70 M. Karsten's Observations and Experiments on 



ox3^gen does it require for its decomposition. On the other 

 hand, the faculty of burning diminishes in the same relation, 

 and coals of this description can only be burnt with the aid of a 

 strong current of air. On account of this inconvenience, and 

 also because a coal which is very poor in oxygen and hydrogen 

 gives little flame, the advantage of being able to develope much 

 heat is, as it were, annihilated in the coals with pulverulent coke, 

 having a large quantity of carbon in their composition. For this 

 reason, in all cases where calefaction is to be operated by means 

 of gases which burn, or, in other words, with flame, the coals 

 with pulverulent coke, having a great proportion of carbon in 

 their composition, must yield to the coals with conglutinated 

 coke, as well as to those with intumesced coke, having a large 

 proportion of carbon. 



On the other hand, those coals, with pulverulent coke, answer 

 best in cases in which the combustible is placed in immediate 

 contact with the body to be heated or melted, for example, in 

 the burning of lime and bricks, in the roasting of ores, and for 

 welding iron in a Jorge de mareclial^ mixed with coals furnish- 

 ing a very intumesced or vesicular coke, and having much 

 carbon in their composition : they would also do very well for 

 ordinary fires. Coals, with intumesced coke, or at least those 

 which swell and run in a high degree, do not answer well for 

 such purposes, when employed by themselves, because, from their 

 swelling too much in the grate, they prevent the access of the 

 air, or rather render the disengagement of the decomposed air 

 difficult, and thus oppose the activity of the draught. 



In cases where it is required to produce a very intense heat, 

 these coals would not answer, because they would give out a 

 lively melting heat, which, though strong enough while it last- 

 ed, would not keep up for any time. An excellent combus- 

 tible for this latter object is furnished by the coal with conglu- 

 tinated coke, whether it have much or little carbon in its com- 

 position ; but it answers still better for the use of a flame-fur- 

 nace, if it passes into coal with intumesced coke. 



For common house fires, for heating steam-engines, for the 

 service of brewhouses and distilleries, the coal with conglutinated 

 coke, having a large proportion of carbon, is that which answers 

 best, because a very strong melting heat is not required for such 



