U. S. COAST AND GEODETIC SURVEY 



TIDE STAFF 



5. The simplest kind of tide gage is a plain staff, which may consist 

 of a board 1 to 2 inches thick and 4 to 6 inches wide, graduated in 

 feet and tenths. The length should be sufficient to extend from the 

 lowest to the highest tide which may reasonably be expected in the 

 locality where the staff is to be used. Such a staff is secured in a 

 vertical position to a pile or other suitable support, with the gradua- 

 tions increasing upward. When nailed in 

 place or otherwise secured so as not to be easily 

 removable, it is called a fixed staff. 



6. Vitrified scale. — To overcome difficulties 

 resulting from the defacement of the gradua- 

 tions on a wooden tide staff, which may become 

 illegible after a comparatively short time, the 

 office has adopted a set of scales graduated in 

 feet and tenths, which are made by baking a 

 vitrified coating on wrought-iron strips. The 

 strips are in 3-foot sections about 214 inches 

 wide, the sections being so graduated that 

 when placed end to end form a single continu- 

 ous scale. The scales may be secured to a 

 wooden staff or suitable piece of timber, brass 

 screws and lead washers being provided for 

 the purpose. 



7. Glass tube. — For use in rough water a 

 glass tube about 1/2 inch in diameter is secured 

 to the face of the tide staff b}'^ spring clips or 

 other devices. The lower end of the tube is 

 partially closed by means of a notched cork 

 to dampen down the motion of the water inside. 



8. Portable staff. — After a fixed tide staff 

 has been in the water for a considerable period 

 of time, particularly in harbors where there 

 is much refuse or fuel oil^ the graduations may 

 become more or less illegible. To avoid this, 

 there are used at many of the tide stations a 

 portable tide staff (fig. 1) which may be easily 

 removed from the water and stored under 

 shelter when not in actual use. The tide staff 

 may be constructed in hinged sections for con- 

 venience in storing. In order that such a staff 

 shall always have its zero at the same elevation 

 when placed in the water for use, a tide staff 

 support permanently secured in place is 



^jjjg necessary. 



9. The tide staff support, with length cor- 

 responding approximately with that of the 



portable staff, may be constructed of 2-inch plank somewhat wider than 

 the tide staff and covered with copper sheathing as a protection against 

 teredos and other marine borers. A metal plate at the top of the sup- 

 port foims a shoulder on which a metal stop secured to the back of the 

 tide staff rests when the staff is in position for use, thus assuring a fixed 



Figure ■ 1.- — Portablo 

 staff and support 



