X. VETERINARY SCIENCE.--Historical Development of the Horseshoe.--By District Veterinarian ZIPPELIUS.--Very curious investigation of the development of the horseshoe.--22 illustrations. * * * * * THE PRODUCTION OF HYDROGEN AND OXYGEN THROUGH THE ELECTROLYSIS OF WATER. All attempts to prepare gaseous fluids industrially were premature as long as there were no means of carrying them under a sufficiently diminished volume. For a few years past, the trade has been delivering steel cylinders that permit of storing, without the least danger, a gas under a pressure of from 120 to 200 atmospheres. The problem of delivery without pipe laying having been sufficiently solved, that of the industrial production of gases could be confronted in its turn. Liquefied sulphurous acid, chloride of methyl, and carbonic acid have been successively delivered, to commerce. The carbonic acid is now being used right along in laboratories for the production of an intense coldness, through its expansion. Oxygen and nitrogen, prepared by chemical processes, soon followed, and now the industrial electrolysis of water is about to permit of the delivery, in the same manner, of very pure oxygen and hydrogen at a price within one's reach. Before describing the processes employed in this preparation, we must answer a question that many of our readers might be led to ask us, and that is, what can these gases be used for? We shall try to explain. A prime and important application of pure hydrogen is that of inflating balloons. Illuminating gas, which is usually employed for want of something better, is sensibly denser than hydrogen and possesses less ascensional force, whence the necessity of lightening the balloon or of increasing its volume. Such inconveniences become serious with dirigible balloons, whose surface, on the contrary, it is necessary to diminish as much as possible. When the increasing interest taken in aerostation at Paris was observed, an assured annual output of some hundreds of cubic meters of eras for the sole use of balloons was foreseen, the adoption of pure hydrogen being only a question of the net cost. Pure or slightly carbureted hydrogen is capable of being substituted to advantage for coal gas for heating or lighting. Such an application is doubtless somewhat premature, but we shall see that it has already got out of the domain of Utopia. Finally the oxyhydrogen blowpipe, which is indispensable for the treatment of very refractory metals, consumes large quantities of hydrogen and oxygen.