All these descriptions omit details that are essential to the comprehension of the reader. There is a great knack in twirling the vertical stick. It is taken between the palms of the outstretched hands, which are drawn backwards and forwards past each other almost to the finger tips, thus giving the drill a reciprocating motion. At the same time a strong downward pressure, is given which may be called a rotating pressure. The hands move down the drill; when they nearly reach the lower end they are brought back to the top with a quick, deft motion. This is repeated as rapidly as possible. If the lower part of the drill is observed when the motion begins it will be seen that powder is ground off and is collecting in the canal cut into the cavity from the side of the lower piece of wood. Soon, as the motion progresses, the powder begins to increase and to get darker, the odor of burning wood is noticed and the smoke is seen. Probably when the next motion ceases there will be a little curl of peculiarly colored smoke, which shows that active combustion has begun. The pellet of ground-off wood may now be shaken out of the slot or canal. At first it is dark; a thin line of smoke comes from it; gradually the fire spreads through it until it glows. In this semi-charred dust the heat is held until it increases to about 450°, or higher. Everything depends on keeping the dust in a heap; it is impossible to make fire without doing this. This is true in all kinds of wooden fire-making tools. By examination of many specimens of aboriginal fire apparatus it is found that both the drill and lower piece, which, for convenience, shall be called the hearth, must be of dry, inflammable wood. Wood that is soft from incipient decay is chosen; most often pieces riddled by worms. This is the _felicis materia_ spoken of by Festus as used by the Vestals. Wood of this kind is not only easier of ignition, but it is ground off more easily and retains the heat generated until enough is accumulated to ignite the powder. In strong, skillful hands fire can be made from wood that does not wholly fulfill these conditions. Woods vary in combustibility, depending on their density, coloring matter, and, perhaps, their chemical constitution. Sap wood of juniper and soft, white maple yield fire with the bow, but light mesquite is the best of all. The vascular, starchy flowering stems of plants have always been a favorite fire-generating material. It will be seen that the Eskimo attachments to the simple drill enable him to use wood ordinarily of no account for making fire. Sand is used by Indians and other peoples to increase the friction. From the material in the collection at the Museum, it is found that nearly every method that is or was used in the world is represented. The following classification, based upon the presumed order of development of the invention, is followed in this paper: