehsox. — CoaJptl'h of Wes^t Xelsoii. 



301 



It is iiuportant to distinguisli between tlie effects of natural distillation 

 and atmospheric weathering. The folloAving table shows the progressive 

 effect of natural distillation : — 



Table A. 



Fixed 

 Carbon. 



Hydro- 

 carbons. 



Water. 



Ash. 



Locahty. 



Reference. 



It will be noted that the change from the brown coals to the best of 

 the sub-bituminous is accompanied by a diminution of the water and an 

 increase in both fixed carbon and hydrocarbons. Further change takes 

 the form of an increase of fixed carbon at the expense of the hydrocarbons, 

 the small percentage of water being decreased very slowly. With atmo- 

 spheric weathering, on the other hand, the percentage of water is increased ; 

 but the main change takes the form of a decrease in the hydrocarbons, 

 causing an apparent increase in the fixed-carbons percentage. A com- 

 parison of the odd numbers with the next following even numbers in Table B 

 will make this clear as far as sub-bituminous and bituminous coals are 

 concerned. 



Table B. 



A glance at Table C, on page 305, will show that the coals of west Nelson 

 have a very wide range of composition, and it is to this wide range in the 

 quahties of the various coals that the confusion of classification of the beds 

 in the past has been mainly due. 



