Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 169-177. 



Some very simple devices for various oceanographical uses 



By J. N. Carruthers 

 British National Institute of Oceanography 



Summary — An account is given of some very simple ways of determining the underwater courses of 

 suspension and towing lines in respect both of slope and direction. The means employed is to enclose 

 pendulums and compasses within suitable vessels containing hot gelatine solution. These are affixed 

 to the lines whilst the gelatine solution is hot. so that after the cooling which comes from immersion 

 in the sea, the pendulums and compasses become immovably fixed to give the necessary records. 

 It is shown that the devices could serve very usefully in studies of the pelagic trawl, and could be 

 adapted to determine the shape of trawling cables leading all the way down into the greatest ocean 

 depths. 



It will be of assistance if brief reference is made at the outset to two recently 

 published papers. In one of them (Carruthers, 195 4a, 181 et seq.) a preliminary 

 account was given of a simple current-measuring instrument designed for use by 

 commerical fishermen at echo-dictated depths. With that instrument, the speed and 

 heading of the water movement are given by the amount and direction of tilt imposed 

 by the current upon a cone made of non-magnetic mesh metal which is hung near its 

 apex in a smooth roller bearing carried in a sort of tuning-fork bracket. The latter 

 is borne on and can swing freely all round a rope strained between an anchor and a 

 buoy well below surface. To the latter is attached (for recovery) a long length of strong 

 thin line bent to a little marker buoy which serves as a finder — the whole system being 

 cast freely into the sea without any need for the investigating ship to anchor. The 

 bracket holds the cone well away from the line on which it is worked. 



Though, in the definitive model, the record for slope and direction is given by the 

 operation of a simple mechanism which locks a pendulum containing a compass 

 within itself, in an earlier model the record was got as follows: 



Rigidly fastened within the cone was a wide-necked bottle made of heat-resisting 

 glass filled half with gelatine solution and half with common kerosene. After a brief 

 sojourn of the bottle in the sea subsequent to its having first been stood in a bucket of 

 hot water, the gelatine solution solidifies beneath the kerosene — the slant of the firm 

 interface then formed being that imposed on the cone by the current. The slope is 

 easily measurable after recovery, and is of course convertible into a speed value on 

 reference to a calibration table. 



It was additionally useful to arrange for a small ring compass of aircraft type to 

 " float " at the interface of the two hot liquids. This was easily done by affixing a 

 diminutive buoy above the compass to the end that, when congelation took place, 

 the direction of the tilt was preserved. The arrangement can be appreciated from the 

 appropriate illustration which shows such a compass floating unrestrained between 

 the two hot liquids in a glass jug (Fig. 1). In use, the bottle is of course closed by 

 means of a cork or a screw-on metal cap made of aluminium or copper. 



In what follows attention will be paid to other uses of the simple device just 

 described which will be referred to for brevity and convenience as a "jelly bottle ". 



In the other paper (Carruthers, 1954 b) an account was given of a directional 



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