VI. VELOCITY. 95 



VI. MEASUREMENT OF VELOCITY. 

 A. LOGS AND CURRENT METERS. 



393. Patent Log, by Massey. For measuring speed at sea ; 

 in use in II. M. Navy. 



Hydrograpldc Department of the Admiralty. 



394. Patent Log, by Walker. For measuring speed at sea. 



Hydrograpldc Department of the Admiralty. 



394a. New Ship's Log. Benjamin Theophilus Moore* 



In this log a revolving cylinder, furnished with screw blades, is placed 

 behind a tube, the front portion of which terminates in a solid pointed head. 

 The cylinder turns upon a spindle, in bearings inside the tube. Within the 

 revolving cylinder is a water-tight tube of glass containing the recording 

 mechanism. This tube is drawn out for the purpose of reading the dials. 



The log line is attached near the centre of gravity of the whole instrument, 

 by which means the log is made to run horizontally, and below the surface of 

 the water, and as steadily as an arrow in the air. 



The mechanism, being entirely protected from contact with sea water, 

 works smoothly, and cannot get out of order. 



The glass tube is itself protected from any injury by the manner in which 

 it is contained within the revolving cylinder. 



This log will indicate any distance, from one-tenth of a cable to one 

 thousand miles, with great accuracy. 



394b. Massey's Patent Ship's Log. E. Massey. 



Massey's Patent Frictionless Sounding Log. 



E. Massey. 



394c. Massey's Frictionless Propeller Conical End 

 Log. E. Massey. 



394d. Massey's Patent Self-registering Ship's Logs. 



L. P. Casella. 



These logs are constructed on the rotating system devised by E. Massey, 

 and have registers and mile indices, to show distance run during the time the 

 log is overboard towing astern of ship. 



394e. Reynold's Patent Pendent Log. 



J. Cohen $ Co. 



This log is composed of two parts ; first, the rotating log itself, and second, 

 the apparatus for registering the distance run while the log is overboard. 



398. Ramsten's Patent Ship's Log. Elliott Brothers. 



396. Current Meter, for measuring the velocity of currents 

 in rivers at different depths. Elliott Brothers. 



An endless screw on a spindle turns two wheels at the same time, the one 

 recording every revolution of the blades by moving one division ; the other 

 indicating every complete revolution of the former. 



