The Observations made at _Paris_ by Monsieur _Payen_, assisted by several
_Astronomers_, as they were printed in _French_, and addressed to Monsieur
de _Montmor_, are these;
The _Eclipse_ began there, at 5 h. 44'. 52". _mane_. It ended at 7 h. 43'.
6". So that its _whole Duration_ was 1 h. 58'. 14". The _greatest
Obscuration_ they assign to have been 7. dig. 50. m. but they adde, that it
seem'd to have been greater by 3 minuts; which M. _Payen_ imputes to a
particular motion of _libration_ of the Suns Globe, which entertain'd that
Luminary in the same _Phasis_ for the space of 8. _min._ and some
_seconds_, as if it had been stopped in the midst of its Course; rather
than to a tremulous Motion of the _Atmosphere_, as _Scheiner_ would have
it.
They intimate that they took the time of each _Phasis_ from half _digit_ to
half _digit_, as well by a _Pendulum_, as by the _Altitudes_ of the _Suns
Center_ above the _Horizon_, corrected by the _Verticall Paralaxes_ and
_AEstivall Refractions_, by which they judged, that though the Time by the
_Pendulum_ may be sufficient for _Mechanicall_ Operations, yet 'tis not
exact enough for establishing the _Grounds of true Astronomy_.
They further conceive that the apparent _Diameters_ were almost equal;
seeing that in the _Phasis_ of 6. _Digits_, the _Circumference_ of the
_Moons disk_ passed through the _Center_ of that of the _Sun_, so as that
two Lines drawn through the two _Horns_ of the Sun, made with the _Common
Semi-diameter_ two _Equilateral Triangles_.
Next, they affirm, That there was so great a Variation in the _Parallaxes_,
by reason as well of the Refractions of the Air, which environs the Earth,
as of the Alteration of the Air, which encompasses the Moon, that the
_Horns_ of the Sun, there formed by the Shaddow of the Moon, appeared in
all kinds of _Figures_; Sometimes inclined to the _Vertical_, sometimes
_Perpendicular_ to the _Horizon_, and at last _Parallel_; the _Convexe_
part respecting the _Heaven_, and the _Concave_, the _Horizon_. By the
crossing (_so they go on_) of the {297} _Horns_ with the _Angles of
Inclination_, it will be easie to those, that have exactly observed them,
and that are skill'd in the higher _Astronomical_ Calculations, to compute
the _true Place_ of the _Moon_ in her _Orbite_, that so it may be compared
with that of the _Tables_, and with that, which has been observ'd in other
places, for the more precise determinating of the _Difference_ of
_Meridians_ (that being the way, esteem'd by _Kepler_ the most certain) and
for making a good Judgment of the defect or exactnesse of the Celestial
_Tables_.
Then they observe, That the _Beginning_ and the _Middle_ of this _Eclipse_
hapned to be in the _North Eastern Hemisphere_, and the _End_, in the
_South-Eastern_. The _first Contact_ (as 'twere) of the two Disks was
observ'd in the _Superior Limb_ of the _Suns Disk_ in respect to the
_Vertical Line_, and in the _Inferior_ in respect to the _Ecliptick_: But
the _Middle_, and the _End_ were seen in the _Superior Limb_, in respect
both to the _Vertical_ and the _Ecliptick_: And (what to this Author seems
extraordinary) both the _Beginning_ and the _End_ of this _Eclipse_ hapned
to be in the _Oriental_ part of the Suns Disk.
Lastly, they take notice, that by their Observations it appears, that there
is but little exactness in all the _Astronomical Tables_, predicting the
_Quantity_, _Beginning_ and _Duration_ of this Eclipse; Those of
_Lansbergius_ importing, That the Obscuration should be of 10. dig. 48';
those of _Ricciolo_, of 9. dig. 1'; and those of _Kepler_, of 7. dig. 30'.
16": Again, that the _Duration_ should be of 2h. 2'. Lastly, The
_Beginning_ did anticipate the _Ricciolan Tables_ by 5 _minuts_, the _End_
by 23; and the _Middle_, almost by 11. In the mean time the Author notes,
that the _Rudolphin Tables_ come nearest to the Truth; and withal assures
the _Reader_ of the goodnesse of the _Instruments_ employed in his
_Observations_, and of the singular care, he, together with his skilful
Assistants, took in making them.
* * * * *
_Some Inquiries and Directions concerning _Tides_, proposed by Dr.
_Wallis_, for the proving, or disproving of his lately publish't
_Discourse_ concerning them_.
The Inquisitive Dr. _Wallis_, having in his lately printed _Hypothesis_ of
Tides intimated, that he had reason to believe, that the _Annual
Spring-tides_ happen to be rather about the beginnings of _Febr._ and
_Nov._ than the two _AEquinoxes_, doth in a late Letter to the _Publisher_,
written from _Oxford_ in _Aug._ last, desire, that some understanding
Persons at _London_, or _Greenwich_, but rather nearer the Sea, or upon the
Sea-shore, would make _particular_ Observation of all the _Spring-Tides_
(_New-Moon_ and _Full-Moon_) between this and the End of _November_; and
take account of the _Hour_, and of the _Perpendicular height_: that we may
see, whether those in _September_, or those of _November_ be highest: And
it were not amiss, the Low waters were observed too. Which may be easily
done by a mark made upon any standing Post in the Water, by any {298}
Water-man, or other understanding Person, who dwells by the Water-side.
It would also deserve (thinks he) to be inquired into, whether, when the
Tides be highest, the Ebbs be ever lowest, & _contra_; (which is generally
affirmed, and almost put out of question) or rather (which sutes best with
this _Hypothesis_) whether, when the Tides are highest, both in the
_Annual_ and _Menstrual_ Periods, the Low waters be not also highest; and
at Neap Tides, the Ebbes also very low.
He adds, that he should expect, that the Spring Tides now coming, and those
at the beginning of _September_, should not be so high, as those at the
_middle_ of _September_; and then lower again at the _beginning_ of
_October_, and after that, higher at the _middle_ of _October_, and higher
yet about the _beginning_ of _November_ (at the usual times of
_Spring-tides_ after the _New_ and _Full_.)
* * * * *
_Considerations and Enquiries concerning _Tides_, by Sir _Robert Moray_;
likewise for a further search into Dr. _Wallis's_ newly publish't
_Hypothesis_._
In regard that the High and Low waters are observed to increase, and
decrease regularly at several seasons, according to the Moons age, so as,
about the _New_ and _Full Moon_, or within two or three daies after, in the
Western parts of _Europe_, the _Tides_ are at the _highest_, and about the
_Quarter-Moons_, at the _lowest_, (the former call'd _Spring-tides_, the
other _Neap-tides_;) and that according to the height and excesses of the
_Tides_, the _Ebbes_ in opposition are answerable to them, the heighest
Tide having the lowest Ebbe, and the lowest Ebbe, the highest Tide; the
Tides from the _Quarter_ to the _highest Spring-tide_ increasing in a
certain proportion; and from the _Spring tide_ to the _Quarter-tide_
decreasing in like proportion, as is supposed: And also the _Ebbes_ rising
and falling constantly after the same manner: It is wished, that it may be
inquired, in what proportion these Increases and Decreases, Risings and
Fallings happen to be in regard of one another?
And 'tis supposed, upon some Observations, made in fit places, by the
above-mentioned Gentleman, though, (as himself acknowledges) not thoroughly
and exactly performed, that the Increase of the Tides is made in the
_Proportion_ of _Sines_; the first Increase exceeding the lowest in a small
proportion; the next in a greater; the third greater than that; and so on
to the mid-most, whereof the excess is greatest, diminishing again from
that, to the highest Spring-Tide; so as the proportions, before and after
the _Middle_, do greatly answer one another, or seem to do so. And
likewise, from the _highest Spring-tide_, to the _lowest Neap-tide_, the
_Decreases_ seem to keep the like proportions; the _Ebbes_ rising and
falling in like manner and in like proportions. All which is supposed to
fall out, when no Wind or other Accident causes an alteration. {299}
And whereas 'tis observed, that upon the main Sea-shore the Current of the
Ebbings and Flowings is sometimes swifter, and sometimes slacker, than at
others, so as in the beginning of the Floud the Tide moves faster but in a
small degree, increasing its swiftness constantly till towards the _Middle_
of the Floud; and then decreasing in velocity again from the _Middle_ till
to the top of the High water; it is supposed, that in Equal spaces of Time,
the Increase and Decrease of velocity, and consequently the degrees of the
Risings and Fallings of the same, in Equal spaces of time, are performed
according to the _Proportion_ of _Sines_.
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.
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.
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 _Intrument_ to measure the Strength of the Winde.