MANUAL OF TIDE OBSERVATIONS 43 



pencil holder and tighten a small screw which is then exposed to view 

 (par. 31), and then reassemble the removed parts. 



119. For the original setting of the recording pencil it is the aim 

 to make the adjustment so that as far as practicable extreme tides of 

 occasional occurrence will be recorded. For stations on the open 

 coast this adjustment will bring the curve of the normal tides in the 

 middle portion of the paper, but for stations on rivers the pencil 

 will be adjusted to bring the normal tide curve nearer the low- water 

 side of the paper to leave room above for recording the flood stages of 

 the river. After the original set-up of the instrument changes in 

 adjustment are in general to be avoided as they necessitate certain 

 allowances in the 



tabulations to pre- 

 serve a uniform 

 datum. When a 

 change of adjust- 

 ment is necessary 

 for any reason an 

 explanatory note 

 should be entered 

 in the record. 



120. Comparative 

 note. — ^W hen an 

 automatic tide gage 

 is originally in- 

 stalled, and daily 

 during its opera- 

 tion, a comparative 

 time and staff note 



must be entered on figure 19. — Tide curve and comparative note (standard gage). 



the tide roll with 



the corresponding point on the tide curve clearly indicated (fig. 19). 

 This is absolutely essential in order to obtain the correct time rela- 

 tions and to establish tidal datum planes. 



121. The comparative note must contain the date, the correct time 

 as obtained from a reliable source, the corresponding time as indicated 

 by the time clock of the tide gage, and the reading taken directly 

 from an outside tide staff or from a nonregistering float gage which 

 may have been installed as a substitute for the tide staff. A statement 

 relative to the wind and weather and the name or initials of the ob- 

 server making the note should be added. The exact point- of the tide 

 curve to which the note applies may be conveniently indicated by 

 first tilting the recording pencil to make a short horizontal line similar 

 to an hour mark and then drawing a tracer from the note to this line. 

 The point may also be indicated by a short vertical line made by 

 rocking the float drum, care being taken to hold the float wire so that 

 it will not spring off- the drum. 



122. A rubber stamp with suitable inscription is provided for 

 convenience in making the note. In entering the date it is desirable 

 to include the day of the week as a check on the day of the month. 

 Standard time should be used for the record consistently throughout 

 the year regardless of the fact that daylight saving time may have 

 been adopted temporarily for other purposes during certain months. 



