Experiments and Considerations Touching Colours (1664) by Robert Boyle

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Greater probability there is, That the Principal Cause (for I would not
exclude all concurrent ones) of the Blackness of _Negroes_ is some Peculiar
and Seminal Impression, for not onely we see that _Blackmore_ boyes brought
over into these Colder Climates lose not their Colour; But good Authors
inform us, That the Off-spring of _Negroes_ Transplanted out of _Africa_,
above a hundred years ago, retain still the Complexion of their
Progenitors, though possibly in Tract of time it will decay; As on the
other side, the White people removing into very Hot Climates, have their
Skins by the Heat of the Sun scorch'd into Dark Colours; yet neither they,
nor their Children have been observ'd, even in the Countreys of _Negroes_,
to descend to a Colour amounting to that of the Natives; whereas I remember
I have Read in _Pisos_[11] excellent account of _Brasile_, that betwixt the
_Americans_ and _Negroes_ are generated a distinct sort of Men, which they
call _Cabocles_, and betwixt _Portugalls_ and _AEthiopian_ women, He tells
us, he has sometimes seen Twins, whereof one had a White skin, the other a
Black; not to mention here some other instances, he gives, that the
productions of the mixtures of differing people, that is (indeed,) the
effects of Seminal Impressions which they consequently argue to have been
their Causes; and we shall not much scruple at this, if we consider, that
even Organical parts may receive great Differences from such peculiar
Impressions, upon what account soever they came to be setled in the first
Individual persons, from whom they are Propogated to Posterity, as we see
in the Blobber-Lips and Flat-Noses of most Nations of _Negroes_. And if we
may Credit what Learned men deliver concerning the Little Feet of the
_Chinesses_, the _Macrocephali_ taken notice of by _Hippocrates_, will not
be the only Instance we might apply to our present purpose. And on this
occasion it will not perchance be Impertinent to add something of what I
have observ'd in other Animals, as that there is a sort of Hens that want
Rumps; And that (not to mention that in several places there is a sort of
Crows or Daws that are not Cole-black as ours, but partly of a Whitish
Colour) in spight of _Porphyries_ examples of Inseparable Accidents, I have
seen a perfectly White Raven, as to Bill as well as Feathers, which I
attentively considered, for fear of being impos'd upon. And this recalls
into my Memory, what a very Ingenious Physician has divers times related to
me of a young Lady, to whom being call'd, he found that though she much
complain'd of want of Health, yet there appear'd so little cause either in
her Body, or her Condition to Guess that She did any more than fancy her
self Sick, that scrupling to give her Physick, he perswaded her Friends
rather to divert her Mind by little Journeys of Pleasure, in one of which
going to Visit St. _Winifrids_ Well, this Lady, who was a _Catholick_, and
devout in her Religion, and a pretty while in the Water to perform some
Devotions, and had occasion to fix her Eyes very attentively upon the Red
pipple-stones, which in a scatter'd order made up a good part of those that
appear'd through the water, and a while after growing Bigg, she was
deliver'd of a Child, whose White Skin was Copiously speckl'd with spots of
the Colour and Bignesss of those Stones, and though now this Child have
already liv'd several years, yet she still retains them. I have but two
things to add concerning the Blackness of _Negroes_, the one is, that the
Seat of that Colour seems to be but the thin _Epidermes_, or outward Skin,
for I knew a young _Negroe_, who having been lightly Sick of the Small Pox
or Measles, (for it was doubted which of the two was his Disease) I found
by enquiry of a person that was concern'd for him, that in those places
where the little Tumors had broke their passage through the Skin, when they
were gone, they left Within specks behind them; And the lately commended
_Piso_ assures us, that having the opportunity in _Brasil_ to Dissect many
_Negroes_, he cleerly found that their Blackness went no deeper than the
very outward Skin, which _Cuticula_ or _Epidermis_ being remov'd, the
undermost Skin or _Cutis_ appear'd just as White as that of _Europaean_
Bodyes. And the like has been affirmed to me by a Physician of our own,
whom, hearing he had Dissectcd a _Negroe_ here in _England_, I consulted
about this particular. The other thing to be here taken notice of
concerning _Negroes_ is, That having enquir'd of an Intelligent
acquaintance of mine (who keeps in the _Indies_ about 300. of them as well
Women as Men to work in his Plantations,) whether their Children come Black
into the world; he answer'd, That they did not, but were brought forth of
almost the like Reddish Colour with our _European_ Children; and having
further enquir'd, how long it was before these Infants appear'd Black, be
reply'd, that 'twas not wont to be many daies. And agreeable to this
account I find that, given us in a freshly publish'd French Book written by
a _Jesuit_, that had good opportunity of Knowing the Truth of what he
Delivers, for being one of the Missionaries of his Order into the Southern
_America_ upon the Laudable Design of Converting Infidels to Christianity,
he Baptiz'd several Infants, which when newly Born, were much of the same
Colour with _European_ Babes, but within about a Week began to appear of
the Hue of their Parents. But more Pregnant is the Testimony of our
Countrey-man _Andrew Battel_, who being sent Prisoner by the _Portugalls_
to _Angola_, liv'd there, and in the adjoyning Regions, partly as a
Prisoner, partly as a Pilot, and partly as a Souldier, near 18. years, and
he mentioning the _African_ Kingdom of _Longo_, peopl'd with Blacks, has
this passage:[12] _The Children in this Countrey are Born White, and change
their Colour in two dayes to a Perfect Black_. As for Example, _The_
Portugalls _which dwell in the Kingdome of_ Longo _have sometimes Children
by the_ Negroe_-women, and many times the Fathers are deceived, thinking,
when the Child is Born, that it is theirs, and within two dayes it proves
the Son or Daughter of a_ Negroe,_ which the_ Portugalls _greatly grieve
at_; And the same person has elsewhere a Relation, which, if he have made
no use at all of the liberty of a Traveller, is very well worth our Notice,
since this, together with that we have formerly mention'd of Seminal
Impressions, shews a possibility, that a Race of _Negroes_ might be begun,
though none of the Sons of _Adam_, for many Precedent Generations were of
that Complexion. For I see not why it should not be at least as possible,
that White Parents may sometimes have Black Children, as that _African
Negroes_ should sometimes have lastingly White ones, especially since
concurrent causes may easily more befriend the Productions of the Former
kind, than under the scorching Heat of _Africa_ those of the Latter. And I
remember on the occasion of what he delivers, that of the White Raven
formerly mention'd, the Possessor affirm'd to me, that in the Nest out of
which he was taken White, they found with him but one other Young one, and
that he was of as Jetty a Black as any common Raven. But let us hear our
Author himself[13]; _Here are_ (sayes he, speaking of the formerly
mention'd Regions) _Born in this Countrey White Children, which is very
rare among them, for their Parents are_ Negroes; _And when any of them are
Born, they are presented to the King, and are call'd_ Dondos; _these are as
White as any White Men. These are the Kings Witches, and are brought up in
Witchcraft, and alwayes wait on the King: There is no man that dare meddle
with these_ Dondos, _if they go to the Market they may take what they lift,
for all Men stand in awe of them. The King of_ Longo _hath four of them_.
And yet this Countrey in our Globes is plac'd almost in the midst of the
Torrid Zone (four or five Degrees Southward of the Line.) And our Author
elsewhere tells us of the Inhabitants, that they are so fond of their
Blackness, that they will not suffer any that is not of that Colour (as the
_Portugalls_ that come to Trade thither) to be so much as Buri'd in their
Land, of which he annexes a particular example,[14] that may be seen in his
Voyage preserv'd by our Industrious Countreyman Mr. _Purchas_. But it is
high time for me to dismiss Observations, and go on with Experiments.

[11] _Piso_ Nat. & Med. Hist. _Brasil. lib_ 1. in fine.

[12] _Purchas_ Pilgrim. Second part, Seventh Book 3. Chap. Sect 5.

[13] _Purchas_. Ibid.

[14] _Purchas_ Ibid. in fin

_EXPERIMENT XII._

The way, _Pyrophilus,_ of producing Whiteness by Chymical Praecipitations is
very well worth our observing, for thereby Bodyes of very Differing Colours
as well as Natures, though dissolv'd in Several Liquors, are all brought
into _Calces_ or Powders that are White. Thus we find that not only
Crabs-eyes, that are of themselves White, and Pearls that are almost so,
but _Coral_ and _Minium_ that are Red, being dissolv'd in Spirit of
Vinegar, may be uniformly Praecipitated by Oyl of _Tartar_ into White
Powders. Thus Silver and Tin separately dissolv'd in _Aqua Fortis_, will
the one Praecipitate it self, and the other be Praecipitated by common
Salt-water into a White _Calx_, and so will Crude Lead and Quicksilver
first dissolv'd likewise in _Aqua Fortis_. The like _Calx_ will be afforded
as I have try'd by a Solution of that shining Mineral Tinglass dissolv'd in
_Aqua Fortis_, and Praecipitated out of it; and divers of these _Calces_ may
be made at least as Fair and White, if not better Colour'd, if instead of
Oyl of _Tartar_ they were Praecipitated with Oyl of _Vitriol_, or with
another Liquor I could Name. Nay, that Black Mineral _Antimony_ it self,
being reduc'd by and with the Salts that concurr to the Composition of
common Sublimate, into that Cleer though Unctuous Liquor that Chymists
commonly call Rectifi'd Butter of _Antimony_, will by the bare affusion of
store of Fair Water be struck down into that Snow-white Powder, which when
the adhering Saltness is well wash'd off, Chymists are pleas'd to call
_Mercurius Vitae_, though the like Powder may be made of _Antimony_, without
the addition of any _Mercury_ at all. And this Lactescence if I may so call
it, does also commonly ensue when Spirit of Wine, being Impregnated with
those parts of Gums or other Vegetable Concretions, that are suppos'd to
abound with Sulphureous Corpuscles, fair Water is suddenly pour'd upon the
Tincture or Solution. And I remember that very lately I did, for Tryal
sake, on a Tincture of _Benjamin_ drawn with Spirit of Wine, and brought to
be as Red as Blood, pour some fair Water, which presently mingling with the
Liquor, immediately turn'd the whole Mixture White. But if such Seeming
Milks be suffer'd to stand unstirr'd for a convenient while, they are wont
to let fall to the bottome a Resinous Substance, which the Spirit of Wine
Diluted and Weakned by the Water pour'd into it was unable to support any
longer. And something of Kin to this change of Colour in Vegetables is
that, which Chymists are wont to observe upon the pouring of Acid Spirits
upon the Red Solution of _Sulphur_, dissolv'd in an Infusion of Pot-ashes,
or in some other sharp _Lixivium_, the Praecipitated _Sulphur_ before it
subsides, immediately turning the Red Liquor into a White one. And other
Examples might be added of this way of producing Whiteness in Bodyes by
Praecipitating them out of the Liquors wherein they have been Dissolv'd; but
I think it may be more usefull to admonish you, _Pyrophilus_, that this
observation admits of Restrictions, and is not so Universal, as by this
time perhaps you have begun to think it; For though most Praecipitated
Bodyes are White, yet I know some that are not; For Gold Dissolv'd in _Aqua
Regis_, whether you Praecipitate it with Oyl of _Tartar_, or with Spirit of
_Sal Armoniack_, will not afford a White but a Yellow _Calx_. _Mercury_
also though reduc'd into Sublimate, and Praecipitated with Liquors abounding
with Volatile Salts, as the Spirits drawn from Urine, Harts-horn, and other
Animal substances, yet will afford, as we Noted in our first Experiment
about Whiteness and Blackness, a White Praecipitate, yet with some Solutions
hereafter to be mentioned, it will let fall an Orange-Tawny Powder. And so
will Crude _Antimony_, if, being dissolv'd in a strong Lye, you pour (as
farr as I remember) any Acid Liquor upon the Solution newly Filtrated,
whilst it is yet Warm. And if upon the Filtrated Solution of _Vitriol_, you
pour a Solution of one of these fix'd Salts, there will subside a Copious
substance, very farr from having any Whiteness, which the Chymists are
pleas'd to call, how properly I have elsewhere examin'd, the _Sulphur of
Vitriol_. So that most part of Dissolv'd Bodyes being by Praecipitation
brought to White Powders, and yet some affording Praecipitates of other
Colours, the reason of both the Phaenomena may deserve to be enquir'd into.

_EXPERIMENT XIII._

Some Learned Modern Writers[15] are of Opinion, that the Account upon which
Whiteness and Blackness ought to be call'd, as they commonly are, the two
Extreme Colours, is, That Blackness (by which I presume is meant the Bodyes
endow'd with it) receives no other Colours; but Whiteness very easily
receives them all; whence some of them compare Whiteness to the
_Aristotelian Materia prima_, that being capable of any sort of Forms, as
they suppose White Bodyes to be of every kind of Colour. But not to Dispute
about Names or Expressions, the thing it self that is affirm'd as Matter of
Fact, seems to be True enough in most Cases, not in all, or so, as to hold
Universally. For though it be a common observation among Dyers, That
Clothes, which have once been throughly imbu'd with Black, cannot so well
afterwards be Dy'd into Lighter Colours, the praeexistent Dark Colour
infecting the Ingredients, that carry the Lighter Colour to be introduc'd,
and making it degenerate into Some more Sad one; Yet the Experiments lately
mention'd may shew us, that where the change of Colour in Black Bodies is
attempted, not by mingling Bodyes of Lighter Colours with them, but by
Addition of such things as are proper to alter the Texture of those
Corpuscles that contain the Black Colour, 'tis no such difficult matter, as
the lately mention'd Learned Men imagine, to alter the Colour of Black
Bodyes. For we saw that Inks of several Kinds might in a trice be depriv'd
of all their Blackness; and those made with Logwood and Red-Roses might
also be chang'd, the one into a Red, the other into a Reddish Liquor; and
with Oyl of _Vitriol_ I have sometimes turn'd Black pieces of Silk into a
kind of Yellow, and though the Taffaty were thereby made Rotten, yet the
spoyling of that does no way prejudice the Experiment, the change of Black
Silk into Yellow, being never the less True, because the Yellow Silk is the
less good. And as for Whiteness, I think the general affirmation of its
being so easily Destroy'd or Transmuted by any other Colour, ought not to
be receiv'd without some Cautions and Restrictions. For whereas, according
to what I formerly Noted, Lead is by Calcination turned into that Red
Powder we call _Minium_; And Tin by Calcination reduc'd to a White _Calx_,
the common Putty that is sold and us'd so much in Shops, instead of being,
as it is pretended and ought to be, only the _Calx_ of Tin, is, by the
Artificers that make it, to save the charge of Tin, made, (as some, of
themselves have confess'd, and as I long suspected by the Cheap rate it may
be bought for) but of half Tin and half Lead, if not far more Lead than
Tin, and yet the Putty in spight of so much Lead is a very White Powder,
without disclosing any mixture of _Minium_. And so if you take two parts of
Copper, which is a High-colour'd Metall, to but one of Tin, you may by
Fusion bring them into one Mass, wherein the Whiteness of the Tin is much
more Conspicuous and Predominant than the Reddishness of the Copper. And on
this occasion it may not be Impertinent to mention an Experiment, which I
relate upon the Credit of a very Honest man, whom I purposely enquir'd of
about it, being my self not very fond of making Tryals with _Arsenick_, the
Experiment is this, That if you Colliquate _Arsenick_ and Copper in a due
proportion, the _Arsenick_ will Blanch the Copper both within and without,
which is an Experiment well enough Known; but when I enquir'd, whether or
no this White mixture being skilfully kept a while upon the Cupel would not
let go its _Arsenick_, which made Whiteness its praedominant Colour, and
return to the Reddishness of Copper, I was assur'd of the Affirmative; so
that among Mineral Bodyes, some of those that are White, may be far more
capable, than those I am reasoning with seem to have known, of Eclipsing
others, and of making their Colour Praedominant in Mixtures. In further
Confirmation of which may be added, that I remember that I also took a lump
of Silver and Gold melted together, wherein by the AEstimate of a very
Experienced Refiner, there might be about a fourth or third part of Gold,
and yet the Yellow Colour of the Gold was so hid by the White of the
Silver, that the whole Mass appear'd to be but Silver, and when it was
rubb'd upon the Touchstone, an ordinary beholder could scarce have
distinguish'd it from the Touch of common Silver; though if I put a little
_Aqua Fortis_ upon any part of the White Surface it had given the
Touchstone, the Silver in the moistned part being immediately taken up and
conceal'd by the Liquor, the Golden Particles would presently disclose that
native Yellow, and look rather as if Gold, than if the above mention'd
mixture, had been rubb'd upon the Stone.

[15] See _Scaliger_ Exercit. 325. Sect. 9.

_EXPERIMENT XIV._

I took a piece of Black-horn, (polish'd as being part of a Comb) this with
a piece of broken glass I scrap'd into many thin and curdled flakes, some
shorter and some longer, and having laid a pretty Quantity of these
scrapings together, I found, as I look'd for, that the heap they compos'd
was White, and though, if I laid it upon a clean piece of White Paper, its
Colour seem'd somewhat Eclips'd by the greater Whiteness of the Body it was
compar'd with, looking somewhat like Linnen that had been sulli'd by a
little wearing, yet if I laid it upon a very Black Body, as upon a Beaver
Hatt, it then appear'd to be of a good White, which Experiment, that you
may in a trice make when you please, seems very much to Disfavour both
their Doctrine that would have Colours to flow from the Substantial Forms
of Bodyes, and that of the Chymists also, who ascribe them to one or other
of their three Hypostatical Principles; for though in our Case there was so
great a Change made, that the same Body without being substantially either
Increas'd or Lessened, passes immediately from one extreme Colour to
another (and that too from Black to White) yet this so great and sudden
change is effected by a slight Mechanical Transposition of parts, there
being no Salt or _Sulphur_ or _Mercury_ that can be pretended to be Added
or Taken away, nor yet any substantial Form that can reasonably be suppos'd
to be Generated and Destroy'd, the Effect proceeding only from a Local
Motion of the parts which so vary'd their Position as to multiply their
distinct Surfaces, and to Qualifie them to Reflect far more Light to the
Eye, than they could before they were scrap'd off from the entire piece of
Black horn.

_EXPERIMENT XV._

And now, _Pyrophilus_, it will not be improper for us to take some notice
of an Opinion touching the cause of Blackness, which I judged it not so
seasonable to Question, till I I had set down some of the Experiments, that
might justifie my dissent from it. You know that of late divers Learned
Men, having adopted the three Hypostatical Principles, besides other
Notions of the Chymists, are very inclinable to reduce all Qualities of
Bodies to one or other of those three Principles, and Particularly assign
for the cause of Blackness the Sootie steam of _adust_ or _torrifi'd
Sulphur_. But I hope that what we have deliver'd above to countenance the
Opinion we have propos'd about the Cause of Blackness, will so easily
supply you with several Particulars that may be made use of against this
Opinion, that I shall now represent to You but two things concerning it.

And First it seems that the favourers of the Chymicall Theories might have
pitcht upon some more proper term, to express the Efficient of Blackness
than _Sulphur adust_; for we know that _common Sulphur_, not only when
Melted, but even when Sublim'd, does not grow Black by suffering the Action
of the fire, but continues and ascends Yellow, and rather more than less
White, than it was before its being expos'd to the fire. And if it be set
on fire, as when we make that acid Liquor, that Chymists call _Oleum
Sulphuris per campanam_, it affords very little Soot, and indeed the flame
yeelds so little, that it will scarce in any degree Black a sheet of White
Paper, held a pretty while over the flame and smoak of it, which is
observed rather to Whiten than Infect linnen, and which does plainly make
Red Roses grow very Pale, but not at all Black, as far as the Smoak is
permitted to reach the leaves. And I can shew you of a sort of fixt Sulphur
made by an Industrious Laborant of your acquaintance, who assur'd me that
he was wont to keep it for divers weeks together night and day in a naked
and Violent fire, almost like that of the Glass-house, and when, to
satisfie my Curiosity, I made him take out a lump of it, though it were
glowing hot (and yet not melted,) it did not, when I had suffered it to
cool, appear Black, the true Colour of it being a true Red. I know it may
be said, that _Chymists_ in the Opinion above recited mean the _Principle
of Sulphur_, and not _common Sulphur_ which receives its name, not from its
being _all_ perfectly of a Sulphureous Nature, but for that _plenty_ and
_Predominancy_ of the Sulphureous Principle in it. But allowing this, 'tis
easie to reply, that still according to this very Reason, torrifi'd Sulphur
should afford more Blackness, than most other concretes, wherein that
Principle is confess'd to be far less copious. Also when I have expos'd
Camphire to the fire in Close Vessels, as Inflamable, and consequenly
(according to the Chymists) as Sulphureous a Body as it is, I could not by
such a degree of Heat, as brought it to Fusion, and made it Boyl in the
glass, impress any thing of Blackness, or of any other Colour, than its own
pure White, upon this Vegetable concrete. But what shall we say to Spirit
of Wine, which being made by a Chymical Analysis of the Liquor that affords
it, and being totally Inflamable, seems to have a full right to the title
they give it of _Sulphur Vegetabile_, & yet this fluid Sulphur not only
contracts not any degree of Blackness by being often so heated, as to be
made to Boyl, but when it burns away with an Actual flame, I have not found
that it would discolour a piece of White Paper held over it, with any
discernable soot. Tin also, that wants not, according to the Chymists, a
_Sulphur Joviale_, when throughly burned by the fire into a _Calx_, is not
Black, but eminently White. And I lately noted to you out of _Bellonius_,
that the Charcoals of Oxy-cedar are not of the former of these two Colours,
but of the latter. And the Smoak of our Tinby coals here in _England_, has
been usually observ'd, rather to Blanch linnen then to Black it. To all
which, other Particulars of the like nature might be added, but I rather
choose to put you in mind of the third Experiment, about making Black
Liquors, or Inks, of Bodies that were non of them Black before. For how can
it be said, that when those Liquors are put together actually Cold, and
continue so after their mixture, there intervenes any new _Adustion of
Sulphur_ to produce the emergent Blackness? (and the same question will be
appliable to the Blackness produc'd upon the blade of a Knife, that has cut
Lemmons and some kind of Sowr apples, if the juyce (though both Actually
and Potentially Cold) be not quickly wip'd of) And when by the instilling
either of a few drops of Oyl of Vitriol as in the second Experiment, or of
a little of the Liquor mention'd in the Passage pointed at in the fourth
Experiment, (where I teach at once to Destroy one black Ink, and make
another) the Blackness produc'd by those Experiments is presently
destroy'd; if the Colour proceeded only from the Plenty of Sulphurous
parts, torrify'd in the Black Bodies, I demand, what becomes of them, when
the Colour so suddenly dissappears? For it cannot Reasonably be said, that
all those that suffic'd to make so great a quantity of Black Matter, should
resort to so very small a proportion of the Clarifying Liquor, (if I may so
call it) as to be deluted by it, with out at all Denigrating it. And if it
be said that the Instill'd Liquor dispers'd those Black Corpuscles, I
demand, how that Dispersion comes to destroy their Blackness, but by making
such a Local Motion of their parts, as destroys their former Texture? which
may be a Matter of such moment in cases like ours, that I remember that I
have in few houres, without addition, from Soot it self, attain'd pretty
store of Crystalline Salt, and good store of Transparent Liquor, and (which
I have on another occasion noted as remarkable) this so Black Substance had
its Colour so alter'd, by the change of Texture it receiv'd from the fire,
wherewith it was distill'd, that it did for a great while afford such
plenty of very white Exhalations, that the Receiver, though large, seem'd
to be almost fill'd with Milk.

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