Page 399 equipment and instruments 4671 



continued for long periods of time. The portable automatic tide gage is designed for 

 use at tide stations, which are to be continued for only short periods and where ease of 

 installation is an important factor. 



Special Publication No. 196 contains detailed information relative to the construc- 

 tion, and instructions for the installation and operation, of both types of automatic 

 tide gages. The requirements with respect to the installation and operation and the 

 submission of data shall be fully complied with. 



Any automatic tide gage should be visited and inspected frequently enough to 

 ensure continuous operation, especially during actual hydrography. The standard 

 automatic gage, once successfully installed, should give satisfactory results if the daily 

 comparison and inspection called for in Special Publication No. 196 are made. The 

 portable automatic gage should be visited at least every other day, if practicable, despite 

 the fact that it is driven by an 8-day clock and should operate normally without atten- 

 tion for a week. The possibility of long hiatuses in the record will be avoided by so 

 doing. The record should be changed every fourth day to preclude an erroneous inter- 

 pretation of a maze of curves. 



4671, Operation of Tide Gage 



Before installation and after operation, a tide gage should be thoroughly over- 

 hauled, cleaned, and oiled, with particular attention being paid to the pencil arm and 

 bearings. The pencil arm should also be cleaned periodically during operation, using 

 kerosene or unleaded gasoline for the purpose. 



All the difficulties which might arise cannot be anticipated. Those most commonly 

 encountered are listed in paragraphs 147 to 155 of Special Publication No. 196. It is 

 very important that the float well or pipe be vertical to keep the float from rubbing or 

 catching on its sides. The inside dimensions of the float well of a standard automatic 

 gage should be not less than 12 inches square. The diameter of the float is 8K inches 

 and a smaller float well will not provide enough clearance, especially if it is not exactly 

 vertical. 



4672. Tide Station Records 



The location of the tide station to be used for the reduction of soundings must be 

 entered in the Sounding Record in the appropriate space in rubber Stamp No. 38 at 

 the end of each day's work (see fig. 183). If more than one tide station is to be used 

 on the same day, the time when the change from one station to another is effective 

 shall be noted in the Record. Any height or time correction to be applied to the 

 tidal data to refer them to the locale of hydrography for use in reducing soundings shall 

 also be indicated in the Record. 



Field parties must scale the necessary hourly heights from the marigrams before 

 forwarding them to the Washington Office. Wlien the plane of reference is needed for 

 the reduction of soundings, it should be requested from the Office. (See also 1215 

 and 143.) 



The method of tabulating and reducing tide records is described in paragraphs 199 

 to 258, Special Publication No. 196, Manual of Tide Observations. Field parties will 

 ordinarily tabulate and reduce only those records needed for tide reducers for the 

 hydrography. 



