Of Chimney Fireplaces. 565 



If the doorway that is left in the back of the fireplace 

 for giving a passage to the chimney-sweeper, instead of 

 being closed with a tile, or with a flat piece of stone, set 

 in a groove made to receive it, according to the direc- 

 tions given in my Fourth Essay, be closed with a flat 

 piece of cast-iron, or of plate-iron, fixed at its lower 

 end, to the lower end of the doorway, by a hinge, or 

 movable on two gudgeons, this plate may easily be so 

 contrived as to serve occasionally as a register or door 

 for diminishing or closing the throat of the chimney. 



As this plate, situated at tht back part of the chimney, 

 could not produce any of those bad effects that have 

 with reason been attributed to the registers of common 

 register-stoves (which are placed on the breast of the 

 chimney), it appears to me to be very probable, that it 

 would be found useful as a register for occasionally 

 altering the size of the throat of the chimney, and regu- 

 lating its draught, as well as for occasionally closing up 

 that passage entirely. It would certainly be worth while 

 to try the experiment* 



Before I quit this subject, I must mention another 

 fault, which workmen employed in altering chimney fire- 

 places that are furnished with grates or stoves with 

 sloping backs are very apt to make. They leave the 

 back of the grate in its place, and instead of carrying up 

 the back of the fireplace perpendicularly from the bottom 

 of the grate, they first begin to carry it up perpendicu- 

 larly from the top of the iron plate that forms the back 

 of the grate ; and as this plate not only slopes back- 

 wards considerably, but rises several inches above the 



* Since the introduction of the cottage and gridiron grates, this contrivance has 

 come into very general use, and experience has shown it to be extremely useful. I 

 would strongly recommend it to those who fit up chimney fireplaces on these princi- 

 ples, never to omit this register ; it costs a mere trifle, and is very useful on many 



accounts. 



