1876.] Currents and Temperature in the Ocean. 325 



vents the leakage of sea-water through the hole by which the wires enter 

 the top of the instrument ; and the compartment e C e is filled with 

 melted paraffin wax, which consolidates and effectually insulates the wires 

 and contacts from one another, should any moisture find its way in. 



The registering-instrument (diag. 2. fig. 3) is exceedingly simple and 

 greatly resembles the dial-plate of Breguet's electro -magnetic dial 

 instrument. 



Around the circumference of this dial-plate are sixteen brass contacts, 

 passing through an ebonite disk ; and to the under surface of each contact 

 is soldered one of the sixteen wires which form the core of the cable, 

 whose other ends are soldered to the upper surfaces of the contacts on 

 the disk (e e\ as before mentioned. 



Concentric with these metallic contacts are two circles, one on either 

 side. In the outer circle are the rhumbs and semi-rhumbs of the wind, 

 and in the inner circle are the degrees (Celsius) corresponding to those 

 marked in the diagram of the thermometer, this dial-plate being capable 

 of registering the results of both instruments. 



1 1 is a metallic lever capable of being moved round the dial by an 

 ebonite handle N, and the axis x of this lever is in connexion, through 

 the galvanometer g' g , with one pole of the battery C, the other pole Z 

 being put to earth, E'. 



In the centre of each brass contact is an indentation for dropping the 

 lever into ; and when not in use the handle can be turned back on to itself, 

 by means of a hinge (n n) in the centre, and thus break the circuit. 



The different parts of the instrument having now been explained, J 

 shall proceed to describe the manner in which it is intended to take an 

 observation. 



After attaching weights sufficiently heavy to carry the instrument 

 steadily down in an upright position to the detaching-instrument (diag. 

 1. fig. 3), paying out is commenced ; and under the influence of the 

 vane E, the instrument takes up a position in the direction of the cur- 

 rent, varying in direction as the currents vary. Whenever it is desired 

 to take a reading, the lowering is stopped, and the instrument in mid 

 ocean will be pointing in the direction of the current, while the magnet 

 (mm) is pointing steadily to the north. 



Tn order to understand the arrangement of the sixteen leading wires, 

 let us suppose the instrument to be influenced by a current from the 

 north; the direction then of the vane and magnet will coincide (diag. 2. 

 fig. 1), and the platinum contact pp (diag. 1. fig. 1), attached to the cop- 

 per wire w w, and which is always at right angles to the magnet m m, 

 will be rubbing against the under surface of the contact pointing due 

 west (W.). If, then, one of the sixteen wires in connexion with the 

 upper surface of this contact be soldered to the under surface of the 

 contact on the registering dial-plate marked N (diag. IT. fig. 3), when 

 lever 1 1 is moved slowly over this contact, on the upper surface of the 



