Munday,October22. 1666.
Patternsof theTablesproposed to be made forObserving of Tides; promised in the next foregoingTransactions. OtherInquiriestouching the Sea. Some Considerations touching theParenchymousparts of the Body. Observables concerningPetrification. A Relation fromParis, of a kind ofWorms, that eat out Stones. Some promiscuous Observations made inSomersetshire. A Problem for finding the Year of theJulian Period, by a new and very easie Method. An Account of some Books, not long since publish'd, which are,1. Tentamina Physico-Theologica de Deo, AuthoreSamuele Parkero. 2. Honorati Fabri Tractatus duo; Prior, de Plantis et de Generatione Animalium; Posterior, de Homine. 3. Relation du Voyage de l'Evesque de Beryte, par la Turquie, la Perse, les Indes, &c. per Monsieur deBourges.
Patternsof theTablesproposed to be made forObserving of Tides; promised in the next foregoingTransactions. OtherInquiriestouching the Sea. Some Considerations touching theParenchymousparts of the Body. Observables concerningPetrification. A Relation fromParis, of a kind ofWorms, that eat out Stones. Some promiscuous Observations made inSomersetshire. A Problem for finding the Year of theJulian Period, by a new and very easie Method. An Account of some Books, not long since publish'd, which are,1. Tentamina Physico-Theologica de Deo, AuthoreSamuele Parkero. 2. Honorati Fabri Tractatus duo; Prior, de Plantis et de Generatione Animalium; Posterior, de Homine. 3. Relation du Voyage de l'Evesque de Beryte, par la Turquie, la Perse, les Indes, &c. per Monsieur deBourges.
In performance of what was promised in the last of thesePapersfor Observing theTides, here are subjoynedPatternsof theTablesthere mentioned;One, formarkingtheprecise Timeof the High waters and Low-waters during one Month; that is, betweenNewandNewMoon, orFullandFullMoon. Theother, for marking theDegreesof the Risings and Fallings of the Water inEqualspaces of Time, and theVelocityof its motion atseveralheights: TheDegreesofHeatandCold, &c.
TheTimes, assigned in thefirst, to the High waters and Lowest Ebbs, are taken out of Mr.Wing's Almanack, for this present year 1666, as he calculates them for the Month ofSeptemberforLondon Bridge. Only, whereas he takes notice but ofoneHigh-water for every day,Hereare setdown the Times of the other, and the two Ebbs intervening, by subdividing theDifferences, he assignes between two Tides, equally amongst them. In all which, though there may be Errors, that is not to be considered, seeing the Dissein is to Correct and State theTimesof theTides exactlybyExperiments, after this method. Mr.Wingstates the High waters to fall out atLondon-Bridgeconstantly, when the Moon is 46. deg. 30. min. to theWest-wardof theMeridian. For the Times, he marks for them, are made up by adding every day 3. hours, 6 minutes, to those in hisTablefor knowing the Time of the Moons coming to the South.
TheFirst Tableconsists oftwoParts, and each part offour Columns. Thefirstpart marks the Tides and Ebbs from the day of theNew-Moon to itsFull: Theother, from theFullto the nextNew. Thefirst Columnin both parts hath the day of the Month and Week;M.standing every where forMorningandA.forAfternoon. Thethirdcolumn hath theCharacterof the day of the Week prefixt to the Hour and Minute of the High-water, and answering to the day of the Month. ThelastColumn hath the same for the time of Low-water, varying theCharacterof the day, as often as the low-water falls out more early than the High-water. In thisExamplebetween the saidNewMoons there falls out in all just 57. periods of the Tide or Flowing water, and 58. of the Ebb or Low water; which numbers vary according to the Intervals of the Moons changes, but with what constancy and exactness, is to be inquired after: Which whosoever undertakes to do, may keep such aTable, as is here proposed, in a Book by it self.
TheotherTable doth in 9.Columnscomprehend the particular Observations of theDegreesof the Rising and falling of the Tides, and the other things specified at the Tops of them: ThefirstColumn marking the Hour and Minut common to all the several Observations. Each hour is divided in 3. equal Parts, that number of Observations being only pitch't upon by way ofExample: The numbers may else be varied at pleasure, when other more frequent Observations are thought fit to be made, or when they prove too frequent and laborious; though the most frequent are most desirable, till competent information of all particulars be attained.
TheRisingof the Tide from Low-water to the highest pitcht of the full Sea, is here supposed to be 60. foot: And the Degrees of its rising every 20. Minuts, to be in theProportionofSines,The whole time of Flowing supposed to be 6. hours. But thisExamplewill serve for marking theSpacesof the Increasing or Rising, as well as of the falling of the water, in order to the investigation of theirProportionsto one another, when theDurationof the Tide exceeds 6. hours by any number ofminuts, as well as for just 6. hours; seeing they may be easily collected from any Number of Observations; their precise Time and that of the Duration of the waters Rising and Falling (that is, the just interval between the High-Water and Low-water) being known: This Calculation bySines,being only set down as aConjecture, flowing from Observations of the Motion of the water in its Rising and Falling,which seems to observe this or some such like Proportion; which is supposed still to hold inallTides, be theDurationwhat it will; the Increase still continuing proportionably till the very midle of the Hight and Duration, and Decreasing afterwards in the same manner: Which whether it be so indeed or not, is that, which is desired to be known.
There is the like Proportion here supposed to be in thedifferent degreesof theVelocityof the Current of the Water afterEqualspaces of Times, as in its Rising and Falling: And so it is markt in theThirdColumn. But because thetrue Velocityof the Current of the Water, raised above the Levell456/1000of a foot, is unknown, it is by way of Supposition set at Ten feet in one Minute of an Hour, which being once stated, the rest distant from each other by the space of 20. Minutes of an Hour, are set down according to the sameProportionsofSinesbefore suggested. It being supposed, that of theVelocityof the Current of the Tide, after it hath flowed 20 minuts of an hour, be such, as a Log of Wood placed in the Water will move 10 foot in the space of one minute of time, at the middle of the Tide it will in the like space of Time move 114 f.276/1000, and so proportionably at other times: Which, howsoever these Proportions shall be found by Experiments to fall out, may be not unworthy of the pains and charges requisite to acquire the knowledge of it. For, besides the satisfaction it may afford upon other accounts, it may possibly be of no small use to those, who need an exact reckoning of their Ships running, when the Velocity of the Current of the Tide may be necessary to be known; lest through the defect of the knowledge of that, especially when it is reckoned less than indeed it is, the Ship be thrown in the night upon Shores, Rocks or Sands, when they reckon themselves to be far from them.
The Numbers in the 4, 5, 6, 7, and 8.Columnsare set down at random, only forExamplessake; there being no difficulty in the apprehension of it, and imitating of it in setting down the true Hights and Variations of theThermometer,Baroscope, &c. The Use whereof is so vulgarly known, that there needs no further Direction concerning them. But if any person who would make these Experiments, do not know the fabrick or use of any of the Instruments requisite for some of these Observations, nor where to have them, he may address himself to Mr.Shortgrave, one of theOperatorsof theRoyal Society, lodged inGresham Colledge, from whom he will receive full satisfaction about these things.
But the labour employed in the Observations of the Heat, Cold, &c. required to be taken notice of in order to the Ends proposed in the formerTract, and others that may be of no less delight than advantage, will be much retrenched, when Dr.Christopher Wrenputs in practice, what he some years ago proposed to theRoyal Societyconcerning anEnginewith aClockwork, which may perform these Observations in the last enumerateColumns, without being toucht or lookt after but once or twice a day.
The Tables themselves follow,
Fig. 1.