The product of Edison's brain may be divided into three classes. The first embraces such arts and industries, or such apparatus, as have already been treated. The second includes devices like the tasimeter, phonomotor, odoroscope, etc., and others now to be noted. The third embraces a number of projected inventions, partially completed investigations, inventions in use but not patented, and a great many caveats filed in the Patent Office at various times during the last forty years for the purpose of protecting his ideas pending their contemplated realization in practice. These caveats served their purpose thoroughly in many instances, but there have remained a great variety of projects upon which no definite action was ever taken. One ought to add the contents of an unfinished piece of extraordinary fiction based wholly on new inventions and devices utterly unknown to mankind. Some day the novel may be finished, but Edison has no inclination to go back to it, and says he cannot under- stand how any man is able to make a speech or write a book, for he simply can't do it.