and the Economy of Fuel. 89 



per, or the register in the ash-pit door, the fire-place 

 door be suddenly opened, it will frequently happen that 

 smoke, and sometimes flame, will rush out of the fire- 

 place by this passage. This accident may be easily and 

 effectually prevented, either by opening the damper, or 

 by closing the register of the ash-pit door, the moment 

 before the fire-place door is opened. This precaution 

 should be attended to in all fire-places of all dimensions, 

 constructed on the principles I have recommended. 



To economize the time and the patience of my reader 

 as far as it is possible, without suppressing any thing 

 essential relating to the subject under consideration, I 

 shall give him, in a very small compass, the general 

 results of a .set of experiments which cost me more 

 labour (or at least more time} than it would cost him to 

 read all the Essays I have ever written. I believe I am 

 sometimes too prolix for the taste of* the age ; but it 

 should be remembered that the subjects I have under- 

 taken to investigate are by no means indifferent to me ; 

 that I conceive them to be intimately connected with 

 the comforts and enjoyments of mankind ; and that 

 a habit of revolving them in my mind, and reflecting 

 on their extensive usefulness, has awakened my enthu- 

 siasm, and rendered it quite impossible for me to treat 

 them with cold indifference, however indifferent or tire- 

 some they may appear to those who have not been 

 accustomed to view them in the same light. 



I have already given an account, in all its various 

 details, of one experiment which was made (on the 

 1 5th of April, 1795) with the boiler we have just been 

 describing (see page 66). I shall now recapitulate the 

 general results of that experiment, and compare them 



