SECT. 1J WATER SAMPLING AND THERMOMETERS 125 



the hinges. The weight of this bottle, with thermometer frame for three thermo- 

 meters, is 10 lb. It has a capacity of 1.14 1. 



Water-sampling bottles rigidly clamped to the wire, such as the Ekman or 

 Fjarlie types, are preferable in rough weather since there is less chance of 

 damaging the thermometers against the ship's side than with the free-swinging 

 Nansen- or Knudsen-type bottles. The weight of the water bottle is, however, a 

 very important factor. Much time can be saved on station, and many more 

 stations worked in a given time, if a considerable number of sampling bottles 

 can be attached in series on the wire at one time. Using 4-mm diameter wire 

 cord with a breaking load of 20 cwt, and a weight of 100 lb at the end, the safe 

 working load at 5000 m depth should never exceed 750 lb (approximately one- 

 third of the breaking load). With 5000 m of wire cord of 4 mm diameter the 

 weight will weigh, in water, approximately 630 lb, thus leaving only 120 lb for 

 the weight of the bottles. Ekman-type bottles, with the thermometers, weigh 

 in water 17-20 lb, depending on the country where they are made, Nansen 

 bottles weigh 7-8 lb and the Knudsen-type weigh 10 lb. Thus, in good condi- 

 tions, the maximum number of bottles which can be used on one deep cast is : 

 Ekman 6, Nansen 14, Knudsen 12 and Fjarlie 12. It cannot be too strongly 

 emphasized, however, that these are maximum numbers, only to be used when 

 weather conditions are very good. 



So far, all deep-sampling water bottles have been made entirely of metal — 

 usually brass — and so, as already explained, it is necessary to line the collecting 

 tube. A subsurface sampling bottle made almost entirely of plastic or other non- 

 metallic materials has, however, been designed by the National Institute of 

 Oceanography in Great Britain and should eliminate most of the problems of 

 maintenance and corrosion. Similar to the Fjarlie bottle in that only the 

 thermometer frame is reversed on closing, the N.I.O. sampling bottle is con- 

 structed mainly of polypropylene and has an improved type of seal for the 

 collecting tube which is free of all internal obstructions. The capacity of the 

 tube is 1.3 1. and the weight of the complete bottle in water is 3 lb. This will 

 allow the use of 20 to 25 bottles in series. In other words, in fine weather, the 

 normal range of samples required at a station in a depth of 5000 m could 

 be obtained in one cast. 



Large uncontaminated subsurface samples at all depths are becoming in- 

 creasingly needed for, among other things, the determination of trace elements, 

 and also in connection with work on the productivity of the oceans. Because of 

 the large quantities to be collected the sampler is usually of such a size that it 

 cannot be used in series and design varies largely with individual needs, the 

 only common factor being the necessity to have a non-metallic lining. For 

 instance, the large sampler used by the National Institute of Oceanography in 

 Great Britain for productivity work was adapted from a Nansen-Pettersson 

 water-sampling bottle, and holds 4 1. It is lined with nylon but provision is not 

 made for recording the temperature. On the other hand, a large sampler 

 constructed in 1937 for fisheries work in Canada had a capacity of 15 gallons 

 (ca. 68 1.). 



