Page:Philosophical Transactions - Volume 001.djvu/313

 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 Cheeks, 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 Undulation, 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.

6. The State of the Weather, as to Rain, Hail, Mist, Haziness, &c. and the times of its Changes.

7. At the times of observation of the Tides, the height of the Thermometer; the height of the Baroscope; the height of the Hygroscope; the Age of the Moon, and her Azimuths; and her place in all respects; And lastly the Sun's place; all these to minutes.

And it would be convenient, to keep Journal Tables, for all these Observations, each answering to its day of the Month.

For the Apparatus of all these observations, there will be particularly necessary.

A good Pendulum-watch.

A Vane shewing Azimuths to minute parts.

An Instrument to measure the strength of the Winde.

A large and good needle shewing Azimuths to degrees. Rh