Periodical Literature. 139 



A further investigation into the heat development and tempera- 

 tures in meilers leads to the following conclusions : 



1. In meilers the coaling process progresses in this manner: 

 As soon as by the direct firing the degree of heat is reached at 

 which the charring of the wood takes place, the charring pro- 

 gresses without a further outside source of heat. 



To start the charring a somewhat high initial temperature is 

 necessary, varying with species and size of billets from 315° to 

 420° C. As soon as the self charring process is begun the tem- 

 perature needs to be no more than 240° to 280° C in the coaling 

 zone ; hence 



2. Charring in meilers is a burning subdued by limited access 

 of air, which causes shrinking of the wood to the volume of coal 

 without any loss of substance usual with burning — an oxidation 

 without light effects, the German "schwelen" (smoulder). 



3. Small wood requires less heat than stout wood of the same 

 kind. 



4. The degree of heat which the wood under access of the 

 proper amount of air generates itself is the most advantageous 

 for the coaling process. 



5. Real burning, fire or glowing does not take place. Only to 

 initiate the process of charring is this required, and must not be 

 allowed to continue beyond the initiation. 



6. The descriptions in charcoal literature which refer to fire, 

 burning, glowing, and the statement that a glowing mass is to be 

 found in the meiler when burned out, are to be changed as not 

 describing actualities. 



A long and difficult series of experiments was made to deter- 

 mine the behavior of different qualities of wood, green, air-dry, 

 soaked, sour and partly rotten, etc., of beech, fir and spruce. 



1. The highest smouldering heat and the most rapid coaling is 

 developed in the rotten or doty wood. This also develops the 

 largest amount of gas and causes explosions readily. 



2. In green wood coaling proceeds slowly at first. But when 

 once begun it proceeds rapidly and shows a very high degree of 

 heat at the coaling zone due to the continued development of 

 steam. 



3. Wood which has been dry and then soaked (floated) at first 



