they put into Crucibles made of Earth, five foot long, square and
Pyramid-wise. The Entry is near a foot square. These Crucibles are laid
sloaping, eight undermost, and seven above them, as it were betwixt them,
that the Fire may come at them all, each having its particular Furnace or
Oven. The _Brimstone_ being dissolved by the violence of the heat, drops
out at the small end of the Crucible, and falls into a Leaden-Trough or
Receptacle, common to all the said Crucibles, through which there runs a
continual Rivolet of cold water, conveyed thither by Pipes for the cooling
of the dissolved Sulphur, which is ordinarily four hours in melting. This
done, the Ashes are drawn out by a crooked Iron, and being put into an Iron
Wheel barrow, are carried out of the Hutt, and {46} being laid in a heap,
are covered with other exiled or drained Ashes, the better to keep them
warm; which is reiterated, as long as they make _Brimstone_.
To make _Coperas_ or _Vitriol_, they take a quantity of the said Ashes, and
throwing them into a square planked pit in the Earth, some four foot deep,
and eight foot square, they cover the same with ordinary water, and let it
lye twenty four hours, or until an Egg will swim upon the liquor, which is
a sign, that it is strong enough. When they will boyl this, they let it run
through Pipes into the Kettles, adding to it half as much Mother-water,
which is that water, that remains after boyling of the hardned _Coperas_.
The Kettles are made of Lead, 41/2 foot high, 6 foot long, and 3 foot broad,
standing upon thick Iron Barrs or Grates. In these the Liquor is boyled
with a strong Coal-fire, twenty four hours or more, according to the
strength or weakness of the Lee or Water. When it is come to a just
consistence, the fire is taken away, and the boyled liquor suffered to cool
somewhat, and then it is tapp'd out of the said Kettles, through holes
beneath in the sides of them, and conveyed through wooden Conduits into
several Receptacles, three foot deep and four foot long (made and ranged
not unlike our Tan-pits) where it remains fourteen or fifteen dayes, or so
long till the _Coperas_ separate it self from the water, and becomes icy
and hard. The remaining water is the above-mentioned Mother-water; and the
elixed or drained Ashes are the Dregs, or _Caput mortuum_, which the Lee,
whereof the _Vitriol_ is made, leaves behind it in the planked Pits.
* * * * *
_A further Account of Mr. _Boyle_'s Experimental _History_ of _Cold_._
In the first Papers of these _Philosophical Transactions_, some promise was
made of a _fuller_ account, to be given by the next, of the _Experimental
History of Cold_, composed by the Honourable Mr. _Robert Boyle_; it being
then supposed, that this _History_ would have been altogether printed off
at the time of publishing the {47} _Second_ Papers of these _Transactions_;
but the Press, employed upon this Treatise, having been retarded somewhat
longer than was ghessed, the said promise could not be performed before
this time: wherein it now concerns the inquiring World to take notice, that
this subject, as it hath hitherto bin almost totally neglected, so it is
now, by this Excellent Author, in such a manner handled, and improved by
near _Two hundred_ choice _Experiments_ and _Observations_, that certainly
the _Curious_ and _Intelligent_ Reader will in the perusal thereof find
cause to admire both the Fertility of a Subject, seemingly so barren, and
the Author's Abilities of improving the same to so high a Degree.
But to take a short view of some of the particulars of this _History_, and
thereby to give occasion to _Philosophical_ men, to take this Subject more
into their consideration, than hitherto hath been done; the Ingenious
Readers will here see,
1, That not only all sorts of _Acid_ and _Alcalizate_ Salts, and Spirits,
even Spirit of Wine, but also Sugar, and Sugar of Lead mixed with Snow, are
capable of freezing other Bodies, and upon what account they are so.
2, That among the Substances capable of being frozen, there are not only
all gross sorts of Saline Bodies, but such also as are freed from their
grosser parts, not excepting Spirit of Urine, the _Lixivium_ of Pot-ashes,
nor Oyl of Tartar, _per deliquium_, it self.
3, That many very spiritous liquors, freed from their aqueous parts, cannot
be brought to freeze, neither naturally, nor artificially: And here is
occasionally mentioned a way of keeping _Moats_ unpassable in very cold
Countries, recorded by _Olaus Magnus_.
4, What are the ways proper to estimate the greater or lesser Coldness of
Bodies; and by what means we can measure the intensness of Cold produced by
Art, beyond that, which Nature needs to employ for the freezing of Water;
as also, in what proportion water of a moderate degree of Coldness will
{48} be made to _shrink_ by Snow and Salt, before it begin by Congelation
to _expand_ it self; and then, how to measure by the differing Weight and
Density of the same portion of Water, what change was produced in it,
betwixt the hottest time of Summer, and first glaciating degree of Cold,
and then the highest, which our Author could produce by _Art_: Where an
Inquiry is annex'd, whether the making of these kind of Tryals with the
waters of the particular Rivers and Seas, men are to sail on, may afford
any useful estimate, whether or not, and how much, ships may on those
waters be safely loaden more in Winter, than in Summer. To which is added
the way of making exact Discoveries of the differing degrees of Coldness in
differing Regions, by such Thermometers, as are not subject to the
alterations of the _Atmosphere's_ gravitation, nor to be frozen.
5. Whether, in Cold, the diffusion from Cold Bodies be made more strongly
downwards, contrary to that of Hot Bodies: Where is delivered a way of
freezing Liquors without danger of breaking the Vessel, by making them
begin to freeze at the bottom, not the top.
6. Whether that Tradition be true, that if frozen Apples or Eggs be thaw'd
neer the Fire, they will be thereby spoil'd, but if immersed in cold water,
the Internal Cold will be drawn out, as is supposed, by the External Cold;
and the frozen Bodies will be harmlesly thawed? _Item_, Whether Iron, or
other Metals, Glass, Stone, Cheese, &c. expos'd to the freezing Air, or
kept in Snow, or Salt, upon the immersing them in Water will produce any
Ice? _Item_, What use may be made of what happens in the different waies of
thawing Eggs and Apples, by applying the Observation to other Bodies, and
even to Men, dangerously nipp'd by excessive Cold. Where is added not only
a memorable Relation, how the whole Body of a Man was succesfully thawed
and cased all over with Ice, by being handled, as frozen Eggs and Apples
are; but also the Luciferousness of such Experiments, as these: and
likewise, what the effects of Cold may be, as to the Conservation or
Destruction of the Textures of Bodies: and in particular, how Meat and
Drink {49} may be kept good, in very Cold Countries, by keeping it under
Water, without glaciation? as also, how in extreme Cold Countries, the
Bodies of Dead Men and other Animals may be preserved very many years
entire and unputrified? And yet, how such Bodies, when unfrozen, will
appear quite vitiated by the excessive Cold? Where it is further inquired
into, whether some Plants, and other Medicinal things, that have specifique
Vertues, will loose them by being throughly congealed and (several wayes)
thawed? And also, whether frozen and thawed Harts-horn will yield the same
quantity and strength of Salt and saline Spirit, as when unfrozen? _Item_,
Whether the _Electrical_ faculty of _Amber_, and the _Attractive_ or
_Directive_ Virtue of _Loadstones_ will be either impaired, or any wayes
altered by intense Cold? This Head is concluded by some considerable
remarks touching the operation of Cold upon Bones, Steel, Brass, Wood,
Bricks.
7, What Bodies are expanded by being frozen, and how that expansion is
evinced? And whether it is caused by the intrusion of Air? As also,
whether, what is contained in icy bubbles, is true and Springy Air, or not.
8, What Bodies they are, that are contracted by Cold; and how that
Contraction is evinced? Where 'tis inquired, whether _Chymical Oyles_ will,
by Congelation, be like expressed Oyls, contracted, or, like aqueous
Liquors, expanded?
9, What are the wayes of _Measuring_ the _Quantity_ of the Expansion and
Contraction of Liquors by Cold? And how the Author's account of this matter
agrees with what Navigators into cold Climats, mention from experience,
touching pieces of Ice as high as the Masts of their Ships, and yet the
Depth of these pieces seems not at all answerable to what it may be
supposed to be.
10, How strong the Expansion of freezing water is? Where are enumerated the
several sorts of Vessels, which being filled {50} with water, and exposed
to the cold Air, do burst; and where also the weight is expressed, that
will be removed by the expansive force of Freezing? Whereunto an Inquiry is
subjoyned, whence this prodigious force, observed in water, expanded by
Glaciation, should proceed? And whether this _Phaenomenon_ may be solved,
either by the _Cartesian_, or _Epicurean_ Hypothesis?
11, What is the _Sphere of Activity_ of Cold, or the Space, to whose
extremities every way the Action of a cold Body is able to reach: where the
difficulty of determining these limits, together with the causes thereof,
being with much circumspection mentioned, it is observed, that the _Sphere
of Activity_ of Cold is exceeding narrow, not only in comparison of that of
Heat in Fire, but in comparison of, as it were, the _Atmosphere_ of many
odorous Bodies; and even in comparison of the _Sphere of Activity_ of the
more vigorous Loadstones, insomuch, that the Author hath doubted, whether
the Sense could discern a Cold Body, otherwise then by immediate Contract.
Where several Experiments are delivered for the examining of this matter,
together with a curious relation of the way used in _Persia_, though a very
hot Climate, to furnish their _Conservatories_ with solid pieces of Ice of
a considerable thickness: To which is added an Observation, how far in
Earth and Water the Frost will pierce downwards, and upon what accounts the
deepness of the Frost may vary. After which, the care is inculcated, that
must be had, in examining, whether Cold may be diffused through all
_Mediums_ indefinitely, not to make the Trials with _Mediums_ of two great
thickness: where it is made to appear, that Cold is able to operate through
Metalline Vessels, which is confirmed by a very pretty Experiment of making
_Icy Cups_ to drink in, whereof the way is accurately set down. Then are
related the Trials, whether, or how, Cold will be diffused through a
_Medium_, that _some_ would think a _Vacuum_, and which to _others_ would
seem much less disposed to assist the diffusion of Cold, than Common Air it
self. After which follows a curious Experiment, shewing whether a Cold Body
can operate through {51} a _Medium_ actually hot, and having its heat
continually renewed by a fountain of heat.
12, How to estimate the solidity of the Body of Ice, or how strong is the
mutual adhesion of its parts? and whether differing Degrees of Cold may not
vary the Degree of the compactness of Ice. And our Author having proceeded
as far as he was able towards the bringing the strength of Ice to some
Estimate by several experiments, he communicateth the information, he could
get about this matter among the Descriptions that are given us of cold
Regions: and then he relateth out of Sea-mens _Journals_, their
Observations touching the insipidness of resolved Ice made of Sea-water;
and the prodigious bigness of it, extending even to the height of two
hundred and forty Foot above water, and the length of above eight Leagues.
To which he adds some promiscuous, but very notable Observations concerning
Ice, not so readily reducible to the foregoing Heads: _videlicet_, Of the
blew colour of Rocky pieces of Ice; and the horrid noise made by the
breaking of Ice, like that of Thunder and Earthquakes, together with a
Consideration of the cause, whence those loud Ruptures may proceed.
13, How Ice and Snow may be made to last long; and what Liquor dissolves
Ice sooner than others, and in what proportion of quickness the Solutions
in the several Liquors are made, where occasion is offered to the Author,
to examine, whether Motion will impart a heat to Ice? After which he
relates an Experiment of _Heating_ a _Cold_ Liquor with Ice, made by
himself in the presence of a great and Learned Nobleman, and his Lady, who
found the Glass wherein the Liquor was, so hot that they could not endure
to hold it in their Hands. Next it is examined, whether the effects of Cold
do continually depend upon the actual presence and influence of the
manifest Efficient causes, as the Light of the Air depends upon the Sun or
Fire, or other Luminous Bodies. To this is annexed an Account of the
_Italian_ way of making _Conservatories_ of Ice and Snow, as the Author had
received it from that Ingenious and Polite Gentleman, Master _J. Evelyn_.
{52}
But want of time prohibiting the accomplishment of the intended account of
this Rich Piece: what remains, must be referred to the next Occasion. It
shall only be intimated for a Conclusion, that the _Author_ hath annexed to
this _Treatise_, an Examen of Master _Hob_'s Doctrine touching _Cold_;
wherein the _Grand_ Cause of _Cold_ and its Effects is assigned to _Wind_,
in so much that 'tis affirmed, that almost any Ventilation and stirring of
the Air doth refrigerate.
* * * * *
_LONDON,_
Printed with Licence, By _John Martyn_, and _James Allestry_, Printers to
the _Royal-Society_, 1665
{53}
* * * * *
_Numb._ 4.
PHILOSOPHICAL
_TRANSACTIONS._
* * * * *
_Munday_, _June_ 5. 1665.
* * * * *
The Contents.
_A Relation of some extraordinary Tydes in the _West Isles_ of
_Scotland_, by Sr. _Robert Moray_. The judgment of Monsieur _Auzout_,
touching the _Apertures_ of _Object-glasses_, and their _proportions_
in respect of the several lengths of _Telescopes_; together with a
_Table_ thereof. Considerations of the same Person upon Mr. _Hook's_
New Engine for grinding of _Optick-glasses_. Mr. _Hook's_ Thoughts
thereupon. Of a means to illuminate an _Object_ in what proportion one
pleaseth; and of the _distances_, that are requisite to burn Bodies by
the _Sun_. A further accompt by Monsieur _Auzout_ of Signior
_Campani_'s Book, and Performances about _Optick-Glasses_. _Campani_'s
Answer thereunto; and Mr. _Auzout_'s Animadversions upon that Answer.
An accompt of Mr. _Lower_'s newly published _Vindication_ of Dr.
_Willis_'s Diatriba de _Febribus_._
* * * * *
_A Relation of some extraordinary Tydes in the West-Isles of _Scotland_, as
it was communicated by Sr. _Robert Moray_._
In that Tract of _Isles_, on the West of _Scotland_, called by the
Inhabitants, the _Long-Island_, as being about 100. miles long from _North_
to _South_, there is a multitude of small Islands, situated in a _Fretum_,
or _Frith_, that passes between the Island of _Eust_, and the _Herris_;
amongst which, there is one called _Berneray_, some three miles long, and
{54} more than a mile broad, the length running from _East_ to _West_, as
the _Frith_ lyes. At the _East_ end of this _Island_, where I stayed some
16. or 17. dayes, I _observed_ a very strange Reciprocation of the Flux and
Re-flux of the Sea, and _heard_ of another, no less remarkable.
Upon the _West_ side of the _Long Island_, the Tides, which came from the
_South-west_, run along the Coast, _Northward_; so that during the ordinary
course of the Tides, the Flood runs _East_ in the _Frith_, where _Berneray_
lyes, and the Ebb _West_. And thus the Sea ebbs and flows orderly, some 4.
days before the _full Moon_, and _change_, and as long after (the ordinary
Spring-tides rising some 14. or 15. foot upright, and all the rest
proportionably, as in other places). But afterwards, some 4. days before
the _Quarter-moons_, and as long after, there is constantly a great and
singular _variation_. For _then_, (a _Southerly_ Moon making there the full
Sea) the course of the Tide being _Eastward_, when it begins to flow, which
is about 91/2 of the Clock, not onely continues so till about 31/2 in the
afternoon, that it be high water, but, after it begins to ebb, the Current
runs on still _Eastward_, during the whole Ebb; so that it runs _Eastward_
12 hours together, that is, all day long, from about 91/2 in the morning, til
about 91/2 at night. But then, when the night-Tide begins to flow, the
Current turns, and runs _Westward_ all night, during both Floud & Ebb, for
some 12. hours more, as it did _Eastward_ the day before. And thus the
Reciprocations continue, one Floud and Ebb, running 12 hours _Eastward_,
and another twelve hours _Westward_, till 4. days before the _New_ and
_Full_ Moon; and then they resume their ordinary regular course as before,
running _East_, during the six hours of Floud, and _West_, during the six
of Ebb. And this I observed curiously, during my abode upon the place,
which was in the Moneth of _August_, as I remember.
But the Gentleman, to whom the _Island_ belongs at present, and divers of
his Brothers and Friends, knowing and discreet persons, and expert in all
such parts of Sea-matters, as other _Islanders_ commonly are, though I
shrewdly suspected their skill in Tides, when I had not yet seen what they
told me, and I have now related of these irregular Courses of the Tides,
did most confidently assure me, and so did every body I spake with {55}
about it, that there is yet another irregularity in the Tides, which never
fails, and is no less extraordinary, than what I have been mentioning:
which is, That, whereas between the _Vernal_ and _Autumnal Equinoxes_, that
is, for six Moneths together, the Course of irregular Tides about the
Quartermoons, is, to run all day, that is, twelve hours, as from about 91/2
to 91/2, 101/4 to 101/4 _&c. Eastward_, and all night, that is, twelve hours
more, _Westward_: during the other six Moneths, from the _Autumnal_ to the
_Vernal Equinox_, the Current runs all day _Westward_, and all Night
_Eastward_.
Of this, though I had not the opportunity to be an Eye-witness, as of the
other, yet I do not at all doubt, having received so credible Information
of it.
To penetrate into the _Causes_ of these strange Reciprocations of the
Tides, would require exact descriptions of the Situation, Shape, and Extent
of every piece of the adjacent Coasts of _Eust_ and _Herris_; the Rocks,
Sands, Shelves, Promontorys, Bays, Lakes, Depths, and other Circumstances
which I cannot now set down with any certainty, or accurateness; seeing,
they are to be found in no _Map_, neither had I any opportunity to survey
them; nor do they now occur to my Memory, as they did some years ago, when
upon occasion I ventured to make a _Map_ of this whole _Frith_ of
_Berneray_, which not having copied, I cannot adventure to beat it out
again.
* * * * *
__Monsieur Auzout_'s Judgment touching the Apertures of _Object-Glasses_,
and their _Proportions_, in respect of the several _Lengths_ of
_Telescopes_._
This Author, observing in a small _French Tract_ lately written by him to a
Countryman of his, Monsieur _L' Abbe Charles_; That great _Optick Glasses_
have almost never as great an _Aperture_ as the small ones, in proportion
to what they Magnifie, and that therefore they must be more dim; takes
occasion to inform {56} the _Reader_, that he hath found, that the
_Apertures_, which _Optick-Glasses_ can bear with distinctness, are in
about a _subduplicate proportion_ to their _Lengths_; whereof he tells us
he intends to give the reason and demonstration in his _Diopticks_, which
he is now writing, and intends to finish, as soon as his Health will
permit. In the mean time, he presents the _Reader_ with a _Table_ of such
_Apertures_; which is here exhibited to the Consideration of the Ingenious,
there being of this _French_ Book but one Copy, that is known, in
_England_.
A _TABLE_ of the _Apertures_ of _Object-Glasses_.
_The Points put to some of these Numbers denote Fractions._
Lengths of |For excellent| For good |For ordinary |
Glasses. | ones. | ones. | ones. |
Feet, Inches.|Inch, Lines.|Inch, Lines.|Inch, Lines.|
| | | |
4| 4.| 4| 3|
6| 5.| 5| 4|
9| 7| 6| 5|
1 0| 8.| 7| 6|
-------------|-------------|-------------|-------------|
1 6| 9| 8.| 7|
2 0| 11| 10| 8|
2 6|1 0| 11| 9|
3 0|1 1|1 0| 10|
-------------|-------------|-------------|-------------|
3 6|1 2.|1 1| 11|
4 0|1 4|1 2|1 0|
4 6|1 5|1 3|1 .|
5 0|1 6|1 4|1 1.|
-------------|-------------|-------------|-------------|
6 |1 7.|1 5|1 2|
7 |1 9|1 6|1 3|
8 |1 10|1 8|1 4|
9 |1 11.|1 9|1 5|
-------------|-------------|-------------|-------------|
10 |2 1|1 10|1 6|
12 |2 4|2 0|1 8|
14 |2 6|2 2|1 9.|
16 |2 8|2 4|1 11.|
18 |2 10|2 6|2 1|
20 |3 0|2 7|2 2.|
-------------|-------------|-------------|-------------|
25 |3 4|2 10|2 4.|
30 |3 8|3 2|2 7|
35 |4 0|3 4.|2 10|
40 |4 3|3 7|3 .|
-------------|-------------|-------------|-------------|
45 |4 6|3 10|3 2.|
50 |4 9|4 0|3 4.|
55 |5 0|4 3|3 6.|
60 |5 2|4 6|3 8.|
-------------|-------------|-------------|-------------|
65 |5 4|4 8|3 10|
70 |5 7|4 10|4 .|
75 |5 9|5 0|4 2.|
80 |5 11|5 2|4 5|
-------------|-------------|-------------|-------------|
90 |6 4|5 6|4 7.|
100 |6 8|5 9|4 10|
120 |7 5|6 5|5 3|
150 |8 0|7 0|5 11|
-------------|-------------|-------------|-------------|
200 |9 6|8 0|6 9|
250 |10 6|9 2|7 8.|
300 |11 6|10 0|8 5|
350 |12 *6.|10 9|9 0|
400 |13 4|11 6|9 8|
-------------+-------------+-------------+-------------+
{57}
* * * * *
_Considerations of Monsieur _Auzout_ upon Mr. _Hook_'s New Instrument for
Grinding of _Optick-Glasses_._
In the above-mentioned _French_ Tract, there are, besides several other
particulars, to be represented in due place, contained some
_Considerations_ of Monsieur _Auzout_ upon Mr. _Hook_'s New _Engine_ for
grinding _Optick-Glasses_. Where he premises in _General_ his thoughts
touching the working of _Great_ Optick-Glasses, and that by the help of a
_Turn lathe_; affirming first of all, that not only the _Engin_ is to be
considered for giveing the _Figure_, but the _Matter_ also, which ought to
be brought to greater perfection, than it hath been hitherto. For, he finds
it not so easie (as least, _where he is_) to procure _Great_ pieces of
Glass without _Veins_, and other faults, nor to get such, as are thick
enough without _Blebbs_; which, if they be not, they will yield to the
pressure and weight, either when they are fitted to the _Cement_, or
wrought.
Secondly, He finds it difficult to work these _Great_ Glasses of the _same_
thickness, which yet is very necessary, because, that the least difference
in _Figures_ so little _convex_, can put the _Center_ out of the _Midle_, 2
or 3 _Inches_; and if they be wrought in _Moulds_, the length of time,
which is required to wear and to smooth them, may spoil the best _Mould_,
before they be finished. Besides, that the strength of Man is so limited,
that he is unable to work Glasses beyond a certain bigness, so as to finish
and polish them all over so well, as _small_ Glasses; whereas yet, the
bigger they are, the more compleat they ought to be: And if any weight or
Engine be used to supply strength, there is then danger of an unequal
pressure, and of wearing away the Engine; In the mean time, the preciseness
and delicateness is {58} greater than can easily be imagined. Wherefore he
could never, having some experience of this preciseness, conceive, that a
_Turn-lathe_, wherein must be two different, and in some manner contrary
motions, can move with that exactness and steddiness, that is required,
especially, for any considerable length of time.
Having premised this, he discourses upon Mr. _Hook_ his _Turne_, intimating
first of all, that he was impatient to know what kind of _Turne_ this was,
imagining, that it had been tried, and had succeeded, as coming from a
Society that professeth, they publish nothing but what hath been maturely
examin'd. But that he was much surprised when he saw the _Micrography_ of
Mr. _Hook_, and found there, that his _Engine_ was published upon a _meer
Theory_, without having made any Experiment, though that might have been
made with little charge and great speed; expence of Money and Time being
the onely thing, that can excuse those who in matter of _Engines_ impart
their inventions to the publick, without having tried them, to excite
others to make trial thereof.
Whereupon he proposes some difficulties, to give the _Inventor_ occasion to
find a way to remove them. He affirms therefore, that though it be true in
the _Theory_, that a _Circle_, whose _Plain_ is inclined to the _Axis_ of
the _Sphere_ by an _Angle_, whereof half the _Diameter_ is the _Sine_, and
which touches the _Sphere_ in its _Pole_, will touch in all its parts a
_spherical Surface_, that shall turn upon that _Axe_. But that it is true
also, that that must be but a _Mathematical Circle_, and without _Breadth_,
and which precisely touches the Body in its middle: Whereas in the
practice, a _Circle_ capable to keep Sand and Putty, must be of some
_breadth_; and he knows not whether we can find such a dexterity of keeping
so much of it, and for so long a time, as needs, upon the Brim of a _Ring_
that is half an Inch broad. He adds, that it is very difficult to contrive,
that the middle of the Glass do always precisely answer to the Brim of this
_Ring_, seeing that the position of the Glass does always change a little
in respect of the _Ring_, in proportion as 'tis worn, and as it must be
pressed because of its inclination. He believes it also very hard, to give
to the _Axis_ or to the _Mandril_, which holds the Glass, that little {59}
_Inclination_, that would be necessary for great Glasses, and to make the
two _Mandrils_ to have one and the same _Plain_, as is necessary. And,
having done all this, he persuades himself, that it is exceedingly
difficult, if not impossible, for two contrary motions, where so many
pieces are, to rest for a long time steddy and firm, as is requisite for
the not swarving from it a hair's thickness, since less than that can
change all.
He goes on, and, seeing that this _Inventor_ speaks of Glasses of a
thousand, & ten thousand foot, which he supposed not impossible to be made
by this _Engine_, discourses of what is necessary for the making Glasses of
such bignesses; which he believes this _Inventor_ may perhaps not have
thought of. Wherefore he affirms, that if the _Table_, made by himself for
the _Apertures_ of Glasses (which is that, that is above delivered) be
continued unto a thousand feet, by taking always the _Subduplicate
proportion_ of _Lengths_, it will be found, that for pretty good ones, the
_Aperture_ must be of 15. Inches; for good ones, more than 18. and for such
as are excellent, more than 21. Inches: whence it may be judged, what piece
of Glass, and of what thickness it must be, to endure the working. But he
proceeds to speak of the _Inclination_, which the _Mandril_ must have upon
the _Plain_ of the _Ring_, when the _Ring_ should have 10. or 12 Inches;
and finds, that it would make but 6 or 7. minutes of inclination, and that
a Glass would have less _Convexity_, and consequently, less difference from
a Glass perfectly plain, than the 7. or 8. part of a Line. And then he
leaveth it to be judged, whether a Glass of such a Length being found, we
ought to hope, that a _Turn_ can be firm enough to keep such a piece of
Glass in the same Inclination, so that a _Mandril_ do not recede some
Minutes from it: and, though even the Glass could be fastned perfectly
perpendicular to the _Mandril_, that those two _Mandrils_ could be put in
one and the same Plain, & that that little Inclination, which is requisite,
could be given, and the _Mandril_ be continued to be pressed in that same
_Inclination_, according as the Glass is worn. All which particulars, he
conceives to be very hard in the practice; not to mention, that the weight
of the Glass, that should be inclined to the _Horizon_, as 'tis represented
by Mr. _Hook_, would make it slide upon the _Cement_, and so {60} change
the _Center_; and that the Glass is not pressed at the same time by the
_Ring_ but in one part on the side, _vid._ about a fourth; and that the
parts of the Glass are not equally worn away, &c. What then, _saith he_,
would becom of a Glass of 10000 feet, which, according to the said Table,
would have more than four feet, or four feet and nine inches, or five feet,
seven inches _Aperture_, and of which the _Ring_, though it were two feet
nine inches, would have but one minut of _Inclination_, and the Glass of 5
feet _Aperture_ would have but 4 minuts, and the curvity of it would be
less than the eight part of a Line.
But, _saith he_, let us consider, only a Glass of 300 foot, to see, what is
to be hoped of that, and to know at least the difficulty, to be met with in
making a Glass only of that Length. A Glass then of 300 foot, according to
his Table, must have more than 8 inches _Aperture_, which maketh but 16
minuts of its _Circle_, and it should have more than 11 inches, if it be an
excellent one. If Mr. _Hook_ (adds he) did use but his _Ring_ of 6 inches,
which he would use from twelve to an hundred foot Glass, the _Inclination_,
which the _Axis_, or _Mandril_, that bears his Glass, should have, should
be but 16 minuts, and the _Curvity_ of the Glass would be less than the
eighth part of a Line, and if he should use a bigger, the _Inclination_
would be proportionable.
Whence it may be judged (continues he) that we are yet very far from seeing
_Animals &c._ in the _Moon_, as Monsieur _Des Cartes_ gave hope, and Mr.
_Hook_ despairs not of. For, he believes by what he knows of _Telescopes_,
that we are not to look for any above 300 or 400 foot at most; and he
fears, that neither _Matter_ nor _Art_ will go even so far.
When therefore (_saith he_) a Glass of 300 foot should bear an Eye-glass of
6 inches (which would appear wonderful) it would magnifie but 600. times in
_Diameter_, that is, 360000 times in _Surface_: but suppose, that such
could be made, as would magnifie a 1000 times in _Diameter_, and 1000000.
of times in _Surface_, admitting there were but 60000 leagues from the
_Earth_ to the _Moon_, and that the smalness of the _Aperture_ of the
Glasses (which yet would diminish the Light more than 36 times) and the
obstacle of the Air were not considered, we should not {61} see the _Moon_,
but as if we were a 100, or at least, 60. leagues distant from her without
a Glass. He here wishes, that those, that promise to make us see _Animals_
and _Plants_ in the Moon, had thought on what our naked Eyes can make us
discern of such Objects, only at 10 or 12 leagues distance.
But this he would not have understood as a discouragement from searching
with all care and earnestness after the means of making long _Telescopes_,
or of facilitating the working thereof; but only as an Advertisement to
those, who light upon the _Theory_ of any _Engine_, not to expose it
presently as possible and useful, before they have tried it, or if it have
succeeded in small, not to endeavour to persuade, that it will also succeed
in great.
As it may happen (_saith he_) that the Engin of Mr. _Hook_ may, by using
all necessary precautions, succeed in the making of _Eye-Glasses_, or
_small_ Optick-Glasses, but not in making _great_ ones; as we see, that an
instrument composed of two Rulers, wherewith are traced Portions of
Circles, succeeds well enough in _small_, but when there is no more than
half a Line, a quarter of a Line, or less convexity, it will be no longer
just at all, as he tells us to have made the proof of it in Circles drawn
by the means of one of these Instruments, made by one of the best Workmen
in his time, who, whilst he lived, esteemed them above price, although they
be not just; as others and my self (_saith he_) have by tryal found, when
we endeavoured to make _Moulds_ by their means, & as those, who by the like
Instrument laboured to trace portions of Circles of 80 or 100 foot, _&c.
Diameter_, can attest.
But, notwithstanding all this, he hath thought upon two or three things,
which he thinks may remedy some inconveniencies of Mr. _Hook_ his _Turn_.
The _first_ is, to invert the Glass, and to put it under the _Ring_, that
so not only the Glass may be placed more _Horizontally_, and not slide upon
the _Cement_, but that the _Sand_ also, and the _Putty_ may stay upon the
Glass.
The _other_ is, that there must be two _Poppetheads_, into which the
_Mandril_ must pass, where the _Ring_ is to be fastned; and the _Mandril_
must be perfectly _Cylindrical_, that so it may advance upon the Glass as
it wears away by the means of its weight, or by the means of a spring,
pressing it, without wrigling from one place to another, as it would
presently happen in the fashion, {62} as the _Turn_ is composed. For, when
the Glasses do wear, especially when they are very _convex_, it cannot be
otherwise, but the _Mandril_ will play and wrigle, before the _Scrue_ be
made firm.
But he doubts, whether all can be remedied, which he leavs to the industry
of Mr. _Hook_, considering what he saith in the _Preface_ of his
_Micrography_, touching a Method, he knows, of finding out as much in
_Mechanicks_, as can be found in _Geometry_ by _Algebra_.
Besides this, he taketh notice, that most of those that medle with
_Optick-Glasses_, give them not as much _Aperture_, nor charge them so deep
as they ought. And he instances in the _Telescope_, which His _Majesty_ of
_Great Britain_ presented the _Duke_ of _Orleans_ with, _videl._ that it
did bear but 2 inches, and 9 lines _French_, for its greatest _Aperture_,
though there be 5 or 6 lesser _Apertures_, of which it seems (_saith he_)
the Artificer would have those, that use it, serve themselves more
ordinarily, than of the greatest; which conveys but almost half as many
Rays as it should do, according to his Calculation, which is, as 9 to 16;
Whereas, according to his _Table_ of _Apertures_, an excellent 35 foot
_Telescope_ should bear 4 inches _Aperture_ in proportion to _excellent_
small ones. He notes also, that the Eye-glass of the said _Telescope_,
composed of 2 Glasses, hath no more effect, when it is most charged, than a
Glass of 41/2 inches; which makes it magnifie not a 100 times. And he finds
by Mr. _Hook_, that he esteems a _Telescope_ made in _London_ of 60 feet,
(which amount to about 57 feet of _France_, the foot of _France_ being to
that of _England_ as about 15 to 16) because it can bear at least 3
_English_ inches _Aperture_, and that there are few of 30 feet, that can
bear more than 2 inches, (which is but 221/2 Lines _French_) although he (M.
_Auzout_) gives no less _Aperture_ than so, to a 15 foot-_Telescope_, and
his of 21 feet hath ordinarily 2 Inches, 4 Lines, or 2 inches, 6 Lines
_Aperture_.
This Discourse he Concludeth with exhorting those, that work
_Optick-Glasses_, to endeavor to make them such, that they may bear great
_Apertures_ and deep Eye-glasses; seeing it is not the length that gives
esteem to _Telescopes_; but on the contrary renders them less estimable, by
reason of the trouble {63} accompanying them, if they perform no more, than
shorter ones. Where, by the by, he takes notice, that he knows not yet,
what _Aperture_ Signor _Campani_ gives to his Glasses, seeing he hath as
yet signified nothing of it; but that the small one, sent by him to
Cardinal _Antonio_, hath no more _Aperture_, than ordinary ones ought to
have.
He promises withall, that he will explicate this way in his _Treatise of
the usefulness of Telescopes_, where he intends to assign the Bigness of
the _Diameter_ of all the _Planets_, and their proportion to that of the
_Sun_; as also, that of the _Stars_, which he esteems yet much less, than
all those have done, that have written of it hitherto; not believing, that
the _Great Dog_, which appears to be the fairest Star of the _Firmament_,
hath 2 _Seconds_ in _Diameter_, nor that those, which are counted of the
sixth Magnitude, have 20 _thirds_; nor thinking, that all the Stars, that
are in the _Firmament_, do enlighten the Earth as much as a Luminous Body
of 20 _seconds_ in _Diameter_ would do, or, because there is but one half
of them at the same time above our _Horizon_, as a Body of 14 _seconds_ in
_Diameter_; and as the 18432^{th} part of the _Sun_ would enlighten us, or
as the _Sun_ would do, if we were 14 times more distant from it, than
_Saturn_, and 137 times further, than the Earth: Which, _he saith_, would
not be credible, if he did not endeavor to evince it both by _Experience_
and _Reason_. And he doubts not, but that _Venus_, although she sends us no
Light but what is reflected, does sometimes enlighten the _Earth_ more,
than all the Stars together. Yet he would not have us imagine, from what he
hath spoken of the smallness of the Stars, that _Telescopes_ do not
magnifie them by reason of their great distance, as they do _Planets_; for
this he judgeth a Vulgar Error, to be renounced. _Telescopes_ magnifie the
_Stars_ (_saith he_) as much in proportion, as they do all other Bodies,
seeing that the demonstration of their magnifying is made even upon
_Parallel_ rays, which do suppose an infinite distance, though the Stars
have none such: And if the _Telescopes_ did not magnifie the Stars, how
could they make us see some of the _fiftieth_, and it may be some of the
_hundreth_, and _twohundreth_ Magnitude, as they do, and as they would shew
yet much lesser ones, if they did magnifie more? {64}
* * * * *
__M^r. Hook_'s Answer to Monsieur _Auzout_'s Considerations, in a Letter to
the Publisher of these _Transactions_._
_SIR_,
Together with my most hearty thanks for the favour you were pleased to do
me, in sending me an _Epitome_ of what had been by the ingenious Monsieur
_Auzout_ animadverted on a description, I had made of an _Engine_ for
_grinding spherical Glasses_, I thought my self obliged, both for your
satisfaction, and my own Vindication, to return you my present thoughts
upon those Objections. The chief of which seems to be against the very
_Proposition_ it self: For it appears, that the _Objector_ is somewhat
unsatisfied, that I should propound a thing in _Theory_, without having
first tried the _Practicableness_ of it. But first, I could wish that this
worthy Person had rectified my mistakes, not by speculation, but by
experiments. Next, I have this to answer, that (though I did not tell the
_Reader_ so much, to the end that he might have the more freedom to examine
and judg of the contrivance, yet) it was not meer _Theory_ I propounded,
but somewhat of _History_ and _matter of Fact_: For, I had made trials, as
many as my leisure would permit, not without some good success; but not
having time and opportunity enough to prosecute them, I thought it would
not be unacceptable to such, as enjoyed both, to have a description of a
way altogether _New_, and _Geometrically_ true, and seemingly, not
unpracticable, whereof they might make use, or not, as they should see
reason. But nothing surprised me so much, as, that he is pleased (after he
had declared it a fault, to write this _Theory_, without having reduced it
to practice) to lay it, as he seems to do, in one place of his book, _p._
22 upon the _Royal Society_. Truly, _Sir_, I should think my self most
injurious to that _Noble Company_, had I not endeavoured, even in the
beginning of my Book, to prevent such a misconstruction. And therefore I
cannot but make this interpretation of what Monsieur _Auzout_ saith in this
particular, that either he had not so {65} much of the Language wherein I
have written, as to understand all what was said by me, or, that he had not
read my _Dedication_ to the _Royal Society_, which if he had done, he would
have found, how careful I was, that that _Illustrious Society_ should not
be prejudiced by my _Errors_, that could be so little advantaged by my
_Actions_. And indeed, for any man to look upon the matters published by
their Order or Licence, as if they were _Their_ Sense, and had _Their_
Approbation, as _certain_ and _true_, 'tis extremely wide of their
intentions, seeing they, in giving way to, or encouraging such
publications, aim chiefly at this, that _ingenious conceptions_, and
important _philosophical matter of Fact_ may be communicated to the learned
and enquiring World, thereby to excite the minds of men to the examination
and improvement thereof. But, to return; As to his _Objections_ against the
_Matter_, I do find that they are no more against mine, than any other way
of _Grinding Glasses_; nor is it more than I have taken notice of my self
in this Passage of the same _Paragraph_, of which sort are also those
difficulties he raises about _Long Glasses_, which are commonly known to
such, as are conversant in making them _It would be convenient also_ (these
are my words) _and not very chargeable, to have four or five several Tools:
One,_ &c. _And, if curiosity shall ever proceed so farr, one for all
lengths, between 1000. and 10000. foot long; for indeed, the _Principle_ is
such, that supposing _the Mandrils well_ made, and of a good length, and
supposing _great care_ be used in working and polishing them, I see no
reason, but that a Glass of 1000. nay, 10000. foot long may be made, as
well as one of 10. For, the reason is the same, supposing the _Mandrils_
and _Tools_ be made sufficiently strong, so that they cannot bend; and
supposing also that the Glass out of which they are wrought, be capable of
so great a regularity in its parts, as to its Refraction._ But next, I must
say that his _Objections_ to me, seem not so considerable, as perhaps he
imagines them. For, as to the possibility of getting Plates of Glass thick
and broad enough without veins, I think _that_ not now so difficult here in
_England_, where I believe is made as good, if not much better Glass for
_Optical Experiments_, than ever I saw come from _Venice_. Next, though it
were better, that the thickest part of a long _Object-Glass_ were exactly
in the middle, yet I can assure Monsieur _Auzout_, that it may be a very
{66} good one, when it is an Inch or two out of it. And I have a good one
by me at present, of 36. foot, that will bare an _Aperture_, if _Saturn_ or
the _Moon_ in the _twilight_, be look'd on with it, of 31/2 Inches over, and
yet the thickest part of the Glass is a great way out of the middle. And I
must take the liberty to doubt, whether ever my _Animadversor_ saw a long
Glass, that was otherwise; as he might presently satisfie himself by a way
I could shew him (if he did not know it) whereby the difference of the
thickness of the sides might be found to the hundreth part of a Line.
As to the exceeding exactness of the _Figure_ of Long _Object-Glasses_,
'tis not doubted, but that it is a matter difficult enough to be attained
any way: but yet, I think, much easier by _Engine_, than by _Hand_; and of
all _Engines_, I conceive, none more plain and simple, than that of a
_Mandril_. And for making _spherical Glasses_ by an _Engine_, I am apt to
think, there hardly can be any way more plain, and more exact, than that
which I have described; wherein there is no other motion, than that of two
such _Mandrils_, which may be made of sufficient strength, length, and
exactness, to perform abundantly much more, than I can believe possible to
be done otherwise than by chance, by a man's hands or strength unassisted
by an _Engine_, the motion and strength being much more certain and
regular. I know very well, that in making a 60. foot Glass by the strength
of the hand, in the common way, not one of ten that are wrought, will
happen to be good, as I have been assured by Mr. _Reeves_; who, I am apt to
think, was the first that made any good of that length. For the _Figure_ of
the _Tool_ in that way is presently vitiated by the working of the Glass,
and without much _gaging_ will not do any thing considerable. Besides, the
strength of a man's hands, applied to it for the working and polishing of
it, is very unequal, and the motions made, are very irregular; but in the
way, I have ventured to propose, by _Mandrils_, the longer the _Glass_ and
_Tool_ are wrought together, the more exact they seem to be and if all
things be ordered, as they should be, the very polishing of the Glass, does
seem most of all rectifie the _Figure_.
As to what he objects, that the Tool does only touch the Glass in a
_Mathematical Circle_; that is true, perhaps, at first, but before the
Glass is wrought down to its true _Figure_, the _Edge_ of the _Tool_ {67}
will be worn or grownd away, so as that a Ring of an inch broad may be made
to touch the _Spherical Surface_ of the Glass; nay, if it be necessary
(without much trouble, especially in the grinding of longer Glasses) the
whole _Concave Surface_ of the _Tool_ may be made to touch a Glass.
Besides, that as to the keeping a quantity of the same sand and Powders of
several finesses, according as the glass wears, the same is possible to be
don, as with the same Sand wrought finer by working in the Ordinary way.
The giving the _Inclination_ to the _Mandrils_, is not at all difficult;
though perhaps to determine the length exactly which the Glass so made
shall draw, is not so easie: But 'tis no matter, what length the Glass be
off, so it be made good, whether 60 or 80 foot, or the like. Nor is it so
very difficult, to lay them both in the same _Plain_. And to keep them
_steddy_, when once fix'd, is most easie.
As to the Calculation of the propriety of a Glass of a thousand foot,
perhaps for that particular Length, I had not, nor have as yet calculated,
that the Convexity of one of eighteen inches broad, will not be above a
seventh part of a Line. But it does not thence follow, that I had not
considered the difficulties, that would be in making of it. For, I must
tell him, that I can make a _Plano convex_ Glass though its convexity be a
smaler sphere than is usual for such a length to be an _Object-Glass_ of
about 150 foot in Length, nay of 300 foot, and either longer or shorter,
_without_ at all _altering the convexity_. So that, if he will by any
Contrivance he hath, give me a _Plano-convex_ Glass of 20, or 40 foot
_Diameter_, without _Veins_, and truly wrought of that _Figure_, I will
presently make a _Telescope_ with it, that with a single Ey-glass shall
draw a thousand foot: Which _Invention_, I shall shortly discover, there
being, I think, nothing more easie and certain. And if a _Plano-convex_
Glass can be made of any _Sphere_ between twenty and fourty foot _radius_,
so as that both the _Convex_ and _Plain_ side of the Glass be exactly
polish'd of a true _Figure_, I will shortly shew, how therewith may be made
a _Telescope_ of any Length, supposing the Glass free from all kind of
_Veins_, or inequality of _Refraction_.
As for the sliding of the Glass upon the _Cement_, I see no reason at all
for it, at least in the _Cement_, I make use of, having never observed any
such accident in hard _Cement_. {68}
And for the Bearing of the _Ring_ against one side of the Glass only at a
time, I cannot see, why _that_ should produce any inequality, since all the
sides of the Glass have successively the same pressure.
His ratiocination concerning a Glass of 300 foot, is much the same with the
former, about the difficulty of working a true surface of a convenient
figure; which how considerable both _that_ and his Conclusion thereupon
(_videl. That we are not to expect Glasses of above 300 or 400 foot long at
most, and that neither _Matter_ nor _Art_ will go so far_) is, may be
judged from what I have newly told you of making any _Object-Glass_ of any
Length.
And for his good wishes, that those, who promise to make him see _Plants_
or _Animals_ in the _Moon_ (of which I know not any, that has done so,
though perhaps there may be some, notwithstanding his Objections, that do
not yet think it impossible to be done) had considered, what a Man is able
to see with his _bare_ Eye at 60 Leagues distance: I cannot but return him
my wishes, that he would consider the difference between seeing a thing
through the _Gross_ and _Vaporous_ Air neer the Earth, and through the Air
over our heads: Which, if he observe the Moon in the _Horizon_, and neer
the _Zenith_ with a _Telescope_, he will experimentally find; and, having
done so, he will perhaps not be so dissident in this matter.
Concerning his Advertisement to such, as publish _Theories_, I find not,
that he hath made use of it in his own case. For, in his _Theory_ about
_Apertures_ he seems to be very positive, not at all doubting to rely upon
it, _vid._ that the _Apertures_ must be _thus_ and _thus_ in _great_
Glasses, because he had found them _so_ or _so_ in some _small_ ones.
For his Proposal of amendments of some inconveniencies in this way, I
return him my thanks; but as to his first I believe, that the matter may be
conteined as wel in the _Concave_ Tool, as on the _convex_ Glass. And as to
that of 2 _Poppet-heads_ I do not well understand it, if differing from
mine; and the keeping of the Tool upon the Glass with a spring or weight,
must quickly spoyl the whole; since, if either of the _Mandrils_ will
easily yield backwards, the _regularity_ of _all_ will be spoiled: and as
to the wrigling and playing of the _Mandril_, I do not at all apprehend it.
{69}
His _Theory_ of _Apertures_, though he seems to think it very authentick,
yet to me it seems not so cleer. For, the same Glass will endure greater or
lesser _Apertures_, according to the lesser or greater Light of the
_Object_: If it be for the looking on the _Sun_ or _Venus_, or for seeing
the _Diameters_ of the _Fix'd Stars_, then smaller _Apertures_ do better;
if for the _Moon_ in the _daylight_, or on _Saturn_, or _Jupiter_, or
_Mars_, then the largest. Thus I have often made use of a 12 foot-Glass to
look on _Saturn_ with an _Aperture_ of almost 3 inches, and with a single
Eye-glass of 2 inches _double convex_: but, when with the same Glass I
looked on the _Sun_ or _Venus_, I used both a smaller _Aperture_, and
shallower _Charge_. And though M. _Auzout_ seems to find fault with the
_English_ Glass of 36 foot, that had an _Aperture_ of but 23/4 inches
_French_; as also, with a 60 foot _Tube_, used but with an _Aperture_ of 3
inches; yet I do not find, that he hath seen Glasses of that length, that
would bear greater _Apertures_, and 'tis not impossible, but his _Theory_
of _Apertures_ may fail in longer Glasses.
* * * * *
_Of a means to illuminate an Object in what proportion one pleaseth; and of
the Distances requisite to burn Bodies by the _Sun_._
One of the means used by M. _Auzout_ to enlighten an Object, in what
proportion one pleaseth, is by some great _Object-Glass_, by him called a
_Planetary_ one, because that by it he shews the difference of Light, which
all the _Planets_ receive from the _Sun_, by making use of several
_Apertures_, proportionate to their distance from the _Sun_, provided that
for every 9 foot draught, or thereabout, one inch of _Aperture_ be given
for the _Earth_. Doing this, one sees (_saith he_) that the Light which
_Mercury_ receives, is far enough from being able to burn Bodies, and yet
that the same Light is great enough in _Saturn_ to see cleer there, seeing
that (to him) it appears greater in _Saturn_, than it doth upon our
_Earth_, when it is overcast with Clouds: Which (he adds) would scarce be
believed, if by means of this Glass it did not sensibly appear so; Whereof
he promises to discourse more fully in his {70} _Treatise of the usefulness
of great Optick-Glasses_, where he also intends to deliver several
Experiments, by him made, 1. Touching the quantity of Light, which a Body,
that is 10, 15 and 20 times, &c. remoter than _Saturn_, would yet receive
from the _Sun_. 2. Touching the quantity of Light, by which the _Earth_ is
illuminated even in the _Eclipses_ of the _Sun_, in proportion of their
bigness. 3. Touching the quantity of Light, which is necessary to burn
Bodies: he having found, that not abating the Light, which is reflected by
the Surfaces of the Glass (whereof he confesseth, he doth not yet exactly
know the quantity) there would be necessary about 50 times as much Light,
as we have here, for the burning of _Black_ Bodies; and neer 9 times more
for the burning of _White_ Bodies, than for the burning of _Black_ ones:
and so observing the immediate proportions between these two, for burning
bodies of _other_ Colors. Whence (he tells us) he hath drawn some
consequences, touching the distance, at which we may hope, to burn Bodies
here, by the means of _great Glasses_ and great _Looking-glasses_. So that
(_saith he_) we must yet be seven times neerer the _Sun_, than we are, to
be in danger of being burned by it. Where he mentions, that having given
_Instructions_ to certain persons, gon to travel in _Hot Countries_, he
hath among other particulars recommended to them, to try by means of great
_Burning-glasses_, with how much less _Aperture_ they will burn _there_,
than _here_, to know from thence, whether there by more Light _there_ than
_here_, and how much; since this perhaps may be the only means of trying
it, supposing, the same matters be used: although the difference of the Air
already heated, both in _hot Countries_, and in the _Planets_, that are
neerer than we, may alter, if not the quantity of Light, at least that of
the Heat, found there.
* * * * *
_A further Account, touching Signor _Campani_'s Book and Performances about
_Optick-glasses_._
In the above-mentioned _French_ Tract there is also conteined M. _Auzout's_
Opinion of what he had found New in the _Treatise_ of Signor _Campani_,
which was spoken of in the first _Papers_ of these _Transactions_,
concerning both the Effect of the _Telescopes_, contrived after a peculiar
way by the said _Campani_ at _Rome_, and {71} his New Observations of
_Saturn_ and _Jupiter_, made by means thereof.
First therefore, after that M _Auzout_ had raised some scruple against the
Contrivance of Signor _Campani_ for making _Great Optick-Glasses_ without
_Moulds_, by the means of a _Turn-lath_, he examines the _Observations_,
made with such _Glasses_: Where, having commended _Campani_'s sincerity in
relating what he thought to have seen in _Saturn_, without accomodating it
to M. _Hugens_'s _Hypothesis_, he affirms, that supposing, there be a
_Ring_ about _Saturn_, Signor _Campani_ could not see in all those
different times, that he observed it, _the same Appearances_, which he
notes to have _actually_ seen. For, having seen it sometimes in _Trine
Aspect_ with the _Sun_, and _Oriental_; sometimes, in the same _Aspect_,
but _Occidental_; sometimes in _Sextil Aspect_, and _Occidental_; at
another time, again in _Trine_, and _Oriental_, this Author cannot
conceive, how _Saturn_ could in all these different times have no
difference in its _Phasis_, or keep always the same _Shadow_; seeing that,
according to the _Hypothesis_ of the _Ring_, when it was _Oriental_, it
must cast the _Shadow_ upon the _left_ side of the _Ring_ beneath, without
casting any on the _right_ side: and when it was _Occidental_, it could not
but cast it on the _right_ side beneath, and nothing of it on the other.
Concerning the _Shadow above_, which _Campani_ affirms to be made by the
_Ring_ upon the Body of _Saturn_, M. _Auzout_ judges, that there could be
no such _Phaenomenon_, by reason of its _Northern Latitude_ at the times,
wherein the _Observations_ were made, _vid._ in _April_ 1663; in the midst
of _August_, and the beginning of _October_, next following, and in _April_
1664, except it were in _October_, and the _Shadow_ strong enough to become
_visible_.
But as to the _Shadow below_, he agrees with _Campani_, that it does
appear, yet not as he notes it, seeing that it must be sometimes on the one
side, sometimes on the other; and towards the _Quadrat_ with the _Sun_ it
must appear biggest, as _indeed_ he affirms to have seen it himself _this_
year, insomuch that sometimes it seemed to him, that it covered the whole
_Ring_, and that the _Shadow_, joyning with the obscure space between both,
did interrupt the circumference of the _Ring_; but beholding it at other
times in a cleer Sky, and when there was no Trepidation of the Air, {72} he
thought, that he saw also the Light continued from without, although very
slender. But he acknowledges, that he could never yet _precisely_
determine, by how much the largeness of the _Ring_ was bigger than the
_Diameter_ of _Saturn's_ Body. As for the proportion of the Length to the
Breadth, he affirms, to have alwaies estimated it to be two and a half, or
very neer so; and to have found in his _Observations_, that in _January_
last, one time, the length of _Saturn_ was 12 _Lines_, and the breadth 5.
Another time, the length was 12. _Lines_, and the breadth 4. and this by a
peculiar method of his own. But yet he acknowleges also, that sometimes he
hath estimated it as 7. to 3. and at other times as 13. to 5. and that if
there do not happen a change in the magnitude of the _Ring_ (as it is not
likely there does) that must needs proceed from the Constitution of the
air, or of the Glass's having more or less _Aperture_, or from the
difficulty of making an exact estimate of their proportions. However it is
not much wide (saith he) of two and a half, although _Campani_ make the
length of the _Ring_ but double to its breadth.
Monsieur _Auzout_ believes, that he was one of the first that have well
observed this shadow of _Saturn's_ Body upon its _Rings_ which he affirms
happened two years since; when, observing in _July_, for the first time,
with a _Telescope_ of 21. and then another of 27. foot, he perceived, that
the _Angle_ of the obscure space on the _right side_ beneath, was bigger
and wider, than the three other _Angles_, and that some interruption
appear'd _there_, between the _Ring_, and the _Body of Saturn_; of which he
saith to have given notice from that time to all his friends, and in
particular, as soon as conveniently he could, to Monsieur _Hugens_.
He confesseth, that he hath not had the opportunity of observing _Saturn_
in his _Oriental Quadrat_; yet he doubts not, but that the _shadow_ appears
on the _Left-side_, considering, that the _Existence_ of the _Ring_ can be
no longer doubted of, after so many _Observations_ of the _shadow_ cast by
_Saturn's_ Body upon it, according as it must happen, following that
_Hypothesis_; there being no reason, why it should cast the said _shadow_
on one side, and not on the other.
Concerning the Observation of _Jupiter_ and its _satellites_, the famous
_Astronomer_ of _Bononia_, _Cassinus_, having {73} published, that on the
30. day of _July_, 1664. at 21/2 of the clock in the morning, he had
observ'd, with _Campani_'s Glasses, that there passed through the broad
obscure _Belt_ of _Jupiter_ two obscurer _spots_, by him esteemed to be the
_shadows_ of the _Satellites_, moving between _Jupiter_ & the _Sun_, and
eclipsing him, and emerging from the Occidental Brim thereof: This
_Authour_ did first conceive, that they were not _shadows_, but some
_Sallies_, or _Prominencies_ in that _Belt_; which he was induced to
believe, because he perceived not, that that _Prominency_, which he there
saw, was so black, nor so round as _Cassini_ had represented his _spots_;
wherefore, seeing it but little differing in colour, from the _Belt_, and
so not judging it round, because it did stand only about half its diameter
out of the _Belt_, he persuaded himself, that it was rather a _Sally_, or
_Prominency_ of the _Belt_, than a round _shadow_, as that of a _Satellite_
of _Jupiter_ must have bin. But having been since informed of _all_ the
_Observations_ made by _Cassini_ and _Campani_, with the _New_ Glasses, and
seen his _Figure_, he candidly and publickly wisheth, that he had not
spoken of that _Sally_, or _Prominency_; advowing that he can doubt no
longer, but that it was the _shadow_ of the _Satellit_ between _Jupiter_
and the _Sun_, having seen the other emerge, as soon as with a 20. foot
Glass he made the Observation, and having not perceiv'd these _shadows_
with a 12. foot Glass: But although he grants that they did ghess better
than he, yet he doth it with this _proviso_, _vid._ in case they made
_that_ Observation on of _July_ 30. not with their 36. but 12. or 17. foot
_Telescope_. If it be wondred at, that Monsieur _Auzout_ did not see this
_shadow_ move, he allegeth his indisposition for making _long
Observations_, and addeth, that it may be much more wondred at, that
neither _Campani_ nor himself did see upon the obscure _Belt_ the Bodies of
the _Satellites_, as parts more Luminous than the _Belt_. For (saith he)
although the _Latitude_ was _Meridional_, it being no more than of 9. or
10. minutes, the Body of the _Satellites_ should, thinks he, pass between
_us_ and the _Belt_, especially according to _Campani_, who maketh the
_Belt_ so large, and puts the _shadows_ farr enough within the same. This
maketh him conclude, that either they have not observed well enough, or
that the motion of the _Satellites_ doth not exactly follow the _Belts_,
and is inclin'd unto them. Whereupon he resolves, that when he shall know
that they are to pass between _Jupiter_ and _us_, and to be over against
the _Belt_, that {74} then he will observe, whether he can see them appear
upon the _Belt_, as upon a darker ground, especially, the _third_ of them,
which is sensibly greater, and more Luminous, than the rest. He hopeth
also, that in time, the _shadow_ of _Saturns Moon_ will be seen upon
_Saturn_, although we are yet some years to stay for it, and to prepare
also for better Glasses.
From this rare Observation, he inferrs the _Proportion_ of the _Diameter_
of the _Satellites_ to that of _Jupiter_; and judgeth, that no longer doubt
can be made of the turning of these 4. _Satellites_, or _Moons_ about
_Jupiter_, as our _Moon_ turns about the _Earth_, and after the same way as
the rest of the Celestial Bodies of our _Systeme_ do move: whence also a
strong conjecture may be made, that _Saturns_ Moon turns likewise about
_Saturn_.
Hence he also taketh occasion to intimate, that we need not scruple to
conclude, that if these two _Planets_ have _Moons_ wheeling about them, as
our _Earth_ hath one that moves about it, the conformity of these _Moons_
with our _Moon_, does prove the conformity of our _Earth_ with those
_Planets_, which carrying away their _Moons_ with themselves, do turn about
the _Sun_, and very probably make their _Moons_ turn about them in turning
themselves about their _Axis_; and also, that there is no cause to invent
perplex'd and incredible _Hypotheses_, for the receding from this
_Analogie_ since (saith he) if this be truth, the Prohibitions of
publishing this doctrine, which formerly were caused by the offence of
Novelty, will be laid aside, as one of the most zealous Doctors of the
contrary Opinion hath given cause to hope, witness _Eustachius de Divinis_,
in his _Tract_ against Monsieur _Hugen_'s _Systeme_ of _Saturn_, _p._ 49.
where we are inform'd, that that learned Jesuit, _P. Fabry_, Penitentiary
of S _Peter_ in _Rome_, speaks to this purpose:
Ex vestris, iisque Coryphaeis non semel quaesitum est, utrum aliquam haberent
demonstrationem pro _Terrae motu_ adstruendo. Nunquam ausi sunt id asserere
Nul igitur obstat quin loca illa in sensu literali Ecclesia intelligat, &
intelligenda esse declaret, quamdiu nulla demonstratione contrarium
evincitur; quae si forte aliquando a vobis excogitetur (quod vix crediderim)
in hoc casu nullo modo dubitabit Ecclesia declarare, loca illa in sensu
figurato & improprio intelligenda esse, ut illud Poetae, _Terraeque Urbesque
recedunt_.
_It hath been more than once asked of your Chieftains, whether they had a
Demonstration for asserting the motion of the Earth? They durst never yet
affirm they had; wherefore nothing hinders, but that the Church may
understand those Scripture-places, that speak of this matter, in a
_literal_ sence, and declare they should be so understood, as long as the
contrary is not evinced by any demonstration; {75} which, if perhaps it
should be found out by you (which I can hardly believe it wil) in this case
the Church will not at all scruple to declare, that these places are to be
understood in a figurative and improper sence, according to that of the
Poet, _Terraeque Urbesque recedunt_._
Whence this Author concludes, that the said _Jesuite_ assuring us that the
_inquisition_ hath not _absolutely_ declared, that those Scripture-places
are to be understood _literally_, seeing that the _Church_ may make a
contrary declaration, no man ought to scruple to follow the _Hypothesis_ of
the _Earths motion_, but only forbear to maintain it in _publick_, till the
prohibition be called in. But to return to the matter in hand, this Author,
upon all these observations and relations of _Cassini_ and _Campani_, doth
find no reason to doubt any more of the excellency of the Glass used by
them, above his; except this difference may be imputed to that of the
_Air_, or of the _Eys_. But yet he is rather inclined to ascribe it to the
goodness of their Glasses, and that the rather, because, he would not be
thought to have the vanity of magnifying his own; of which, yet he
intimates by the by, that he caused one to be wrought, of 150 _Parisian_
feet; which though it proved none of the best, yet he despairs not to make
good ones of _that_, and of far greater Length.
* * * * *
__Signor Campani's_ Answer: and Monsieur _Auzout_'s Animadversions
thereon._
The other part of this _French Tract_, conteining _Campani_'s Answer, and
Mr. _Auzout_ his _Reflections_ thereon, begins with the pretended _Shadows_
of the _Ring_ upon _Saturn_, and of _Saturn_ upon the _Ring_. Concerning
which, the said _Campani_ declareth, that he never believed them to be
_shadows_, made by the _Ring_ upon the _Disk_ of _Saturn_, or by the body
of _Saturn_ upon the _Ring_, but the _Rimms_ of these bodies, which being
_unequally_ Luminous, did shew these appearances. In which Explication,
forasmuch as it represents, that the said _Campani_ meant to note only the
_Inequality of the Light_, which, _he saith_, his Glasses did discover, Mr.
_Auzout_ does {76} so far acquiesce, that he only wishes, that his own
Glasses would shew him those differences. Next to the Objection, made by
Monsieur _Auzout_, against Signor _Campani_, touching the Proportion of the
Length of the _Ring_ to its breadth, _Campani_ replyeth, that the Glasses
of Monsieur _Auzout_, shew not all the particulars, that his do, and
therefore are unfit for determining the true Figure and breadth of the
apparent _Ellipsis_ of the _Ring_. To which M. _Auzout_ rejoyns, that he is
displeased at his being destitute of better Glasses, but that it will be
very hard for the future to convince _Campani_ touching the _Proportion_ of
the _Ring_, seing that the breadth of the _Ellipsis_ is always diminishing,
although, if the declination of the _Ring_ remains always the same, one can
at all times know, which may have been its greatest breadth. But he
assures, that the breadth of the _Ring_ is not the half of its length, and
that it doth not spread out so much beyond _Saturn_'s Body, as he hath
alleged. And withal desirs to know, what can be answered by Sig. _Campani_
to M. _Hugens_, who being persuaded, that the Declination of the _Ring_ is
not above 23 deg. 30' having seen the _Ring_ to spread out above the Body
of _Saturn_, concludes, in a Letter to M. _Auzout_, that the length of the
_Ring_ is more than treble the _Diameter_ of _Saturn_'s body, which,
according to _Campani_, is only as about 67 to 31. Which difference yet dos
not appear to M. _Auzout_ to be so great; but that M. _Hugens_ perhaps will
impute it to the Optical reason, which he (_Auzout_) hath alleged of the
Advance of the light upon the obscure space; although he is of Opinion, he
should not have concluded so great a Length, if he had not seen the Breadth
spread out more, than he hath done: for (_saith he_) if the Length of the
_Ring_ be to the body of _Saturn_, 21/2 to 1. and the _Inclination_ be 23
deg. 30' the _Ring_ will be just as large, as the body, without spreading
out; but if the _Ring_ be bigger, it will a little spread out; and if it
were treble, it must needs spread out the half of its breadth, which hath
not so appeared to him.
Further, to M. _Auzout's_ change of Opinion, and believing, that the
_Advance_ or _Sally_, seen by him in _Jupiter_, was the _Shadow_ of one of
his Moons, _Campani_ declares, that he would not have him guilty of that
change: Whereupon M. _Auzout_ wonders, why _Campani_ then hath not marked
it in his _Figure_; and would {77} gladly know, whether that _Sally_ be
more easie to discover, than the _Shadows_ of the _Satellites_, which
_Campani_ believs, _Auzout_ hath not seen; and whether he be assured, that
those obscure parts, which he there distinguishes, do not change: for if
they should not change, then _Jupiter_ would not turn about his _Axis_,
which yet, he saith, it doth, according to the _Observation_ made by Mr.
_Hook_, _May_ 9 1664. inserted in the first papers of these _Transactions_.
The full Discovery of which particular also he makes to be a part of
_Cassini's_ and _Campani_'s work, seeing that they so distinctly see the
inequalities in the _Belts_, and see also sometimes other _Spots_ besides
the _Shadows_ of the _Satellites_: where he exhorts all the Curious, that
have the conveniency of observing, to endeavor the discovery of a matter of
that importance, which would prove one of the greatest _Analogies_ for the
_Earth's Motion_.
* * * * *
_An Account of Mr. _Richard Lower_'s newly published _Vindication_ of
Doctor _Willis_'s _Diatriba_ de _Febribus_._
The Title of this Curious piece, is _Diatribae Thomae Willisii Med. Doct. &
Profess. Oxon. De Febribus Vindicatio, Authore Richardo Lower, &c._ In it
are occasionally discussed many considerable Medical and Anatomical
inquiries, as, Whether a Fever does consist in an Effervescence of Blood?
And if so, of what kind? Whether there be a _Nervous_ and _Nutritious_
Juice? Whether the office of sanguification belongs to the Blood it self,
existing _before_ those _Viscera_ (at least) that are commonly esteemed to
be the Organs of sanguification? How _Nutrition_ is performed, and the
nourishing substance assimilated? Whether the Blood affords both the Matter
for the structure of the Body, and such parts also, as are fit for the
nourishment of the same? Whether the Pulse of the Heart ceasing, there
remains yet a certain Motion in the blood, arguing, that _Pulse_ and _Life_
do ultimately rest in the _Blood_? Whether the Umbilical Vessels convey the
blood of the Mother to the Child, or whether the _Foetus_ be for the most
part form'd and {78} acted by the circulating blood, before the existence
of the Umbilical Vessels, or before the connecting of the _Foetus_ with the
_Uterus_? A new Experiment to prove that the _Chyle_ is not transmuted into
_Blood_ by the _Liver_. A discourse of the Nature of the _Blood_, and what
difference there is between the _Venal_ and _Arterial_ blood, and for what
Uses both the one and the other are particularly designed. Where it is
considered, what _Life_ is, and whence the _Soul_ of _Brutes_, and its
subsistence, and operations do depend. It is also inquired into, what the
uses of the _Lungs_ are in _hot_ Animals? And many other such material
disquisitions are to be found in this small, but very Ingenious and Learned
Treatise.
* * * * *
_A Note touching a Relation, inserted in the last _Transactions_._
In the Experiment of killing _Ratle-Snakes_, mentioned in the last of the
precedent Papers (wherein, by a mistake, these words, _The way_, were put
for _A way_, or _An Experiment_) it should have been added, that the
Gentleman there mention'd, did affirm, that, in those places, where the
Wild _Penny-Royal_ or _Dittany_ grows, no _Ratle-Snakes_ are observed to
come.
* * * * *
_Errata._
Pag. 59. line 11. read, _bignesses_, l. 20. r. _endure_, for, resist. l.
30. r. _those_, for, these. l. 31. r. _Plain_, for, place.
* * * * *
_LONDON,_
Printed with Licence, By _John Martyn_, and _James Allestry_, Printers to
the _Royal-Society_, at the _Bell_ in St. _Pauls Church-Yard_. 1665.
{79}
* * * * *
_Numb._ 5.
PHILOSOPHICAL
_TRANSACTIONS._
* * * * *
_Munday_, _July_ 3. 1665.
* * * * *
The Contents.
_An Account, how _Adits_ and _Mines_ are wrought at _Liege_ without
_Air-shafts_, communicated by Sir _Robert Moray_. A way to break
_easily_ and _speedily_ the hardest _Rocks_; imparted by the same
_Person_, as he received it from Monsieur _Du Son_ the Inventor.
Observables upon a _Monstrous Head_. Observables in the Body of the
Earl of _Belcarres_, sent out of _Scotland_. A Relation of the designed
Progress to be made in the _Breeding of Silk-worms_, and the _Making_
of _Silk_, in _France_. Enquiries touching _Agriculture_, for _Arable_
and _Meadows_._
* * * * *
_An Account, how _Adits_ & _Mines_ are wrought at _Liege_ without
_Air-shafts_, communicated by Sir _Robert Moray_._
It is well known to those conversant in _Mines_, that there is nothing of
greater inconvenience in the working or _driving_, as they call it, of
_Mines_ or _Adits_ under ground, for carrying away of Water, or such
_Minerals_ as the _Mine_ affords, than the _Damp, want,_ and _impurity of
Air,_ that {80} occur, when such _Adits_ are wrought or driven inward upon
a _Level_, or near it, 20, 30, or 40. fathom, more or less. Aswel because
of the expence of money, as of time also, in the _Ordinary_ way of
preventing or remedying those inconveniences; which is, by letting down
_shafts_ from the _day_ (as _Miners_ speak) to meet with the _Adit_; by
which means the Air hath liberty to play through the whole work, and so
takes away bad vapours and furnishes good Air for Respiration. The Expence
of which _shafts_, in regard of their vast depth, hardness of the Rock,
drawing of water, &c. doth sometimes equal, yea exceed the _ordinary_
charge of the whole _Adit_.
Amongst the _Expedients_ that have been devised to remedy this, there is
one practised in the _Coal-mines_, near the Town of _Liege_ (or _Luyck_)
that seems preferable to all others for Efficacy, Ease, and Cheapness: the
description whereof followeth.
At the mouth or entry of the _Adit_ there is a structure raised of _Brick_,
like a _Chimney_, some 28. or 30. foot high in all: at the bottom, two
opposite sides are (or may be) some 51/2 foot broad; and the other two, 5.
foot: the wall 11/2 _Brick_ thick. At the lower part of it, is a hole, some
9. or 10. inches square, for taking out of the Ashes, which when it is
done, this Ash-hole is immediately stopt so close, as Air cannot possibly
get in at any part of it. Then, some 3. foot above ground or more, there is
on that side, that is next to the _Adit_ or Pit, a square hole of 8. or 9.
inches every way, by which the Air enters to make the Fire burn: Into this
hole there is fixed a square _Tube_ or _Pipe_ of Wood, whereof the Joints
and Chinks are so stopt with Parchment pasted or glewed upon them, that the
Air can no where get in to the Pipe but at the end: And this Pipe is still
lengthened, as the _Adit_ or Pit advanceth, by fitting the new Pipes so, as
one end is alwaies thrust into the other, and the Joints and Chinks still
carefully cemented and stopt as before. So the Pipe or Tube being still
carried on, as near as is necessary, to the wall or place, where fresh Air
is requisite; the Fire within the Chimney doth still attract {81} (so to
speak) Air through the Tube, without which it cannot burn, which yet it
will do, as is obvious to conceive (all Illustrations and Philosophical
Explications being here superfluous,) and so, while the Air is drawn by the
fire from the farthest or most inward part of the _Mine_ or _Adit_, fresh
Air must needs come in from without to supply the place of the other, which
by its motion doth carry away with it all the ill vapors, that breath out
of the ground; by which meanes the whole _Adit_ will be alwaies filled with
fresh Air, so that men will there breath as surely as abroad, and not only
Candles burn, but Fire, when upon occasion there is use for it for breaking
of the Rock.
Now that there may be no want of such fresh Air, the Fire must alwaies be
kept burning in the Chimney, or at least as frequently as is necessary: For
which purpose there must be two of the Iron Grates or Chimneys, that when
any accident befals the one, the other may be ready to be in its place, the
Coals being first well kindled in it: but when the fire is neer spent, the
Chimney or Grate being haled up to the dore, is to be supplied with fresh
fuel.
The Figure of the Fabrick, Chimney, and all the parts thereof being
hereunto annexed, the rest will be easily understood.
[Illustration]
_Figure_ 1.
A. The _Hole_ for taking out the Ashes.
B. The _Square-hole_, into which the Tube or Pipe for conveying the Air is
to be fixed.
C. The _Border_ or _Ledge_ of _Brick_ or _Iron_, upon which the
_Iron-grate_ or _Cradle_, that holds the burning Coals, is to rest, the one
being exactly fitted for the other.