Short of this universal and complete appropriation of the electric light for signalling, however, it has been introduced with gratifying results in mercantile steamers for various important purposes—_e.g._, for lighting up the decks and surrounding wharfage during the work of loading or disembarking cargo; for projecting a flood of light ahead of a vessel’s course where navigation is difficult, and when danger in the shape of rocks or icebergs is imminent. The employment of the light in the way last named has been specially extended in the case of vessels intended for naval warfare. By its powerful aid the position and tactics of the enemy, the configuration of forts about to be assailed, or the nature of the land where it is proposed to disembark, can all be revealed, with a minuteness almost as perfect as that due to the light of day. Another feature on board ship affecting most intimately the well-being and comfort of passengers—too often, indeed, the safety of the ship itself—is that of ventilation. The thorough and efficient ventilation of ships is a feature which only during very recent times has received from shipowners and shipbuilders the amount of attention it deserves. The inadequacy of the methods of ventilation existing in emigrant ships, and as applied to holds for the ventilation of cargoes, engaged public attention very considerably a few years ago. The explosion on board the _Doterel_, with other like casualties, resulted in the appointment of a Royal Commission to inquire into the ventilation of ships. The prominence thus given to the subject and the experience then gained, have been fruitful of increased regard for efficiency in ship ventilation. In the absence for such a long time, however, of any system capable of universal application and having at once the merits of efficiency and cheapness, shipowners have adhered to old-fashioned, unscientific, and ineffective methods long after the invention of improved systems, one or other of which would have well repaid adoption. In ways and to an extent which may perhaps have been made evident in the previous pages, the introduction of the electric light is of itself greatly advantageous in this connection. One striking peculiarity of the change perhaps requires more explicit statement. This is the curious fact—patent enough to all who know anything of the properties of the incandescent light—that what is the very life of oil or other lights, is to it, certain death. The element thus vitally concerned is, of course, oxygen; and it need not be more than hinted that in existing so entirely without this element—at all times a great desideratum in passenger ships—the electric light is a vast benefactor to all who “go down to the sea in ships.”