Let us pick up advertisement of (_A_) manufacturer, and select what appear to be the important statements which occur in it. We read: “The grate is slightly cone-shaped, which breaks up all clinkers and makes the fuel roll toward the wall of the fire-pot, where air is mixed with the gas. This generates a much greater degree of heat than it is possible to obtain with the old duplex and flat grates, and clinkers that would form and be wasted in other furnaces are thereby consumed.” From this the architect has learned to consider the question of the grate, and certainly he has definitely found out what is the disadvantage of the furnaces which use the old duplex or flat grates. It ought to be his aim to ask the manufacturer of furnaces using these types of grates what they have to say in defense of this indictment. But let us continue to read: “The ash-pit is large and roomy on the inside, and is provided with a very large door, which makes it convenient for the removal of ashes.” It is evident from this that there are furnaces on the market which have this defect of too small an ash-pit and door. The architect can then mentally pigeonhole this as a point to be considered in examining a furnace. Continuing our reading we come across this statement: “The (_A_) radiator is cast in one piece, with no joints to be cemented or bolted together.” This is evidently a reflection upon the weaknesses of other makes which have radiators that are bolted and cemented together, and on investigation we soon learn that furnaces often have leaky radiators which permit the coal-gas to escape into the warm air delivered through the house. Here is a definite defect to be remembered. Suppose we turn now to advertisement (_B_), and here we read the following: “Insulating air-chamber acts as a positive division between the bodies of warm and return air.” This is certainly a hint of a possible defect in a furnace. Perhaps not all of the furnaces are adequately insulated at this division between the bodies of returning cold air and the outgoing warm air, with the resulting loss of efficiency and sluggishness of circulation. Reading on in the same advertisement we find the following: “The (_B_) smoke-plate is an added precaution against the leakage of smoke and gas.” Evidently there is some possibility of smoke leaking into the warm air, or else this device would not have been suggested, and probably there are some furnaces where this is a very serious objection. Turning to the next advertisement, (_C_), we read: “Only the best grade of iron goes into the casting.” This is another consideration; for evidently, from the following, certain types of furnaces do not use the best castings, and give trouble. “Breakdowns and imperfections are reduced to a minimum. The endless series of treatments and repairs is never required.”