to quote a recently published circular, "are as worthless as the jewelry from a Christmas cracker." I have, I hope, clearly shown you the immense difference that exists between the imitation and the artificial ruby, taking an example; the former, it is true, depreciates rapidly in use and deserves such a description, but the latter has absolutely all the essential qualities of the natural stone, and to place the two on the same plane as worthless trash is unfair to modern. science and ingenuity. It must be clearly understood that there is no essential difference discernible between natural and artificial ruby as regards their beauty and their durability, which, as we have seen, are the two great items in the intrinsic value of a stone. But, of course, the price of a stone is chiefly determined by that third factor, which I have not so far taken into account-namely, rarity. Personally I must confess that I have never been able to see why one should value a thing for no other reason than that it is difficult to get, although I suppose here I am in a hopeless minority and that it is and always will be human nature to take this view. It would serve no useful purpose to enter into that fruitful subject of controversy, the price of an article due to extrinsic causes, but I may say this-that whilst to me personally one is as good as the other, if any man is prepared to pay £100 for a natural stone when he can obtain essentially the same thing, artificially produced, for £5, he is absolutely entitled to get it; and I would not wish you to think that I would defend for a moment the man who attempted to supply artificial as natural. But if this is so, it is still more the case that nobody has any right to supply anyone with paste under the name of artificial (or synthetic, or scientific, if these names are preferred) gem. I do think that the distinction between the two should be clearly recognized and that it should not be permitted to use the term artificial indiscriminately. At present this is being widely practiced; every day one sees offered for sale "rubies, emeralds, sapphires, and pearls artificially produced and having all the properties of the natural stone." Now, as I have indicated, such a thing as an artificial emerald answering this description is unknown and, as a matter of fact, the stones supplied under this title are, as a rule, nothing more nor less than paste imitations, the public being deliberately led to believe otherwise. There is in this case, as I have indicated, a real practical difference between the two articles, not merely a question of opinion. Again, one must deprecate the custom that has sprung up of arguing that, because "a rose by any other name will smell as sweet,' a "scientific" stone will be as good by any other name than its right When synthetic yellow sapphire is called "scientific topaz" perhaps no serious fraud is perpetrated, although it is misleading, but when artificial white sapphire is openly and deliberately sold at one. a fancy price as "synthetic diamond," with the support of the press, I for one consider that matters are going too far, and that this is being done at the present moment anyone can verify for himself. All these misrepresentations may bring wealth to individuals, but they tend to bring into disrepute the artificially produced stone, and instead of allowing it a place of its own as a distinct achievement, cause it to be looked upon as a spurious make-believe. However, I did not come here for the purpose of discussing this aspect, and I will not dwell upon it further. I have, as far as possible, given you a résumé of the whole subject and I will detain you no longer, except, if I may add one more word, to acknowledge the fact that my ability to bring this paper before you is very largely due to the assistance I have received in many quarters, and more particularly from Mr. E. Hopkins, whose enthusiasm on the subject of the technology of precious stones is only exceeded by his knowledge and experience. I am indebted to him, not only for much advice and information, but also for the loan of the specimens from which I have prepared the illustrations to this paper. THE STERILIZATION OF DRINKING WATER BY ULTRA VIOLET RADIATIONS.1 By DR. JULES COURMONT, Professor of Hygiene in the Faculty of Medicine of Lyon. That solar light is capable of killing bacteria has been recognized by Downes and Blunt, S. Arloing, Duclaux, and others. This action is due to the ultra-violet portion of sunlight, that is, to the waves of very small length, which are manifested by their chemical action rather than their power of producing heat. Solar light, however, is rather poor in ultra-violet rays, for they are to a great extent absorbed by our atmosphere. Indeed their very limited bactericidal power is scarcely comparable with the very great power possessed by the untra-violet radiation given out by some artificial light sources, notably by the mercury-vapor lamp, whose containing tube is made of quartz. Only such sources as the latter are of practical application to the sterilization of potable water. THE ULTRA-VIOLET RADIATION—THE QUARTZ MERCURY-VAPOR LAMP. A few general data will be first stated. The wave lengths (2) of light rays are generally measured in units which have received the designation of Ångströms (Å. units). The Ångström unit is equal to 0.0000000001 meter. The following table gives the wave lengths of a few different places in the spectrum: 1 Translated by permission from Revue générale des Sciences pures et appliquées, Paris, April 30, 1911, pp. 332-338. Ultra-violet radiations of solar origin of wave length smaller than 2.950Å. are absorbed by the atmosphere and do not reach us. Therefore in order to obtain light which is truly bactericidal (of wave length less than 2.800Å.) we must have recourse to artificial sources. The quartz mercury-vapor lamp is the most powerful among these latter. Luminescent mercury vapor is very rich in ultra-violet light. Its ultra-violet spectrum reaches from λ=3.650Å. toλ=2.225Å. Quartz is transparent to all light of greater wave length than 1.500Å., and therefore to all of the rays of the spectrum given out by luminous mercury vapor. Since the ultra-violet rays of smaller wave length than λ=2.800Å. are especially bactericidal, those between 2.800Å. and 2.225Å. render the quartz mercury-vapor lamp very nocuous to all living cells, dangerous to anyone handling it without precaution, as well as useful in the destruction of microbes. The quartz mercury-vapor lamp is fed by a continuous current. It must be protected by suitable cooling devices. With proper precautions theoretically it will last indefinitely, practically a very long time. The running of the lamp is very easily regulated either by a "sentinel" lamp in the same circuit with the mercury lamp or by simply noting the luminous state of the lamp itself. The lamp is most readily lit by rocking it. As soon as a small thread of mercury connects the two poles, a current of electricity is established and the lamp becomes luminous. The lamp is then turned to its usual position, the thread of mercury broken, but the current continues to pass by means of the luminous vapors from the mercury. THE STERILIZATION OF DRINKING WATER BY MEANS OF THE QUARTZ MERCURY-VAPOR LAMP. The most practical application of the bactericidal power of the ultra-violet radiation from the quartz mercury-vapor lamp is for the sterilization of drinking water. The difficulties met in the sterilization of drinking water are well known. Innumerable are the processes of filtration or of chemical or physical purification which have been advocated and applied. Some are of little value, others are effective but costly and requiring too extensive areas of land and too much manipulation. For a long while a method has been sought which is not only simple and economical, but also absolute in its efficacy for the sterilization of drinking water under such conditions as occur in the great majority of cases where water is collected for a city's use. Just such a simple, sure, and economical process has been devised by M. Nogier and myself. This process makes use of the bac 1 J. Courmont et Th. Nogier, Sur la stérilisation de l'eau potable au moyen de la lampe en quartz à vapeur de mercure. C. R. Acad. des. Sciences, 22 février 1909. tericidal properties of the ultra-violet rays from the quartz mercuryvapor lamp. * * * Let us state our method of procedure. At first we used the classical lamp of Kromayer. A metallic tube, provided with several test holes, and closed at one end by a quartz window (fig. 1), was placed face to face with a Kromayer lamp. The tube, filled with polluted water, was thus subjected to the radiation from the lamp for various lengths of time. Samples of the water were taken from each test hole by means of sterilized pipettes. Preliminary tests showed us that the water was very rapidly sterilized to about 0.30 meters from the lamp. Water was therefore permeable to the bactericidal rays from the lamp, and especially to those which killed very rapidly the microbes contained in the water. The most important fact for our purpose was therefore established. We next had constructed some long lamps (0.15 to 0.30 meters) of the form shown in figure 2. These lamps were hung in the axis of a metallic cylindrical box, about 1.20 meters in diameter, and holding 110 liters (fig. 2). This box could be filled through an orifice in the Quar FIG. 1.-Tube for determining to what distance water may be sterilized. top; a cock was provided at the bottom. Through a large glass window could be safely noted what happened within. The box was mounted on a pivot, so that it could be tilted for lighting the lamp. When we would experiment with thin layers of liquid, a glass basin could be introduced through the window and placed under the lamp. Finally, a single lamp was placed in the axis of a portion of a tube, 0.60 meter in diameter, so that the walls of the latter were nowhere farther than 0.30 meter from the luminous source. In fact, the distance could have been made much greater; we were convinced of that later. With this metal box we have made a great number of experiments, which enable us to affirm the rapid and complete sterilization of water, no matter how polluted, provided only that it be transparent. Later my collaborator, Th. Nogier, constructed a set of apparatus for the application of our discovery. The problem of the sterilization of potable water in private houses and in small public establishments (hotels, barracks, hospitals, etc.) |