53 o Of Chimney Fireplaces. 



As all those who may be employed in altering chim- 

 neys may not perhaps know how to set off an angle of any 

 certain number of degrees, or may not have at hand the 

 instruments necessary for doing it, I shall here show 

 how an instrument may be made which will be found to 

 be very useful in laying out the work for the brick- 

 layers. 



Upon a board about 18 inches wide and 4 feet long, 

 or upon the floor or a table, draw three equal squares 

 (A, B, C, Fig. 12, Plate XIII.), of about 12 or 14 

 inches each side, placed in a straight line, and touching 

 each other. From the back corner c of the centre 

 square B draw a diagonal line across the square A, to its 

 outward front corner/, and the adjoining angle formed 

 by the lines d c and r /will be equal to 135 degrees, the 

 angle which the plane of the back of a chimney fire- 

 place ought to make with the plane of its covings. And 

 a bevel m n being made to this angle with thin slips of 

 hard wood, this little instrument will be found to be 

 very useful in marking out on the hearth, with chalk, 

 the plans of the walls which are to form the covings of 

 fireplaces. 



As chimneys which are apt to smoke will require the 

 covings to be placed less obliquely in respect to the 

 back than others which have not that defect, it would be 

 convenient to be provided with several bevels, three 

 or four, for instance, forming different angles. That 

 already described, which may be called No. i, will 

 measure the obliquity of the covings when the fireplace 

 can be made of the most perfect form ; another, No. 2, 

 may be made to a smaller angle, dee; and another, No. 

 3, for chimneys which are very apt to smoke, at the still 

 smaller angle d c /'. Or a bevel may be so contrived, by 



