NARRATIVE OF THE CRUISE. 



117 



volume, being kept itself full of water. From the volume of the overflow as compared 

 with that of the bottle the depth at which it closed can be 

 readily calculated. 



The same principle has also been applied in the construc- 

 tion of a sounding machine for ascertaining the depth. A 

 straight brass tube A (fig. 43) is closed at the lower end by 

 a stop-cock B, and at the upper end by a nozzle C, to which 

 the india-rubber tube D is attached inside the tube A. 

 D is closed by a valve E, opening downwards. As this 

 instrument sinks, water enters through C, D, and E into the 

 brass tube A. When it begins to ascend, the water cannot 

 get back through the valve E, and in expanding it crushes 

 the tube D. On arrival at the surface, the excess of water is 

 tapped off through B, and the depth calculated, regard being 

 had to the temperature. 



A water-bottle of peculiar and ingenious construction, 

 used by Jacobsen in the German North Sea Expedition in 

 the " Pommerania "in 1872, 1 was supplied to the Challenger, 

 but was unfortunately mislaid at the fitting out, and notwith- 

 standing repeated searches was not found till the ship 

 returned. It is described by Dr. Jacobsen in the report of 

 the above voyage, and also in Liebig's Annalen for May 1873. 



Buchanan's Combined Sounding Tube and Water-Bottle. — Figs. 44, 

 45, 46, 47, represent a sounding tube with detaching weight, suitable 

 for ordinary sounding with wire. With it good samples of the mud 

 and of the bottom water are obtained without trouble. The instru- 

 ment consists of the "water bottle" A, a tube about 18 inches long 

 and 2\ inches in diameter, of about one litre capacity. It has at 

 each end a valve H, K, made of india-rubber, on a metal seating, 

 opening upwards. Above the upper valve H, the shank C is screwed 

 into the tube A, and below the lower one K, the mud tube B, which 

 is 12 inches long and 1 inch in diameter, is screwed to A. Into the 

 lower end of the mud tube B can be inserted the valve L, which consists 

 of a piece of thin sheet brass, cut out like a comb, and bent round into 

 a cylindrical shape. It is soldered to a stouter piece of brass tube, 

 which fits into the end of B and is retained by a bayonet-joint. At 

 the upper end of the shank C the tumbler D supports the weight E 

 by the sling F, and is in its turn supported by the sounding line M. 



The details of the tumbler are shown in figs. 45, 46, 47. It will be seen that at its upper end it 



1 Die Expedition zur physicaliscli-chemischen und biologischen Untersuchimg der Nordsee im Sommer 1872, 

 Berlin, 1875. 



44. — Buchanan's Combined Sound- 

 ing Tube and Water-Bottle. 



