3 Yea, that you may not think mee too reſerv'd, or look upon an Enquiry made up of meer Narratives, as ſomewhat jejune, am content to premiſe a few conſiderations, that now offer themſelves to my thoughts, which relate in a more general way, either to the Nature of Colours, or to the ſtudy of it. And I ſhall inſert an Eſſay, as well Speculative as Hiſtorical, of the Nature of Whiteneſs and Blackneſs, that you may have a Specimen of the Hiſtory of Colours, I have ſometimes had thoughts of; and if you diſlike not the Method I have made uſe of, I hope, you, and ſome of the Virtuoſi, your friends, may be thereby invited to go thorow with Red, Blew, Yellow, and the reſt of the particular Colours, as I have done with White and Black, but with farr more ſagacity and ſucceſs. And if I can invite Ingenious men to undertake ſuch Tasks, I doubt not but the Curious will quickly obtain a better Account of Colours, than as yet we have, ſince in our Method the Theorical part of the Enquiry being attended, and as it were interwoven with the Hiſtorical, whatever becomes of the diſputable Conjectures, the Philoſophy of Colours will be promoted by the indiſputable Experiments.
CHAP. II.
1 To come then in the firſt place to our more general Conſiderations, I ſhall begin with ſaying ſomething as to the Importance of examining the Colours of Bodies. For there are ſome, eſpecially Chymiſts, who think, that a conſiderable diverſity of Colours does conſtantly argue an equal diverſity of Nature, in the Bodies wherein it is conſpicuous; but I confeſs I am not altogether of their mind; for not to mention changeable Taffaties, the blew and golden necks of Pidgeons, and divers Water-fowl, Rainbows Natural and Artificial, and other Bodies, whoſe Colours the Philoſophers have been pleaſed to call not Real, but Apparent and Phantaſtical; not to inſiſt on theſe, I ſay, (for fear of needleſly engaging in a Controverſie) we ſee in Parrots, Goldfinches, and divers other Birds, not only that the contiguous feathers which are probably as near in properties as place, are ſome of them Red, and others White, ſome of them Blew, & others Yellow, &c. but that in the ſeveral parts of the ſelf-ſame feather there may often be ſeen the greateſt diſparity of Colours; and ſo in the leaves of Tulips, July-flowers, and ſome other Vegetables
the ſeveral leaves, and even the ſeveral parts of the ſame leaf, although no difference have been obſerved in their other properties, are frequently found painted with very different Colours. And ſuch a variety we have much more admired in that lovely plant which is commonly, and not unjuſtly call'd the Marvayl of Peru; for of divers ſcores of fine Flowers, which in its ſeaſon that gaudy Plant does almoſt daily produce, I have ſcarce taken notice of any two that were dyed perfectly alike. But though Pyro: ſuch things as theſe, among others, keep mee from daring to affirm, that the Diverſity and change of Colours does alwaies argue any great difference or alteration, betwixt, or in, the Bodies, wherein it is to be diſcerned, yet that oftentimes the Alteration of Colours does ſignifie conſiderable Alterations in the diſpoſition of parts of Bodies, may appear in the Extraction of Tinctures, and divers other Chymical Operations, wherein the change of Colours is the chief, and ſometimes the only thing, by which the Artiſt regulates his proceeding, and is taught to know when 'tis ſeaſonable for him to leave off. Inſtances of this ſort are more obvious in divers ſorts of fruits, as Cherries, Plums, &c. wherein, according as the Vegetable ſap is ſweetned, or otherwiſe
ripened, by paſſing from one degree to another of Maturation, the external part of the fruit paſſes likewiſe from one to another Colour. But one of the nobleſt Inſtances I have met with of this kind, is not ſo obvious; and that is the way of tempering Steel to make Gravers, Drills, Springs, and other Mechanical Inſtruments, which we have divers times both made Artificers practiſe in our preſence, and tryed our ſelves, after the following manner, Firſt, the ſlender Steel to be tempered is to be hardened by heating as much of it as is requiſite among glowing Coals, till it be glowing hot, but it muſt not be quenched aſſoon as it is taken from the fire (for that would make it too brittle, and ſpoil it) but muſt be held over a baſon of water, till it deſcend from a White heat to a Red one, which aſſoon as ever you perceive, you muſt immediately quench as much as you deſire to harden in the cold water. The Steel thus hardened, will, if it be good, look ſomewhat White and muſt be made bright at the end, that its change of Colours may be there conſpicuous; and then holding it ſo in the flame of a Candle, that the bright end may be, for about half an inch, or more, out of the flame, that the ſmoak do not ſtain or ſully the brightneſs of it, you ſhall after a
while ſee that clean end, which is almoſt contiguous to the flame, paſs very nimbly from one Colour to another, as from a brighter Yellow, to a deeper and reddiſh Yellow, which Artificers call a ſanguine, and from that to a fainter firſt, and then a a deeper Blew. And to bring home this Experiment to our preſent purpoſe, it is found by daily Experience, that each of theſe ſucceeding Colours argue ſuch a change made in the texture of the Steel, that if it be taken from the flame, and immediately quenched in the tallow (whereby it is ſetled in whatever temper it had before) when it is Yellow, it is of ſuch a hardneſs as makes it fit for Gravers Drills, and ſuch like tools; but if it be kept a few minutes longer in the flame till it grow Blew, it becomes much ſofter, and unfit to make Gravers for Metalls, but fit to make Springs for Watches, and ſuch like Inſtruments, which are therefore commonly of that Colour; and if the Steel be kept in the flame, after that this deep Blew hath diſcloſed it ſelf, it will grow ſo ſoft, as to need to be new hardened again, before it can be brought to a temper, fit for Drills or Penknives. And I confeſs Pyro. I have taken much pleaſure to ſee the Colours run along from the parts of the Steel contiguous to the flame, to the end of the Inſtrument,
and ſucceed one another ſo faſt, that if a man be not vigilant, to thruſt the Steel into the tallow at the very nick of time, at which it has attain'd its due Colour, he ſhall miſs of giving his tool the right temper. But becauſe the flame of a Candle is offenſive to my weak eyes, and becauſe it is apt to either black or ſully the contiguous part of the Steel which is held in it, and thereby hinder the change of Colours from being ſo long and clearly diſcern'd, I have ſometimes made this Experiment by laying the Steel to be tempered upon a heated bar of Iron, which we finde alſo to be employ'd by ſome Artificers in the tempering of ſuch great Inſtruments, as are too big to be ſoon heated ſufficiently by the flame of a Candle. And you may eaſily ſatisfie your ſelf Pyro: of the differing hardneſs and toughneſs, which is aſcribed to Steel temper'd at different Colours, if you break but ſome ſlender wires of Steel ſo temper'd, and obſerve how they differ in brittleneſs, and if with a file you alſo make tryal of their various degrees of hardneſs.