the smallest object at the bottom was visible where the Sun, still high in the heavens, shone directly upon the surface.  But this purity would by no means satisfy the standard of Martial sanitary science.  In the first place, it is passed into a second division of the tank, where it is subjected to some violent electric action till every kind of organic germ it may contain is supposed to be completely destroyed.  It is then passed through several covered channels and mechanically or chemically cleansed from every kind of inorganic impurity, and finally oxygenated or aerated with air which has undergone a yet more elaborate purification.  At every stage in this process, a phial of water is taken out and examined in a dark chamber by means of a beam of light emanating from a powerful electric lamp and concentrated by a huge crystal lens.  If this beam detect any perceptible dust or matter capable of scattering the light, the water is pronounced impure and passed through further processes.  Only when the contents of the bottle remain absolutely dark, in the midst of an atmosphere whose floating dust renders the beam visible on either side, so that the phial, while perfectly transparent to the light, nevertheless interrupts the beam with a block of absolute darkness, is it considered fit for human consumption.  It is then distributed through pipes of concrete, into which no air can possibly enter, to cisterns equally, air-tight in every house.  The water in these is periodically examined by officers from the waterworks, who ascertain that it has contracted no impurity either in the course of its passage through hundreds of miles of piping or in the cisterns themselves.  The Martialists consider that to this careful purification of their water they owe in great measure their exemption from the epidemic diseases which were formerly not infrequent.  They maintain that all such diseases are caused by organic self-multiplying germs, and laugh to scorn the doctrine of spontaneous generation, either of disease, or of even such low organic life as can propagate it.  I suggested that the atmosphere itself must, if their theory were true, convey the microscopic seeds of disease even more freely and universally than the water.

“Doubtless,” replied our guide, “it would scatter them more widely; but it does not enable them to penetrate and germinate in the body half so easily as when conveyed by water.  You must be aware that the lining of the upper air-passages arrests most of the impurities contained in the inhaled air before it comes into contact with the blood in the lungs themselves.  Moreover, the extirpation of one disease after another, the careful isolation of all infectious cases, and the destruction of every article that could preserve or convey the poisonous germs, has in the course of ages enabled us utterly to destroy them.”

This did not seem to me consistent with the confession that disorders of one kind or another still not infrequently decimate their highly-bred domestic animals, however the human race itself may have been secured against contagion.  I did not, however, feel competent to argue the question with one who had evidently studied physiology much more deeply than myself; and had mastered the records of an experience infinitely longer, guided by knowledge far more accurate, than is possessed by the most accomplished of Terrestrial physiologists.