And indeed, there seem to be so few bodies in the world that are _in minimis_ opacous, that I think one may make it a rational _Query_, Whether there be any body absolutely thus _opacous_? For I doubt not at all (and I have taken notice of very many circumstances that make me of this mind) that could we very much improve the _Microscope_, we might be able to see all those bodies very plainly transparent, which we now are fain onely to ghess at by circumstances. Nay, the Object Glasses we yet make use of are such, that they make many transparent bodies to the eye, seem _opacous_ through them, which if we widen the Aperture a little, and cast more light on the objects, and not charge the Glasses so deep, will again disclose their transparency. Now, as for all kinds of colours that are dissolvable in Water, or other liquors, there is nothing so manifest, as that all those ting’d liquors are transparent; and many of them are capable of being _diluted_ and compounded or mixt with other colours, and divers of them are capable of being very much chang’d and heightned, and fixt with several kinds of _Saline menstruums_. Others of them upon compounding, destroy or vitiate each others colours, and _precipitate_, or otherwise very much alter each others tincture. In the true ordering and _diluting_, and deepning, and mixing, and fixing of each of which, consists one of the greatest mysteries of the Dyers; of which particulars, because our _Microscope_ affords us very little information, I shall add nothing more at present; but onely that with a very few tinctures order’d and mixt after certain ways, too long to be here set down, I have been able to make an appearance of all the various colours imaginable, without at all using the help of _Salts_, or _Saline menstruums_ to vary them. As for the mutation of Colours by _Saline menstruums_, they have already been so fully and excellently handled by the lately mention’d Incomparable _Authour_, that I can add nothing, but that of a multitude of trials that I made, I have found them exactly to agree with his Rules and Theories; and though there may be infinite instances, yet may they be reduc’d under a few Heads, and compris’d within a very few Rules. And generally I find, that _Saline menstruums_ are most operative upon those colours that are Purple, or have some degree of Purple in them, and upon the other colours much less. The _spurious_ pulses that compose which, being (as I formerly noted) so very neer the middle between the true ones, that a small variation throws them both to one side, or both to the other, and so consequently must make a vast mutation in the formerly appearing Colour. * * * * * Observ. XI. _Of _Figures_ observ’d in small Sand._