Still another fact is brought to light by "Fire-pot - one piece, heavy-ribbed for purposes of increasing its radiating surface and to give it greater power of resistance against expansive force of the fire."

But here is something none of the other advertisements have told us: "Steel radiators are preferable for the use of hard coal; cast-iron radiators for soft or hard coal or wood." Also: "Radiators can be turned in either direction, thereby permitting smoke-pipe to be connected with chimney from the most advantageous point."

Finally, when we read in advertisement (E) the following, "Grate-bars are quickly removed and replaced. No bolts used," we wonder whether other furnaces use bolts, and whether there is a real objection to them.

Taking the information given in these advertisements, we can now make the following list of points to be considered in selecting any one make:

1. Is the grate so designed that clinkers will not form?

2. Are the grate-bars easily removable?

3. Is the ash-pit large and roomy and is the door amply large?

4. Is the radiator in one piece or so well fastened that it is gas-tight?

5. Is the radiator steel or a high grade of cast iron?

6. Is the inner casing so well insulated that it prevents premature heating of the descending air-currents?

7. What protection is there to prevent the chance passage of smoke into the warm air-chamber?

8. Is the outer casing properly insulated to prevent the waste of heat into the cellar?

9. Is the humidifier of ample capacity?

10. How is the fire-pot designed to increase the efficiency of its radiating surface and how is it strengthened against the expansive force of the fire?

11. Is there a long enough passage for fire-travel, so that no waste of heat is lost up the chimney?

12. Is the radiator flexible enough to permit of the connection of the smoke-pipe from the most advantageous point?

Most certainly this is an array of matters to be considered in the selection of a furnace which no one, except an expert, would think of, but they are all drawn from the advertisements, and this process of study is open to any one who is interested in learning the technical difficulties involved in the selection of this particular mechanical device. Perhaps not all of the knowledge gained is scientific, but at least there are stimulating bits of information that should be investigated.

Let us take one more example of this amusing game of comparing advertisements as applied to roofing materials. Here we will find many conflicting statements, but out of the whole battle of words we can glean some interesting truths.

Turn to advertisement (A) and we read the following: "Nearly every objection to wood shingles as a roof-covering is applicable to slates, which have still other adverse features. Slates are not fireproof. Ask the underwriter how the insurance companies regard them, and especially how, in comparison with clay tiles, they are not permanent, though more so than wood shingles. . . . Slates attract lightning, and while the sun warps shingles and the wind rips them off, slates are easily broken, and if there is even a slight settlement or vibration, repairs are necessary. Moisture gets under them, and during the winter months especially causes them to lift up and break off. When the ice thaws, the broken pieces slide out, leaving a defective place in the roof. This will happen every winter with a slate roof, and to keep such a roof in perfect condition it must be gone over each spring and the broken slates replaced with new ones."

Turning to advertisement (B) for asbestos shingles we read a different point of view: "Unfortunately, however, slate, particularly that which is obtainable on the market at present, does not last much longer than clay tile or tin shingles."

But reading from advertisement (C) we are amused at the following: "Slate being solid rock, they simply cannot wear out. They cannot rust, decay, crack, tear, warp, shrink, disintegrate, melt, burn, or smoulder. They will not contract or expand under the influence of heat or cold. They never need painting. They will not attract lightning - nor will they permit the growth of moss or decaying vegetable matter. . . . One of the most important advantages is from the insurance standpoint. Many roofs (not alone wooden shingles) are highly inflammable; but a slate roof will not ignite from sparks from fire in an adjacent building, from passing locomotives, or from any other cause. This fact is so well recognized that insurance companies allow a very substantial reduction in rates on slate-roofed buildings."

The contradictory statements here are very amusing, but the truth can be seen between the lines, that the makers of clay tile really believe that slate is their real rival, and have searched very hard to pick flaws in it as a material for roofing. And when the advertisement of the asbestos-shingle manufacturer is read, we learn that slate does not last much longer than clay tile. But both are insistent upon the opinion of the fire underwriters, and for this reason we naturally turn to see what they have to say, and we find that both slate and tile are under Class A roofing materials, with little difference made between them. As for the point of attracting lightning, why is slate used for switchboards if it is as good a conductor of electricity as a statement of the above type would imply? It is quite evident that one's opinion of slate after all this controversy will be about on a par with one's opinion of clay tile, and that one will realize that poor grades of either slate or tile, or poor workmanship, are rather more the causes of failure than the material itself.

Many more examples might be given of this interesting method of learning the truth from advertisements, but the principle in all cases remains the same, so that further quotations would only amuse rather than instruct.