The great science of bacteriology, dealing with these smallest of living things, only came into existence with the microscope, and it was a field which was not only wholly unknown and unexplored a few years ago, but there was no suggestion visible to the eye to direct attention to it, until the lens began to reveal the secrets of microcosm. What development the future may bring no one can predict, but to the biologist and the physician no more promising field exists. Certain it is that the knowledge already gained is of incalculable benefit, and constitutes one of the greatest eras of progress the world has known, for with the noble army of patient, devoted, and self-sacrificing physicians, the discoveries of the scientist, our boards of health, our hospitals and asylums for the insane, our quarantine laws, our modern plumbing and improved sanitation in the home and public departments, there is no reason why the life of man should not be extended far beyond the three-score and ten years, and the 50 per cent. of population dying in childhood saved for useful lives and citizenship. CHAPTER XXI. THE BICYCLE AND AUTOMOBILE. THE DRAISINE, 1816--MICHAUX’S BICYCLE, 1855--UNITED STATES PATENT TO LALLEMENT AND CARROL, 1866--TRANSITION FROM “VERTICAL FORK” AND “STAR” TO MODERN “SAFETY”--PNEUMATIC TIRE--AUTOMOBILE, THE PROTOTYPE OF THE LOCOMOTIVE--TREVITHICK’S STEAM ROAD CARRIAGE, 1801--THE LOCOMOBILE OF TO-DAY--GAS ENGINE AUTOMOBILES OF PINKUS, 1839; SELDEN, 1879; DURYEA, WINTON AND OTHERS--ELECTRIC AUTOMOBILES A DEVELOPMENT OF ELECTRIC LOCOMOTIVES AS EARLY AS 1836--GROUNELLE’S ELECTRIC AUTOMOBILE OF 1852--THE COLUMBIA, AND OTHER ELECTRIC CARRIAGES--STATISTICS. However superior to other animals man may be in point of intellect, it must be admitted that he is vastly inferior in his natural equipment for locomotion. Quadrupeds have twice as many legs, run faster, and stand more firmly. Birds have their two legs supplemented with wings that give a wonderfully increased speed in flight, and fish, with no legs at all, run races with the fastest steamers; but man has awkwardly toddled on two stilted supports since prehistoric time, and for the first year of his life is unable to walk at all. That he has felt his inferiority is clear, for his imagination has given wings to the angels, and has depicted Mercury, the messenger of the gods, with a similar equipment on his heels. We see the ambition for speed exemplified even in the baby, who crows in exhilaration at rapid movement, and in the boy when the ride on the flying horses, the glide on the ice, or the swift descent on the toboggan slide, brings a flash to his eye and a glow to his cheeks.