In order to which, this following _Apparatus_ is proposed to be made use of. In some convenient place upon a Wall, Rock, or Bridge, &c. let there be an _Observatory_ standing, as neer as may be to the brink of the Sea, or upon some wall; and if it cannot be well placed just where the Low water is, there may be a Channel cut from the Low water to the bottom of the Wall, Rock, &c. The Observatory is to be raised above the High water 18. or 20. foot; and a Pump, of any reasonable dimension, placed perpendicularly by the Wall, reaching above the High water as high as conveniently may be. Upon the top of the Pump a Pulley is to be fastned, for letting down into the Pump a piece of floating wood, which, as the water comes in, may rise and fall with it. And because the rising and falling of the water amounts to 60. or 70. foot, the Counterpoise of the weight, that goes into the Pump, is to hang upon as many Pulleys, as may serve to make it rise & fall within the space, by which the height of the Pump exceeds the height of the Water. And because by {300} this means the Counterpoise will rise and fall slower; and consequently by less proportions, than the weight it self, the first Pulley may have upon it a Wheele or two, to turn _Indexes_ at any proportion required, so as to give the minute parts of the motion, and degrees of risings and fallings. All which is to be observed by _Pendulum-watches_, that have _Minutes_ and _Seconds_, with _Checks_, according to Mr. _Hugens's_ way. And because if the Hole, by which the water is let into the Pump, be as large as the Bore of the Pump it self, the weight that is raised by the water, will rise and fall with an Undulalation, according to the inequality of the Sea's Surface, 'twill therefore be fit, that the Hole, by which the water enters, be less than half as bigg as the Bore of the Pump; any inconvenience that may follow thereupon, as to the Periods and Stations of the Floud and Ebb, not being considerable. And to the end, that it may appear the better; what are the _particular_ Observations, desired to be made, near _Bristol_ or _Cheap-stow_ bridg, it was thought not amiss, to set them down distinctly by themselves. 1. The degrees of the Rising and Falling of the water every quarter of an hour (or as often as conveniently may be) from the Periods of the Tides and Ebbs; to be observed night and day, for 2 or 3 months. 2. The degrees of the velocity of the Motion of the Water every quarter of an hour for some whole Tides together; to be observed by a second _Pendul_-watch: and a logg fastened to a line of some 50 fathoms, wound about a wheel. 3. The exact measures of the Heights of every utmost High-water and Low-water, from one Spring-tide to another, for some Months or rather Years. 4. The exact Heights of Spring-tides and Spring-Ebbs for some Years together. 5. The Position of the Wind at every observation of the Tides; and the times of its Changes; and the degrees of its Strength.