MANUAL OF TIDE OBSERVATIONS 



Tape Gauge 



~a 



elevation for the staff zero. At intervals along the support, metal 

 guides are arranged in pairs to hold the staff in a vertical position. 

 10. Multiple staff. — Along shore where shoal water extends some 

 distance offshore and 

 the range of tide is too 



large to be measured by 



a single staff, a succes- 

 sion of staffs may be 

 used. The different 

 staffs should be so grad- 

 ated and installed that 

 the graduations will be 

 continuous from one 

 staff to the next with 

 the readings on all of 

 the staffs referred to 

 the same zero. 





[- 



Reading MarH 



Floor of Tide House 



TAPE GAGE 



11. The tape gage 

 (fig. 2) is designed as a 

 substitute for the tide 

 staff in exposed locali- 

 ties where the water is 

 too rough for staff read- 

 ings. It is operated by 

 a float in a vertical box — 

 or pipe, known as a 

 ■float well, which serves 

 to dampen out the 

 larger wind waves. (See 

 pars. 65-72 for a dis- 

 cussion of float wells.) 

 Connected with the 

 float is a tape which 

 passes over a pulley in 

 the ceiling of the tide 

 house and is kept taut 

 by means of a counter- 

 poise. In general, it is 

 best to have the coun- 

 terpoise supported by a 

 movable pulley with 

 the^end of the tape at- 

 tached to the ceiling of 



the tide house in order to increase tlie limits of operation of the appa- 

 ratus. With a very small range of tide or a very high ceiling, how- 

 ever, the counterpoise may be attached directly to the free end of the 

 tape. 



12. 'There are several kinds of tape gages. In some, an index or 

 pointer attached to the tape moves over a fixed scale. In others, as 



Water Surface 



Figure 2. — Tape gage. 



