210 



DISCOVERY REPORTS 



marking on a more extensive scale. It will be understood that the method cannot be 

 regarded as beyond the experimental stage until it has been demonstrated that the marks 

 are retained in the blubber for at least some months. 



HYDROLOGICAL INSTRUMENTS AND METHODS 

 Methods and apparatus in hydrology are more nearly standardized than those em- 

 ployed in biological work, and in consequence call for less detailed description. 



Apparatus for Bottom Sampling. The apparatus used for obtaining bottom samples 

 in routine work was supplied by the Admiralty. In shallow water, up to about 500 m., 

 the sinker shown in Fig. 30 was employed. This sinker is 28 lb. in weight and the upper 

 part is composed mainly of lead. At the 

 lower end is a short cylinder, of 2| in. 

 internal diameter, in which the bottom 

 sample is collected. This cylinder has a 

 pair of butterfly valves a at the lower end 

 to prevent the sample from washing out 

 during its passage to the surface, and a 

 series of holes b at its upper end to allow 

 the water to escape when it strikes the 

 bottom. 



In deep water greater weight is re- 

 quired, and with the very light wires used 

 in sounding it is not possible to haul the 

 weight back to the surface without risk 

 of breaking the wire or damaging the 

 sounding machine. The Baillie rod, 

 which was used for deep-water sound- 

 ings, is illustrated in Fig. 31 ; it is itself 

 only ID lb. in weight and is used in con- 

 junction with separate cast-iron sinkers 

 which are detached on striking the 

 bottom. The rod itself is hollow through- 

 out the greater part of its length ; it has 

 a pair of butterfly valves a at the lower 

 end to retain the bottom sample, and a 

 mushroom valve b at the upper end to allow the water to escape. The tube below the 

 mushroom valve can be unscrewed from the upper part, and when this has been done, 

 a long panel or shutter c can be removed, giving access to the bottom sample within. 

 The shaft d, which bears the eye for the attachment of the sounding wire, is free to 

 move vertically within the limits set by a cross-piece at its lower end, which engages 

 in slots e cut in either side of the casing. To the shaft is attached a small projection/. 



Fig. 30. 28 lb. sinker, 

 Admiralty pattern ; 

 sectional view. 



Fig.31. Baillie rod for deep-water 

 soundings: sectional view. For 

 explanation see text. 



