5544 HYDROGRAPHIC MANUAL PaGE 518 



The angular rotation through which the contactors remain closed may be found 

 by first placing the gears in neutral so the disk can be turned by hand. The disk is 

 then turned slowly clockwise until the oscillator sounds and the red light flashes. The 

 position of the left edge of the slit relative to the depth scale should be accurately noted 

 when the red light flashes. Next, the disk is turned slowly counterclockwise until the 

 oscillator sounds and the red light flashes. Again the position of the left edge of the 

 slit relative to the depth scale should be accurately noted. The difference between 

 these two scale readings wfll be a measure of the length of signal. 



There is no adjustment of the index slit for the 600-fathom scale, such as is de- 

 scribed above for the 100-fathom scale. Neither is there any independent adjustment 

 of the dog for the 600-fathom scale, although a longer signal, equivalent to about 40 

 fathoms, is transmitted. Any adjustment of the dog for the 100-fathom scale also 

 affects the transmitted signal on the 600-fathom scale. So all depths read on this scale 

 must be corrected arithmetically. To determine the amount of the correction, a com- 

 parison of soundings read on this scale should be made with soundings read on the 100- 

 fathom scale in a manner similar to that described in 5542 for the Dorsey Fathometer 

 No. 3. Tlie comparison should be made in depths of about 200 fathoms where the 

 bottom is level and smooth. Each determination should consist of at least six com- 

 parisons and a number of determinations should be distributed throughout the time the 

 deep scale is used. The average difference between the soundings as read on the two 

 scales shall be applied arithmetically to all soundings read from the 600-fathom scale. 

 The results of each such determination shall be recorded in the Sounding Record. 



5544. Hughes Veslekari 



The Veslekari sounding instrument is usually operated simultaneously with the 

 Dorsey Fathometer No. 3, and it should be adjusted to agree with the Dorsey Fatho- 

 met'er after adjustment of the latter in accordance with 5542. Dm-ing periods in which 

 the Veslekari is being used, a simultaneous echo-sounding leadline comparison as 

 described in 5521, shall be made at least once a week, and in addition, at least three 

 daily depth comparisons shall be made between the two instruments. The vessel 

 need not be stopped for the latter, but the soundings should be reliable and preferably 

 in depths less than 100 fathoms and over smooth level bottom. At a "mark" at the 

 selected instant the soimding on the Dorsey Fathometer should be accurately read and 

 simultaneously a mark should be made on the fathogram of the Veslekari by pressing 

 the fix button. The depth registered on the Dorsey Fathometer should be entered 

 on the fathogram and identified as such. 



Before all comparisons the motor speed of the Veslekari should be verified in 

 accordance with 5555. 



For the weekly comparison, or if the Veslekari is used on a ship which does not 

 have a Dorsey Fathometer No. 3, the procedure should be as follows: With the motor 

 speed in adjustment (see 5555) a simultaneous echo-sounding leadline comparison 

 should be made in a depth of 15 to 30 fathoms in accordance with 5521. The phasing dial 

 should be set on zero position and the depth scale should be adjusted so that its zero is 

 at the left edge of the reference line recorded on the edge of the fathogram. The instru- 

 ment should then be adjusted so that the depth recorded on the fathogram, after cor- 

 rection for the velocity of sound and settlement and squat, will equal the measured 

 depth. The adjustment is made by stopping the instrument and then loosening the 

 nut that holds the keying cam, thus allowing the cam to be turned manually in the 



