FROM DIFFERENT APPATJA1 i ~ |* 



quantities of this coal in sheet iron cylinder stoves lined with 

 lire brick; and it is as well known, that an equally small 

 quantity of this coal cannot be consumed in an open grate. 

 The inference, therefore, which should be drawn from the 

 knowledge of these facts, is, that the open grate is an impro- 

 perly constructed apparatus to obtain the desired object, iml. - 

 pendent of the deleterious gas which it imparts to tin- room. 

 The question which then presents itself, is. whal arc the quali- 

 ties possessed by the former apparatus in which the latter 1- 

 deficient ? 



In the former, the coal is known to be completely sur- 

 rounded by a thick substance, which, when heated, retains ii 

 with great tenacity. The air admitted is in small quantity, 

 and, from the construction of the stove, it is necessarily consi- 

 derably elevated in its temperature, before it conns in contact 

 with the burning body. We infer from these tuts, tint 

 anthracite coal requires a very high temperature to produce 

 ignition, and. as we know that combustion cannot take |i! 

 without this prerequisite, the necessary means to effect it. are 

 consequently, indispensable. We also infer, that the commonlj 

 received opinion, that this coal requires a very large quantity 

 of air, or "strong draught,'' to cany mi its combustion, is ool 

 correct; the converse of tin's opinion being nearer true: ami 

 this may in part hi' demonstrated by an examination "i a single 

 piece of this coal which has been ignited. If we break the pi 

 of coal, the interior will presenl its original black colour ami 

 lustre, with the exception of an inconsiderable portion near th< 

 surface ; the body of the coal being sufficiently dense to exclude 

 the access of air. no combustion of iis interior can take plai 

 and, consequently, the quantity of air ni c< s e admitted 



to thi- coals, is nearly proportional to the quantity of coal con- 

 tained in their surface*, hut not in proportion to their positive 

 quantity, as would lie nearer the case, if this article were as 

 pervious to air as charcoal. Am excess of air, therefore, is 



injurious in proportion as the quantity exceeds that which can 



unite with whai is termed tin- combustible or base, inasmuch 

 is it tends to reduce its temp rature, and thereby renders it 



