178 GEOLOGY OF OHIO. 



in rear. The fire is maintained on grate bars similar to the furnace of a 

 steam boiler. 



There are many objections to this style of fireplace. 1. The 

 production of heat is too far away from the scene of its usefulness. 

 2. It is hard to clean the fires thoroughly. 3. The fire is not under 

 good control, as, on flat grate bars, the air is apt to burn through the fuel 

 in holes and thus allow the heat to be lowered without the burners' 

 knowledge. The radiation of the furnace is great and causes a loss of 

 fuel on this head. One very serious objection lies in the fact that the 

 outside furnace invariably causes heavy smoke during firing and for 

 sometime afterwards. This is due to the fact that when fresh coal is 

 thrown into a furnace full of incandescent coals, the evolution of gasses 

 is sudden and strong. These gases cannot get enough air in the furnace 

 for complete combustion and are "fixed" or "cracked" by the high heat 

 of the walls and brickwork around them. In this condition they go 

 into the kiln and though they meet plenty of free oxygen there to 

 burn them completely, the temperature is seldom high enough to cause 

 ignition. It is a general rule among fuel and combustion experts, that 

 "smoke once formed, remains smoke." The only way to prevent it, is 

 to cause complete combustion of the gases at the point of their formation, 

 and before they escape from contact With the incandescent objects around 

 them. 



The objections urged against the economy and success of the out- 

 side furnace, are of a sweeping character; indeed) but little can be said in 

 favor of this method of heat generation which does not apply with 

 greater force to every other kind of fireplace. 



Careful examination of the fireplace as seen in operation in many 

 points has demonstrated the essential truth of all of the theoretical con- 

 siderations advanced. 



2d. The inside furnace, is a fiat hearth, grate bar furnace similar 

 to the first described.except that it is buiit in the walls of the Vrl n and 

 foot of the bags, instead of the outside of the kiln. Its firedoor and ash- 

 door open flush with the outside of the kiln wall. The same faults as to 

 regulation control and ease of cleaning, can be urged against this 

 kind of fire. But as to loss by radiation, and opportunity of complete 

 combustion of gases, no fault can be found. The objections to this fire 

 are confined to points of ease and expediency in manipulation rather than 

 in radical defects of the combustion itself. 



3d. "The open front, incline grate bar fireplace," is perhaps the 

 commonest style in use. Without the bars the fireplace merely consists 

 of an opening into the kiln wall about eighteen or twenty inches wide, 

 three feet high and extending from the bagwall in the inside to six inches 

 •or a foot outside the line of the kiln's circumference. The grate bars are 

 hobked at the upper end over a cross bar near the top of the projecting 

 side walls of the fireplace and the bottom ends rest on the ground or over 

 a second cross bar lower down. In this fire the flames proceed directly 



