But 'tis withall conceived, that the said _Proportion_ cannot hold _exactly_ and _precisely_, in regard of the _Inequalities_, that fall out in the _Periods_ of the _Tides_, which are commonly observed and believed to follow certain _Positions_ of the _Moon_ in regard of the _Equinox_, which are known not to keep a _precise_ and _constant_ Course: so that, there not intervening equal portions of Time between one New Moon and another, the Moons return to the same _Meridian_, cannot be alwaies perform'd in the same Time; and consequently there must be a like Variation of the Tides in the Velocity, and in the Risings and Fallings of the Tides, as to equal spaces of time. And the Tides from New-moon to New-moon being not alwaies the same in number, as sometimes but 57, sometimes 58, and sometimes 59, (without any certain order of succession) is another evidence of the difficulty of reducing this to any great exactness. Yet, because 'tis worth while, to learn as much of it, as may be, the _Proposer_ and many others do desire, That Observations be constantly made of all these Particulars for some Months, and, if it may be, years together. And because such Observations will be the more easily and exactly made, where the Tides rise highest, it is presumed, that a fit _Apparatus_ being made for the purpose, they may be made about _Bristol_ or _Cheap-stow_, best of any places in _England_, because the Tides are said thereabout to rise to ten or twelve fathoms; as upon the coast of _Britanny_ in _France_, they do to thirteen and fourteen.