28 U. §. COAST AND GEODETIC SURVEY 
In the operation of the standard tide gage, the observer visits the station once a 
day and makes the appropriate notations by which the record can be related to the 
fixed tide staff which is part of the installation. The gage also requires a float well 
and a suitable shelter. A detailed description of the standard tide gage, together with 
instructions for installation and operation, is given in Coast and Geodetic Survey 
Special Publication No. 196, entitled ‘“‘Manual of Tide Observations.” 
Portable Tide Gage 
For use by hydrographic parties in the field, the Coast and Geodetic Survey has 
developed a portable automatic tide gage shown in Figure 12. This gage is 10 inches 
square on its base and with its weatherproof metal cover in place is 10 inches high. It 
was designed to provide a gage which can be easily installed in remote localities where 
wharves and docks are not available. 
The tide curve is made on cross section paper on a drum 7 inches long and 19.2 | 
inches in circumference. ‘This drum is geared to a clock movement within the drum so 
as to rotate once in 48 hours, giving a time coordinate of 0.4 inch to the hour. By the 
use of appropriate gear wheels, provision is made for five different height scales, allowing 
tides from less than 6 feet up to 25 feet to be recorded. In this gage, cross-section 
paper is used, so that the recording pencil is set to read the same as the tide staff. A 
detailed description of this gage, together with instructions for installation and opera- 
tion, will be found in the above-mentioned Special Publication No. 196. 
The Tide Record 
When the tide record consists of visual readings made on a tide staff, it is of advant- 
age in preparing it for tabulation, to plot these staff readings on cross-section paper to 
suitable time and height scales. Customarily the time is plotted along the horizontal 
axis and the height along the vertical axis.. A smooth curve is then drawn through the 
plotted points, from which the height of the tide at any time, or the times and heights 
of the high and low waters can be scaled. 
Plotting the staff readings on cross-section paper permits smoothing out accidental 
irregularities in the tide curve and the detection of errors. It also permits a more 
accurate determination of the times and heights of the high and low waters. 
A convenient form for plotting staff readings consists in plotting a number of 
successive days under each other on the same sheet. Quite apart from the economy in 
cross-section paper, this method brings out any departures from normal conditions and 
aids in the interpolation of breaks in the record. Figure 13 shows on a reduced scale 
the plottings of the tide curves at Boston for the first 6 days of July 1944 derived by 
plotting the hourly heights of the tide. The height scale is shown from 8 to 12 feet 
for the first tide curve, but for the others only the 8-foot line is marked. 
With automatic tide gages employing cross-section paper, as in the case of the 
portable gage, the recording pencil is set to give the height referred to a tide staff. 
Hence such a record is ready for tabulation as soon as taken off the gage. A comparison 
of the tide curve with the time and height notes made by the observer will indicate 
whether any time and height corrections are required. Generally no such corrections 
