Dr. W. A. Miller on a Self-registering Thermometer. 395 



holds the governing masses in when their centrifugal forces exceed 

 the forces of the springs, and resists the motion hy forces of friction 

 increasing approximately in simple proportion to the excess of the 

 speed above that which just balances the forces of the springs. As 

 long as the escapement-tooth is unresisted, the nut collar is carried 

 round with the quicker motion of the outer tubular shaft, and so it 

 screws upivards, diminishing the force of the springs. Once every 

 semiperiod of the pendulum it is held back by either pallet, and the 

 nut collar screws down as much as it rose during the preceding inter- 

 val of freedom when the action is regular ; and the central or main 

 escapement-shaft turns in the same period as the tooth, being the 

 period of the pendulum. If through increase or diminution of 

 the driving-power, or diminution or increase of the coefficient of 

 friction between the governing masses and the ring on which they 

 press, the shaft tends to turn faster or slower, the nut collar works 

 its way down or up the screw, until the governor is again regulated, 

 and gives the same speed in the altered circumstances. It is easy 

 to arrange that a large amount of regulating power shall be implied 

 in a single turn of the nut collar relatively to the central shaft, and 

 yet that the periodic application and removal of about -^ of this 

 amount in the half period of the pendulum shall cause but a very 

 small periodic variation in the speed. The latter important condi- 

 tion is secured by the great moment of inertia of the governing masses 

 themselves round the main shaft. I hope, after a few months' trial, 

 to be able to present a satisfactory report of the performance of 

 the clock now completed according to the principles explained 

 above. As many of the details of execution may become modified 

 after practical trial, it is unnecessasy that I should describe them 

 minutely at present. Its general appearance, and the arrangement 

 of its characteristic parts, may be understood from the photograph 

 now laid before the Society. 



June 17. — Lieut. -General Sabine, President, in the Chair. 

 The following communication was read :— 



" Note upon a Self-registering Thermometer adapted to Deep-sea 

 Soundings." By W. A. Miller, M.D., Treas. and V.P.R.S. 



The Fellows of the Royal Society are already aware that the Ad- 

 miralty, at the request of the Council of the Society, have placed a 

 surveying-vessel at the disposal of Dr. Carpenter and his coadjutors 

 for some weeks during the present summer, to enable them to insti- 

 tute certain scientific inquiries in the North Sea. Among the objects 

 which the expedition has in view is the determination of deep-sea 

 temperatures. 



Now it is well known that self-registering thermometers of the 

 ordinary construction are liable to error when sunk to considerable 

 depths in water, in consequence of the diminution produced for the 

 time in the capacity of the bulb under the increased pressure to which 

 it is subjected. The index, from this cause, is carried forward beyond 



2D 2 



