Some very simple devices for various oceanographical uses 1 75 



Woods of Messrs Kelvin & Hughes) an instrument which is in effect a rolling clino- 

 meter containing a compass which will always remain on an even keel. This also 

 will be contained in a perspex cylinder filled with gelatine only, and it too will have a 

 contained protractor permitting slopes to be read to one degree or so. Its compass 

 will be pivoted and not dependent upon buoyancy of a small float. This is an advant- 

 age because no depth limit will apply as it might if risk existed of a float being 

 compressed by water pressure to a state of nil buoyancy. When these devices have been 

 fully tested and made in sufficient number, the full scale net tests will be embarked 

 upon without delay and with confidence. Sight will not be lost of the need to ensure 

 that the compasses are held a sufficient distance from the warps to escape any dis- 

 turbing influence of the latter. 



So far we have discussed mainly the measurement of slopes of modest magnitudes 

 below the horizontal. We turn now to slopes measured as departures from the vertical. 



OFF-VERTICAL SLOPES: THE UNDERWATER COURSE OF DEEP-SEA WIRES 



AND CABLES 



Our first concern was to establish a means of checking the showings of the wire- 

 angle gauge to which earlier reference has been made above (Carruthers, 1954 b). 

 The need is to discover whether the pendulum gives a true value for the slope of a 

 hydro graphical wire (with its load of water bottles) when the observing ship is some- 

 what lively. It was decided to use jelly bottles to make an adequate series of tests. 



The first requisite was to devise a way of using them on the hydrowire without 

 interfering with the operation of water bottles and the wire-angle gauges at the same 

 time. The way chosen was to construct a simple " messenger-passer " easily attach- 

 able to the wire and able to carry a compass-containing jelly bottle held firmly parallel 

 to the latter. It would then only be necessary to fit the fall-away messenger hung 

 beneath such a device with an extra-long lanyard, to enable the two German clamp-on 

 jelly bottles (Fig. 3) to be used as well as the compass-containing jelly bottle. This 

 latter would be housed in a sort of little sentry box attached to the " messenger- 

 passer ". Such an arrangement would furnish three jelly slope values and one direction 

 reading for comparison with the readings of the wire-angle gauges under test. 



Illustrations of the simple instrument made by Mr. Woods to the writer's design 

 are presented (Fig. 6a and 6b). The first (6a) shows the situation before the arrival 

 of a messenger from above, i.e. with the fall-away messenger still hanging beneath. 

 The second (6b) shows the situation after the strike of the messenger from above, i.e. 

 with the fall-away messenger gone down to trip other instruments below. 



The device consists of a brass tube attachable by stretched rubber thongs to the 

 hydrowire. Running down its interior is a flat bar of brass with a small hinged piece 

 at its lower end. So long as this is bent upwards and contained in the tube, a 

 messenger can be hung from it, but as soon as the central bar is pushed down to full 

 extent the messenger must fall away. The central bar is bent over at the top as shown, 

 and is forked to receive the wire. A length of it near the top of the tube is slotted, and 

 through this slot a short length of thin glass rod can be passed and seated in a cupped 

 collar at the top of the tube. The glass rod takes the weight of the internal bar and the 

 hanging messenger when the device is cocked. The impact of a messenger from above 

 infallibly breaks^the glass rod and lets the pendant messenger fall away. 



The compass-containing jelly bottle is housed in the little fastened-on brass box 



