registers the rise and fall of the tide in the form of a graph. This 

 type of gauge is unattended except when it is necessary to correlate 

 the staff with the graph, reset the clock to the proper local time, and 

 change the paper roll. The nonregistering gauge is, in general, some 

 sort of pressure gauge, float, or staff, from which an attendant records 

 data periodically. 



B. EXISTING INSTRUMENTS 



1. Portable automatic tide gauge 



This instrument is in general use by this Office. The gauge 

 was designed especially for use at tide stations which are to be in 

 operation for only short periods of time. Ease of installation of 

 such instruments is a prerequisite. The float well is easy to install, 

 and the pipe to the float well serves as the support for the recording 

 device. The recording device consists of an eight-day clock that 

 drives a recorder drum. A spring-loaded recording stylus is operated 

 by the float. No elaborate housing is required for the recording 

 mechanism. The gear ratios of the recording stylus are variable to 

 accommodate a wide range of tides. The accuracy of this gauge is about 

 ±0.1 foot, and the price is approximately $660. 



2. Foxboro tide gauge 



Recent developments in the pressure-type gauges have greatly 

 increased the efficiency and accuracy of this type of gauge. Currently 

 none are in use by this Office, but they have been used with some 

 success by other agencies. One type, the Foxboro tide gauge, claims 

 an accuracy of ±1/4 foot and is priced at about $200. This instrument 

 is operated by the change of pressure caused by the change in water 

 level above a pressure plate. The pressure change is converted to a 

 pen deflection in a recorder, and the change in the level of the tide 

 appears as a graph. The advantages of this gauge are its ease of 

 installation and its capacity for transmitting measurements to one or 

 more receivers as far as 500 feet from the sensing element. It can be 

 used at any place where sufficient water is present to cover the ele- 

 ment. No permanent installation of any type is required. It would 

 appear that this type of instrument would prove useful in areas that 

 do not readily permit the use of the standard automatic portable tide 

 gage and/ or in instances where data are to be collected for brief 

 periods of time. It is also possible that the recording method may 

 facilitate the data handling. 



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