AU ON THE L.OSS OF HEAT 



Although iron is a good conductor of heat, the plate suggested 

 would become sufficiently heated to maintain the necessary 

 temperature of the coal to carry on the combustion of the sur- 

 face exposed to it, with the exception of the points actually in 

 contact with it, which would be unimportant ; and this being 

 the case, its conducting power would, in other respects, be 

 obviously advantageous, and no danger of melting the iron, in 

 this situation, need be apprehended. If, however, danger from 

 melting or oxidation of the iron is feared, as a flat plate of iron 

 could not be permanently covered with any composition of clay, 

 it should be made circular, and defended at the top and bottom 

 by a flange projecting on the inside, the required thickness of 

 the clay. In addition to the plate suggested to cover the front 

 of the grate, a still further improvement might be made by 

 enclosing the ash pit also, both of w r hich might be done with 

 one plate of iron, and the grate for sustaining the coal might 

 rest upon cleats projecting from the interior, taking care to 

 give sufficient room for the expansion of the grate, to pre- 

 vent its being pressed outwards. A door for the removal of 

 ashes and the admission of air would be required, by which the 

 necessary quantity of air could be admitted without an ex- 

 cess. This construction would also be favourable for heating 

 the air which is to supply the combustible body, the advantage 

 of which must be obvious, when we reflect on the necessity of 

 cooling the burning body as little as possible. By the greater 

 expansion of the air, the quantity which comes in contact with 

 the burning body would be less in excess, at any one time, and 

 better adapted to attain the object ; the contact being more 

 frequent, from its increased velocity, the quantity actually united 

 in any given time, would probably be greater, and more heat 

 would consequently be produced. This construction, besides 

 the advantages already stated, would be more cleanly than the 

 open grate, would not require the blower, and could also be 

 made us-> of for culinary purposes, which is a very desirable 

 object to be attained. 



The construction of many grates is very objectionable, in an 

 important particular not yet noticed, which is. making the 



