Of Chimney Fireplaces. \ 519 



diminish too much the opening of the doorway, and 

 will likewise be more liable to be torn away by the 

 chimney-sweeper in passing up and down the chimney. 



It will hardly be necessary for me to add, that the 

 tile, or flat stone, or wall of dry bricks, which is used 

 for closing up this doorway, must be of sufficient height 

 to reach quite up. to a level with the top of the walls 

 which form the new back and covings of the chimneys. 



I ought, perhaps, to apologize for having been so 

 very particular in these descriptions and explanations ; 

 but it must be remembered that this chapter is written 

 principally for the information of those who, having 

 had few opportunities of employing their attention in 

 abstruse philosophical researches, are not sufficiently 

 practised in these intricate investigations to seize, with 

 facility, new ideas, and consequently, that I have fre- 

 quently been obliged to labour to make myself under- 

 stood. 



I have only to express my wishes that my reader may 

 not be mvrt fatigued with this labour than I have been ; 

 for we shall then most certainly be satisfied with each 

 other. But to return once more to the charge. 



o 



There is one important circumstance respecting chim- 

 ney fireplaces destined for burning coals, which still 

 remains to be further examined ; and that is the grate. 



Although there are few grates that may not be used 

 in chimneys constructed or altered upon the principles 

 here recommended, yet they are not, by any means, all 

 equally well adapted for that purpose. Those whose 

 construction is the most simple, and which, of course, 

 are the cheapest, are beyond comparison the best, on all 

 accounts. Nothing being wanted in these chimneys but 

 merely a grate for containing the coals, and in which 



