Steam-power is always very essential to deep-sea sounding. No trustworthy results can be obtained from a ship under sail; a perpendicular sounding is the one thing required, and, of course, with steam the vessel can be kept head to the wind, regulating her speed so that she remains nearly stationary. The sounding apparatus used needs some little description. A block was fixed to the main-yard, from which depended the “accumulator,” consisting of strong india-rubber bands, each three-fourths of an inch in diameter and three feet long, which ran through circular discs of wood at either end. These are capable of stretching seventeen feet, and their object is to prevent sudden strain on the lead-line from the inevitable jerks and motion of the vessel. The sounding-rod used for great depths is, with its weights,(26) so arranged that on touching bottom a spring releases a wire sling, and the weights slip off and are left there. These rods were only employed when the depths were considered to be over 1,500 fathoms; for less depths a long, conical lead weight was used, with a “butterfly valve,” or trap, at its basis for securing specimens from the ocean bed. There are several kinds of “slip” water-bottles for securing samples of sea-water (and marine objects of small size floating in it) at great depths. One of the most ingenious is a brass tube, two and a half feet in length, fitted with easily-working stop-cocks at each end, connected by means of a rod, on which is a movable float. As the bottle descends the stop-cocks must remain open, but as it is hauled up again the flat float receives the opposing pressure of the water above it, and, acting by means of the connecting-rod, shuts both cocks simultaneously, thus inclosing a specimen of the water at that particular depth. Self-registering thermometers were employed, sometimes attached at intervals of 100 fathoms to the sounding-line, so as to test the temperatures at various depths. For dredging, bags or nets from three to five feet in depth, and nine to fifteen inches in width, attached to iron frames, were employed, whilst at the bottom of the bags a number of “swabs,” similar to those used in cleaning decks, were attached, so as to sweep along the bottom, and bring up small specimens of animal life—coral, sponges, &c. These swabs were, however, always termed “hempen tangles”—so much does science dignify every object it touches! The dredges were afterwards set aside for the ordinary beam-trawls used in shallow water around our own coasts. Their open meshes allowed the mud and sand to filter through easily, and their adoption was a source of satisfaction to some of the officers who looked with horror on the state of their usually immaculate decks, when the dredges were emptied of their contents.