SCIENTIFIC EXCURSION OF THE CHALLENGER.

New Zealand Times, Volume XXIX, Issue 4136, 23 June 1874, Page 3

SCIENTIFIC EXCURSION OF THE CHALLENGER.

[Prom the Sydney Morn'mr/ Herald., Juno 24.] Yesterday morning Her Majesty's ship Challenger weighed anchor in Farm Cove, and proceeded to sea with a large party on board, chiefly consisting of gentlemen more or less interested in scientific pursuits and maritime affairs. Between thirty and forty excursionists availed themselves, on this occasion, of the hospitality of Captain Wares and his officers. The Challenger passed through the Heads at about a quarter-past nine o'clock, and on getting into deep water, away from the land, steered for a short distance due east, and then for a while E.S.E. The ship's head was then turned in a northerly direction towards Broken Bay, and when she was about three miles and a half from the land, soundings were taken in what was supposed to be forty fathoms—as proved to be the ease. Specimens of water were also brought up from the bottom, and from about half-way down, to test the relative temperature of the same. At this time—about a quarter-past eleven—the temperature on deck was 55 - Fahrenheit. The temperature of the surface of the water was 54'8 ; twentyfive fathoms below that it was 67', and at the bottom, in forty fathoms, it was 03 - . The Miller-Casella thermometer was used in this test of temperature. This appliance has been well explained in the October number of " Naval Science " last year. The invention is a very ingenious one. In the article referred to, Mr. Tizard, the chief navigating officer of the expedition, says : Tho thermometers used to ascertain tlio temperature of tho bottom, or any intermediate dentil, are selfadjusting maximum and minimum thermometers, constructed to resist tho pressure of the water. They are tho invention of tho lato Mr. Miller, F.K.S., and are made and tested by Mr. Casella, honce they are called " Miller-Casella thermometers." Each consists of a curved tubo, with a biUb at each cud; tho left bulb is filled with creosote, the expansion and contraction of which gives tho temperature. The creosoto acta on a small quantity of mercury in the part of tho tube, which moves up or down as the creosote expands or contracts. The tube is partially

filled with creosote ; ami, in addition, lias a small quantity of air in it—at the pressure of an atmosphere, to act as a buffer on the mercury in the tube, to keep it always in contact with the creosote in the bulb. In each part of the bulb, above the mercury, is an index shaped like a dumb-bell; the handle part of the dumb-bell being of steel ; and the index is retained in its place, when the mercury recedes from it by a hair attached to it, which, pressing against the glass tube of the thermometer, acts as a spring, the indices are set with a magnet. It is evident that the bulb of the thermometer would be exposed to the pressure of the water as well as to its temperature, and consequently the thermometer would register the temperature and the pressure. To eliminate the element of pressure, an additional is blown outside the bulb ; this bulb is partially iilled with spirit, which is boiled before it is hermetically closed, so that when closed it contains some spirit and some spirit vapour ; the pressure now acts on the outside bulb anil not on the inner, so that the inner bulb is only affected by temperature. These thermometers are tested in an hydraulic press at a pressure of from two to three tons on the square inch, and they have been found to answer admirably. On one occasion, when we sounded the great depth of 3.500 fathoms, they were broken from the enormous pressure of i\ tons on the square inch, and the maimer in which they were broken was rather extraordinary. The bulb was ftrst cracked slightly, either by the pressure or spontaneously, from imperfect annealing ; the water then forced its way through the crack into the thermometer, and pressure was, of course, brought to bear by that means on the inner part of the bulb, which being protected from an outward, and not from an inward pressure, smashed to atoms inside the bulb, which having the same pressure externally and internally, remained whole. The dredge apparatus was first thrown out from the port side in about forty fathoms, at the distance of about three and a-half miles from the coast near the Heads, and on the apparatus being drawn up little or nothing appeared to have been caught. Small as the " hard" was, however, it included specimens of the Nassa with the restless little hermit crab, one or two Polyzoa (aphrodite), a small bivalve shell—the " Venus roboralis," the pleurotoma, the marginella (an anelid), the Leda Dorni, and cardium. A second similar haul—a mile further off—secured specimens of the Turratella gunni (a not uncommon but very curiously shaped shellfish), several new crabs, a shell called the Voluta undulata, a Pccten bifrons—a shell to be found on the coast of South Australia—a Cassis, a Trigonia, several pretty pink starfish, a long and delicate brown tinted shell called " Myrtillus," Bryozoa, the Splneroma, a small sea urchin and the llanina. A new species of the rare crustacean called Scrolls was here also found in this " haul," and was carefully preserved. The long pink legs and small -body of the Stenorynelms here also put in an appearance. The next adventure was not made with the dredge, but with the trawl or large net, which was let clown when the ship was about six or seven miles off the land. What was brought up included five specimens of Gorgonia, a zoophyte (to the uninitiated) exactly resembling fern leaves ; an animal of the starfish kind—order, " Comatula," Antedon genus ■ —a very rare and beautiful object. The leaflike upper appendages of this animal were red and white, and the root-like shoots below were of a fine deep purple. The trawl also secured specimens of sponge, a curious zoophyte resembling a long sprig of heath primnoa, a fish like a " flathead," and a bright little scarlet fish, recognised by some of the party as a " jSTauigai." Again the trawl was let down, in thirtyfive fathoms, at twenty-five minutes to 2 p.m., the vessel then standing in towards the land, and the lighthouse bearing away to the northwest. The party now secured great numbers of specimens of the comatula adverted to, two or three gorgonia of different kinds (white and dark), and a very remarkable specimen of primnoa, &c. The officer in immediate charge of the dredging, &c, then sent down the dredge with the pendant swabs; but the apparatus broke off below. The Challenger was considerably to south-east of the Heads (off Bondi) at the last throw of the dredge at 4 o'clock; but from this also they got nothing. The vessel at length returned toward the mouth of the harbor, and finally readied a point near her former anchorage at 6 o'clock p.m.