152 Asiatic Society. (Marcu, 
The most useful Observations with reference to our general knowledge of the 
Tides are the following, beginning with those which are most easily made : 
1. The Observation of the Time of High water at a known place, on any day, 
and especially at new and full moon. 
2. The Observation of the Time of High water on several days in succession at 
the same place. 
3. The Observation of the Height of several successive Tides at the same place. 
4. Observations of the comparative Time of High water on the same day at 
‘different places in the same seas. 
1. An observation of the Time of High water at a given place on any known 
day may be useful. 
If the Time of the Moon’s southing on the same day be noted, this will facilitate 
the use of the observation, and will furnish an additional evidence of the correct- 
ness of the date. 
The Time of High water on the days of New and Full Moon is more particularly 
useful than on other days. 
Observations of the Time of High water may be made with sufficient accuracy 
without a tide-post. A place ought to be selected where the water is tolerably 
smooth. 
2. If there be opportunity at any place, it is desirable to observe the Time of 
High water every day for a fortnight. 
If it be ascertained that the two tides on the same day occur at regular intervals, 
one of them only need be observed. 
But there are often irregularities in the relative Times of the morning and even- 
ing Tide ; and these irregularities are different for different ages of the moon. In 
‘this case boih daily Tides should be observed. 
3. A single observation of the Height of the Tide is not of much value. But 
a Series of Heights for a fortnight is valuable, especially if accompanied with ob- 
servations of the times, 
The morning and evening Tide are often unequal, and this inequality sometimes 
varies considerably from one fortnight to another. 
In observations of the Height of the Tide, the difference of High and Low water 
ought to be taken. 
The channel of a river is not a good situation for such observations. 
4. The usefulness of tide observations will be greatly increased if those made at 
places in the same seas can be compared so as to shew the Rare at which the 
Tide wave TRAVELS: 
For example, the time which it employs in passing along a certain line of coast, 
or across a sea, or round an island, or up a bay. 
N. B.—The Tide wave is the elevation of the waters by which High water is pro- 
duced in many places at once. It is not observed as a visible wave, but is found by 
drawing a line upon the globe through all the places at which it is high water at a 
certain moment. The rate and direction of its travelling are known by comparing 
the position of such lines at successive times. 
N. B.—The Rare at which the Tide wave TRAVELS is quite distinct from the 
rate at which the stream of ebb or flow runs. 
N. B.—Also the Direcrion in which the Tide wave travels is quite distinct from 
the direction in which the tide ebds or flows. 
