1876.] On Currents and Temperature in the Ocean. 321 



filled by preference with oil, which terminates in the horizontal spiral 

 glass tube at a point which will vary with the total attractive influence 

 of the earth, and thus furnish a means of reading the instrument. The 

 electric contact arrangement described in the paper is thus rendered un- 

 necessary, and the reading of the instrument much simplified. 



II. " On Instruments for Recording the Direction and Velo- 

 city of Currents and the Temperature of the Water at 

 different Depths in the Ocean." By J. Rymer Jones, of 

 the Imperial Government Telegraphs, Japan. Communicated 

 by Prof. Rymer Jones, F.R.S. Received January 1, 1876. 



The object of these instruments is to register on board ship : — 



1st. The direction of currents which flow at different depths in 

 the ocean. 



2ndly. The velocity of those currents. 



3rdly. The temperature of the sea at all points between the sur- 

 face and bottom, without requiring the instruments to be hauled up 

 in order to register the results. 



The advantages of such results, if capable of being obtained, must 

 appear self-evident ; and the following description will, I hope, prove the 

 practicability of those methods which I propose to adopt in order to 

 arrive at the above desiderata. 



All three instruments are based on electrical principles. 



Diag. 1. fig. 1 represents a full-sized section of the instrument 

 employed for making serial observations of the direction of currents 

 flowing at different depths in the sea ; and in the lower part of the same 

 figure is shown the method for taking the temperatures at the same 

 points ; but as the description of this instrument will form a separate 

 paragraph, I shall dismiss it for the present with the remark that the 

 same leading-wires are used in connexion with both instruments. 



In considering the best method for registering the direction of deep- 

 sea currents, two things seem absolutely necessary : — 1st, some point 

 capable of taking up a fixed direction and uninfluenced by the currents ; 

 and 2ndly, a movable point taking up the direction of, and regulated by, 

 the current whose direction is required. With these data it appeared 

 sufficiently easy to arrive at the direction of the currents, by measuring 

 the angle between the fixed point and the movable point, which varies 

 with the direction of the current. It is clear that the only available 

 fixed point is that afforded by the unerring magnet, while the employ- 

 ment of a sufficiently large vane will cause the instrument to take up a 

 position in the direction of the current, the rest being only matter of 

 detail, which I now proceed to discuss. 



In order to keep the magnet in a perfectly horizontal position and un- 

 vol. xxiv. 2 B 



